Retinoscopy

RETINOSCOPY
By Dr. Mohamed A.A Etarshawi
M.D Ophthalmology

HISTORY OF THE RETINOSCOPE
• The observations that led to clinical <
retinoscopy> were made in 1859 with a plane
mirror ophthalmoscope lighted by a candle,
when Sir William Bowman noted a linear
shadow seen when examining an astigmatic
eye.
• By 1875, the optics were explained and the
procedure was described as a “shadow test,”
an allusion ‫إشارة‬ . ‫إلماع‬ to neutralization. H.
Parent coined the term <retinoscopy> in 1881

• The earliest retinoscopes used a mirror to
reflect a candle, which produced a “spot” of
light. It was soon discovered that a linear
streak of light could be produced with slit-
shaped mirrors.
• Early electric retinoscopes used spiral
filament bulbs and a rotating slit. Jacob
Copeland introduced a linear filament bulb
that produced a sharp, bright line of light.
The Copeland streak retinoscope set the
standard for future retinoscopic
developments.

OPTICS OF THE RETINOSCOPE
• The streak retinoscope has supplanted ‫ل‬ّ ‫م‬ ‫ح‬ِ‫ّل‬ ‫ي‬َ‫ّلِح‬
‫ل ه‬ّ ‫م‬‫ح‬َ‫ّلِح‬ ‫م‬َ‫ّلِح‬ the spot retinoscope in the modern eye
clinic, and only the streak retinoscope is
discussed in this chapter.
• Although the various brands ‫ماركة‬ of streak
retinoscopes differ in design, they all work
similarly. Light is produced by a luminous
filament within the base of the handle and
emanates from a mirror in the head as a
linear streak, with both orientation‫ج ه‬ُّ‫ه‬ ‫و‬َ‫ّلِح‬ ‫ت‬َ‫ّلِح‬ ; and
vergence ‫إنحدار‬ ، ‫ميل‬ controlled by the
retinoscopist.

• The streak of light passes through the
patient's tear film, cornea, anterior chamber,
lens, vitreous chamber, and retina. It is then
reflected from the choroid and retinal
pigment epithelium as a linear red reflex that
passes back through the sensory retina,
vitreous, lens, aqueous, cornea, and tear
film, through the air between the patient and
the examiner, and into the head of the
retinoscope, through an aperture in the
mirror.

• Finally exiting through the back of the
retinoscope into the retinoscopist's
own eye.
• By observing qualities of the reflected
light (the reflex) after it leaves the
patient's eye, the retinoscopist can
make determinations about the
patient's refractive state.

streak retinoscope
Diagrammatic cross-section of streak retinoscope

Diagrammatic cross-section of streak
retinoscope.
• Light from the filament passes through the
lens to the mirror, where it is reflected
toward the patient. The examiner views
through the aperture behind the mirror.
• The arrows represent the two controllable
functions. The curved arrow indicates that
the bulb may be rotated. The straight arrow
indicates that the vergence of the light rays
may be altered by changing the filament to
lens distance.
• The filament is shown at the focal length of
the lens so that parallel light rays emerge.

• Explaining the optics and proper usage
of the retinoscope can be a confusing
business. To help simplify the text, we
have chosen to use the feminine. ‫ن ث‬ّ ‫م‬‫مؤ‬
‫ضمير‬ pronouns (e.g., “she” and “her”)
when referring to the retinoscopist, and
the masculine ones (e.g., “he,” “him,”
and “his”) when referring to the patient.

• All streak retinoscopes are made of the same
fundamental components: light source,
condensing lens, mirror, and sleeve .
• The light source is a light bulb with a fine,
linear filament, which projects a fine, linear
streak of light with the passage of an electric
current.
• The filament (therefore the streak), can be
rotated 360 degrees by rotating the sleeve of
the retinoscope. Currently, most retinoscopes
use a halogen bulb, which projects a very
bright streak.

• The condensing lens is a plus lens, which
exerts positive vergence on the streak, which
is emitted from the point-source filament in a
highly diverging manner.
• The position of the lens in relation to the
light filament can be altered by raising or
lowering the sleeve.
• In this way, the vergence of the streak that is
emitted from the retinoscope can be
controlled by the retinoscopist, as described
subsequently.

• The mirror bends light that originates in the
handle and is initially projected upward
toward the ceiling, to instead exit the
retinoscope along an axis parallel to the floor
so that it can be projected into the patient's
eye. The mirror should not reflect 100% of
visible light; rather, it must allow some light
to pass through it.
• Only in this way can the retinoscopist have a
view into the patient's pupil that is coaxial
‫المحور‬ ‫متحد‬ to the path of the streak.

CONTROLLING THE PROPERTIES OF THE
RETINOSCOPE
• The basic idea behind the retinoscope is that
the retinoscopist creates a streak of light,
projects it into a patient's eye, bounces it ‫د‬ّ ‫يرت‬
off his retina, and makes deductions ‫استنتاج‬
concerning the patient's refractive status
based on what the image of that streak looks
like when it reaches the retinoscopist's eye.
To aid her in this task, the retinoscopist has
control over, and can easily vary, certain
aspects of the system.

RETINOSCOPE
Two things she can control have nothing to
do with the intrinsic properties of the
retinoscope she is holding:
• The distance between the retinoscopist's
eye and the patient's (W.D).
• Which lenses she may be holding between
the patient's eye and her own.

CONTROLLING THE PROPERTIES OF
THE RETINOSCOPE
• Optical effects of moving the retinoscope
bulb to change the filament to lens distance;
this type of retinoscope emits convergent
light when the sleeve is moved up. Note the
vergences of the emerging rays:
• (left) concave mirror effect is produced
when bulb is moved down;
• (right) plane mirror effect is produced when
bulb is moved up.

THE RETINOSCOPE
Plane mirrorConcave mirror
Movement of the light source

RETINOSCOPE
However, two properties over which the
retinoscopist has total control are completely
intrinsic to the retinoscope she is holding.
• 1-The first is the orientation of the streak as
it leaves the retinoscope. Because the light
source for the retinoscope is a fine filament,
the light emanates from the retinoscope as a
fine streak.

RETINOSCOPE
• By rotating the light source, the
retinoscopist can easily alter the
orientation of the streak by more than
360 degrees. Merely by rotating the
sleeve on the handle of the retinoscope,
she can project a streak whose
orientation is parallel to the floor, or
perpendicular to it, or any meridian in
between.

RETINOSCOPE
• 2-The second property that can be controlled
easily by the retinoscopist is the vergence of
the incident streak. With the touch of a finger
(or thumb), the retinoscopist can alter the
streak so that it leaves the retinoscope as
converging, diverging, or even parallel light.
This feature gives the retinoscopist an
incredible ‫يصدق‬ ‫ل‬ amount of power in evaluating
a patient's refractive state. Unfortunately, it is
probably the most underused feature of the
retinoscope.

RETINOSCOPE
• Changing the distance between the light
filament and the condensing lens alters the
vergence of the emitted streak. This can be
accomplished by raising or lowering the
sleeve in the handle of the retinoscope.
• This is the most fundamental way in which
different models of retinoscope will contrast,
‫يتغاير‬‫التختل ف‬ and it is obviously important for
the retinoscopist to be familiar with the type
of retinoscope with which she is working.

RETINOSCOPE
• The condensing lens is fixed, and the light
source can be raised or lowered by moving
the sleeve up or down (Fig. 2).
• When the sleeve is raised in these
retinoscopes, the streak emanates as a
diverging beam; when the sleeve is lowered,
the streak emanates in a converging nature ,
and therefore we use the term “sleeve up”
when the retinoscope emits diverging light
and “sleeve down” when it emits converging
light.

RETINOSCOPE
By altering the vergence of the emitted streak, the
retinoscopist is actually manipulating its focal
point, the point where the emitted light comes
to focus in a point in real or virtual space.
When in maximum convergence (sleeve up), that
focal point is a real image located 33 cm in front
of the retinoscope. (You can test this by moving
the palm of your hand in front of the
retinoscope at a distance of 33 cm, then turning
it on with the sleeve raised all the way up.

Figure 2
concave mirrorplane mirror
Movement of the lens

THE RETINOSCOPE
• Optical effects of moving the lens to
change the filament to lens distance;
this type of retinoscope emits
convergent light when the sleeve is
moved up. Note the vergences of the
emerging rays: (left) plane mirror effect
when lens is moved down; (right)
concave mirror effect when lens is
moved up. 2

DETERMINING THE VERGENCE OF THE
RETINOSCOPE BEAM Lecture 1
To determine the vergence of a retinoscope
at any sleeve adjustment, a simple trick
called Foucault's Method (Fig. 4) can be
used. The most instructive‫ي‬ّ ‫ف‬ِ‫ي‬‫قي‬ِ‫ي‬‫ث‬ْ‫ِق‬‫ت‬َ part of
this exercise is shown in Figure 4A.
Note that when a card is introduced at the
edge of a converging beam, an opposite
movement is produced on a screen
located beyond the focal point.

Figure 4
against” motion
with” motion
with” motion
Screen
Rays converging beyond screen
Diverging rays
Rays converging at a focal point before screen

Foucault's method for determining vergence of
rays emerging from a retinoscope
• A card or your hand is introduced close to
the retinoscope and moved at right angles to
the emerging rays. Observe the shadow
produced in the unfocused image on a
screen or wall in a darkened room.
• (A) Rays converging at a focal point before
screen cause an “against” motion.
• (B) Rays converging beyond screen cause a
“with” motion.
• (C) Diverging rays cause a “with” motion.

• Foucault's method for determining vergence
of rays emerging from a retinoscope. A card
or your hand is introduced close to the
retinoscope and moved at right angles to the
emerging rays.
• Observe the shadow produced in the
unfocused image on a screen or wall in a
darkened room.
• A. Rays converging at a focal point before
screen cause an “against” motion.
• B. Rays converging beyond screen cause a
“with” motion.
• C. Diverging rays cause a “with” motion.

Calibration of the Converging
Beam
Bring the sleeve all the way up and place it
against a reflecting surface such as the wall.
Move away from the wall and observe from
the side (not through the peephole) until the
streak is in sharp focus on the wall. You
should note that when the retinoscope is
moved beyond that distance, the streak will
go out of focus because the filament light
has converged and then diverged (seeFig. 4
A).

• Return to the point of sharp focus and
measure to determine the focal point of
the retinoscope: it should be about 33
cm, which corresponds to + 3.00 D.
• Sit in the patient's examination chair
and aim the retinoscope toward the
distant wall while moving the sleeve up
and down.

Calibration of the Parallel Beam
• Watch where the finest focused image of
the filament is observed. Note the
relative position of the bottom of the
sleeve with regard to the range of sleeve
movement.
• In that position, the retinoscope beam is
as parallel as possible and it has no
vergence and thus is focused at infinity.

NEUTRALIZATION
RETINOSCOPY
Neutralization is performed with the retinoscope
held at a constant predetermined distance
from the patient with the sleeve all the way
down (light emitted in a diverging manner).
The retinoscopist makes decisions about the
patient's refractive error based on the
appearance of the retinoscope reflex after it is
reflected off the patient's fundus and back
through the pupil(Fig. 16).

NEUTRALIZATION
RETINOSCOPY
• What the retinoscopist sees is not the
image “on the retina” ,but rather the
magnified image “of the retina.”
• Therefore, discussion about
neutralization must begin with
discussion about the retinoscopic
reflex at neutralization.

THE NEUTRALIZATION REFLEX
• When performing neutralization the
retinoscopist shines diverging light
through the patient's pupil from a
standard working distance (usually 66
cm).
• This light is reflected off the patient's
fundus, and in this way, the fundus
acts as a new point source of light.
This is called the illuminating system.

• The light that originates from the luminous
retina then passes through the patient's
vitreous, lens, pupil, aqueous, and cornea,
until it finally exits the patient's eye on its
way back to the retinoscope. This is called
the viewing system.
• The retinoscopist must be able to
differentiate between the illuminating and
viewing systems because different
techniques of retinoscopy can depend on
varying the components of one but not the
other.

• 1-When diverging light is shone onto an
emmetrope's retina, the retina becomes
luminous and acts as a point source of light.
The rays of light then escape his eye in a
parallel fashion. If this concept is not
intuitive, ‫ي‬ّ ‫ديه‬َ‫ب‬َ merely follow the standard
light ray diagram backward.
• 2-In similar fashion, light starting as a point
on a myope's luminous retina is emitted as
converging light, where more myopic
individuals emit more highly converging light
than less myopic ones.

• 3-Similarly, light starting as a point on a
hyperope's luminous retina is emitted as
diverging light, and hyperopic patients emit
more diverging light than less hyperopic
ones.
• The vergence of the rays emitted from the
eye determines the qualities of the reflex
seen by the retinoscopist.
• A neutralization reflex occurs under the
circumstance when the far point of the eye
correlates ‫نظامية‬ ‫بصورة‬ ‫يربط‬ with the location
of the peephole of the retinoscope

• If a retinoscopist were to examine an
emmetropic eye at infinity, she could make
assumptions ‫افتراض‬ on the diverging,
converging, or parallel nature of the reflected
light by sweeping the retinoscope streak
back and forth across the patient's pupil.
• However, it is not possible to perform
retinoscopy from an infinite distance; it is
customary to adapt a working distance of 66
cm, corresponding to + 1.50 D.
• By introducing + 1.5 lens in front of the
subject's eye, the far point of a plano
prescription is relocated to 66 cm.

• In this circumstance, what the retinoscopist
is truly evaluating is whether the
:-retinoscope lies between the patient's eye
and far point, lies at the far point, or lies
beyond it.
1. If the patient is an emmetrope, the far point
lies on the horizon, and therefore the
retinoscope always must lie between the
patient's eye and far point.
2. If the patient is a hyperope, the far point
actually lies beyond the horizon, and the
retinoscope also lies between the patient's
eye and far point.
FP
FP

3-Things are more interesting, however, when
evaluating myopes in this way.
Light is emitted from a myope in a converging
manner so that the far point is somewhere in
real space (finite) in front of the myope's eye.
It is possible for the retinoscope to be placed
A- between the patient and far point,
B-exactly on the far point, or
C-out beyond the far point.

This relationship depends, of course, on
both the location of the retinoscope
(W.D), and the level of myopia (which
determines the location of the far
point).
C

• If the retinoscope is placed between the eye
and far point (as it is for all emmetropes and
hyperopes, and some myopes) and turned so
that the emitted streak is swept from side to
side across the patient's pupil, the light
reflex seen inside the pupil appears to sweep
in the same direction as the light emitted
from the retinoscope (seen on the patient's
iris, lids, brow, and cheek).
• This motion is called “with” motion because
the light that is afferent to the retinoscope
seems to move “with” the light that is
efferent from the retinoscope

• Fig. 17. The optical basis for neutralization <
retinoscopy>. The location of far points
produces the “with” and “against” motions
for a retinoscope with a divergent beam
when performing neutralization retinoscopy.
“With” motion is seen under all
circumstances except when the far point of
the eye-corrective lens system is situated
between the cornea and the peephole ‫ثقب‬ of
the retinoscope. The far point of the
illustrated eye is at the peephole and is thus
neutralized.

Lecture 2
With” motion reflex in
hyperopia

Fig. 18. “With” motion reflex in
hyperopia
A “with motion” reflex of light comes into the
shadow projected in the optical system from
the aperture of the retinoscope or the
examiner's pupil.
The rays from the filament to the retina are not
shown. They form an unfocused horizontal
filament image on the retina of the patient
that acts as a new object with its image
behind the retina.
When the retinoscope is tilted slightly, the
object (RETINA) moves down and the image
(REFLEX) moves down and vise versa. This
is seen as a “with motion” reflex.

Figure 19 against motion reflex of
myopia
• If the retinoscope is placed beyond the patient's far
point and swept from side to side across the pupil,
the light reflex (efferent) seen inside the pupil
appears to sweep in the opposite direction as the
streak emitted from the retinoscope (afferent )
Fig. 19
• This motion is called “against” motion because
the light emitted from the eye (efferent) appears to
move “against” the light that is emitted directly
from the retinoscope (afferent (.

Fig. 19. Origin of the “against”
movement in myopia

“On-off” phenomenon
• When the retinoscope is placed exactly on the
patient's far point, neither “with” nor “against”
motion is seen. At this point, all the light emitted
from the patient's eye enters the retinoscopist's
eye simultaneously.
• At exact neutrality, in a spherical eye with a small
pupil, the retinoscopist may see no motion at all;
rather, the patient's pupil seems to suddenly fill
with light as the streak moves across it.
• This is obtained in myopic eye exactly reciprocal
to W.D in diopters.
• This “on-off” phenomenon is important to
recognize because it serves as the end point
when performing the technique of neutralization.

Other qualities of the reflex
• In addition to its direction of movement, other
qualities of the reflected retinoscope streak
can be evaluated. These qualities all give the
retinoscopist clues as to how close to the far
point the retinoscope is being held.
The three most important qualities of the reflex
are:
1. the speed at which it moves,
2. its brightness,
3. its width.

If one thinks of the reflex at the
neutralization point as :
• infinitely fast (so fast that it immediately
fills the pupil without apparent motion),
• infinitely ‫ ه‬ُ b ‫ل‬َ‫ّلِح‬ ‫د‬َّ ‫ح‬َ‫ّلِح‬ ‫ل‬ ; ‫ددود‬ُ b‫ح‬ْ‫ُد‬ ‫م‬َ‫ّلِح‬ ‫ر‬ُ b ‫ي‬ْ‫ُد‬‫غ‬َ‫ّلِح‬ bright, and
• infinitely wide, it is easy to understand
what the reflex should look like when the
retinoscope is either near to, or far from,
the neutralization point Fig. 20

qualities of the reflex
• When the retinoscope is held near the patient's
far point, the reflex should appear fairly fast,
bright, and wide.
• As the retinoscope is moved farther from the far
point, the reflex appears to move slower and is
dimmer and thinner.
• The retinoscope can eventually be moved so far
from the patient's far point that the reflex is slow,
wide, and dim enough that it is quite difficult to
recognize as a reflex at all.

• Fig. 20 .Neutralization retinoscopy diagram of
changes in characteristics of reflex as in the
zone surrounding the point of neutrality.
• At neutrality, the reflex motion may be so fast
that it cannot be detected. The end point or
end zone should be approached from the
“with” reflex side and the judgment of
neutrality made erring ‫زل‬ِ‫ي‬ ‫ي‬َ . ‫يخطئ‬
toward the “with” reflex rather than the
“against” reflex.
• The neutral point lies within the
neutralization zone where neutralization is
best observed. (

Optics of the Neutralization
Reflex
• Five features characterize the neutralization end
point, the point at which neither a “with” nor
“against” reflex can be identified. Three of these
are considered to define the end point, but two
others can also be observed. The three standard
characteristics are :
• Increases in speed, brightness, and width of
the moving image. )1,2 3 )
• To these can be added : the “on-off phenomenon”
(the intermittent disappearance of the observed
reflex) and the scissors reflex) .4 5 (

Reflex
1-Speed of the “with” or “against” motion:
• If the retinoscope mirror is tilted in a highly
ametropic eye, the resultant reflex is (more rapid )
imaged at a far point that is much closer to the
eye than the reflex of an almost emmetropic eye,
the far point of which is located at a much greater
distance.
• With regard to the subject's pupil, movement of
the image at the far point of the almost
emmetropic eye will seem to have a greater
angular velocity or speed.

Reflex
• It should be stressed that the direction of
movement of the fundus image is not influenced
by the patient's ametropia ( illuminating system).
• The “with” or “against” movement is a function of
the observation (VIEWING) system, thus an
“against” movement occurs only when the eye
and external lens system have a far point lying
between the patient's eye and the retinoscope
peephole )High myopia)

Reflex
2-Brightness of the image:
• As neutrality is approached, all of the rays
emerging from the patient’s eye are focused at
the peephole, where they provide the brightest
image that the examiner observes. Illumination
increases inversely to the square of image size.
• At any other focal distance, some or all of the
rays of light will not reach the peephole and the
image becomes duller Fig. 21

3-Width of reflex
• In general, the width of the streak reflex and the
apparent speed of the streak reflex as it moves
across the pupil give an indication of how far you
are from neutrality.
• Young eyes that are not diseased and have not had
surgery give the most defined reflexes. Corneal
diseases, cataracts, IOLs, hazy posterior capsules,
and cloudiness in the vitreous distort the reflexes
and change the rules of appearance.
• Sometimes width and speed do not give reliable
clues and you must just rely on apparent with-
motion to arrive at the best retinoscopic estimate.

A very wide (almost filling the pupil), slow
moving streak reflex indicates that you are a long
way from neutrality. For instance, the with or
against reflex you would see at plano when
streaking a (– or +5.00 hyperope.(

As we add plus sphere power the
streak tends to narrow and speed up
in its apparent motion.
3-Width of reflex

As we continue adding plus sphere
power and approach‫تقريبا‬ neutrality, the
streak widens again and speeds up even
more.
3-Width of reflex

At neutrality the streak reflex
widens more to completely fill the
pupil.
3-Width of reflex

3-Width of reflex
In astigmatism :Streaking one meridian gives
you against- motion, and streaking the
meridian 90 degrees away gives you with-
motion.
• Streaking one meridian gives you with-
motion (or against- motion) with a wide
streak reflex, and streaking the meridian 90
degrees away gives you the same motion
but with a narrower streak reflex.

3-Width of reflex
a wide streak reflex,narrower streak reflex

3-Width of reflex
• As we add plus sphere power, the
reflex at 90 narrows and the reflex at
180 quickly widens and reaches
neutrality.

Reflex
4-The on-off phenomenon: Although the
retinoscopic reflex is bright and wide on
either side of neutrality, the reflex may
disappear completely when the retinoscope
peephole is exactly conjugate to the eye-
corrective lens system i.e far point of the
examined eye. (see Fig. 21 (.
• Fortunately, neither the patient's eye nor the
examiner's eye and hand can maintain this
exact position for long, but astute ‫ذكي‬
retinoscopist may notice the on-off
phenomenon at neutrality.

Reflex
• Fig. 21. The origin of the on-off
phenomenon at neutrality. The far point of
the eye is situated at the peephole of the
retinoscope. Either all or none of the rays
will pass through the peephole with the
slightest shift in the subject's eye or the
retinoscope or the retinoscopist's eye,
causing the retinoscopist to see the
contents of the pupil as either filled with
light or black.

Fig. 21 the on-off phenomenon at
neutrality
Patient’s eye

Reflex Lecture 3
5-The scissors reflex: The refractive elements of
the eye are not perfectly spherical. Thus, the
center of the optical path may be slightly myopic
when compared with that of the periphery.
The amount of aberration may be small, but under
circumstances of perfect neutralization and a
widely dilated pupil, the center of the optical path
may return a “with” motion while the periphery
returns an “against” motion.

Reflex
• This pattern of opposing central and
peripheral retinoscopic movements is
known as a scissors reflex. There is only a
small dioptric distance over which the
scissors reflex can be detected. The entire
reflex returns to all “with” or all “against”
motion within about 0.50 D on either side
of neutralization). narrow zone)

Estimating Low Myopes via
Neutralization Without Lenses
• By now the reader should have determined that
it is in fact quite possible to neutralize low
myopes without the use of lenses.
• The trick is to place the retinoscope directly on
the patient's far point, sweep the retinoscope
streak across the patient's pupil with the sleeve
down, recognize the “on-off” phenomenon of the
neutralization reflex, measure the distance from
the patient's eye to the retinoscope in meters,
take the reciprocal—thus converting from meters
(distance) to diopters (vergence)—and the
patient's refractive error has been determined.

Neutralization Without Lenses
• For example, neutralization for a -2.00-D myope
can be seen by placing the retinoscope 50 cm
from the patient's eye, and for a -4.00-D myope
by placing the retinoscope 25 cm from this
patient's eye (without considering a certain W.D(
• Neutralization for an emmetrope can only be
done in this fashion by placing the retinoscope
infinitely far from the patient's eye—theoretically
possible, but not practically feasible. ‫ملمئم‬ . ‫ي‬ّ ‫م‬ ‫عمل‬

NEUTRALIZATION Without Lenses
• Because the far points of hyperopes do not lie in
real space (they lie beyond infinity), hyperopes
cannot be neutralized in this way.
• The aforementioned technique describes a way
to estimate a low myope's refractive error
without the use of lenses.
• The key to this method is that the retinoscopist
must change the distance that the retinoscope is
held from the patient's eye when trying to find
the far point.

Performing neutralization
• When performing neutralization she does exactly
the opposite—she holds the retinoscope at a
constant specific working distance and uses
lenses to bring the patient's far point to the
retinoscope.
• The first thing that a retinoscopist must do is
choose a comfortable working distance. She
wants to be as far from her patient as possible
while still being close enough to comfortably
manipulate lenses in front of his eye. Thus, the
working distance usually is described as “arms
length” away from the patient.

Performing neutralization
• For the average retinoscopist, this distance
works out to about 66 cm. Taller retinoscopists
may prefer 75 cm, whereas shorter ones may
use 50 cm.
• It is not uncommon for retinoscopists to work
closer than their usual working distance in
difficult cases, such as small children, or adults
with cataracts or small pupils.
• The actual working distance does not matter as
long the retinoscopist is aware of the distance
and adjusts her calculations accordingly.

Performing neutralization of
against” motion
• The retinoscopist should be able to sit at her
comfortable working distance while using lenses
to bring the patient's far point to her.
• The retinoscopist accomplishes this feat‫ل‬ٌ ‫عم‬ . ‫ل‬ٌ ‫عم‬
‫ذ‬ّ ‫م‬‫ف‬َ‫ّلِح‬ by sweeping the retinoscope streak across the
patient's pupil and evaluating the direction,
speed, brightness, and width of the reflex.
• If she observes “against” motion, the
retinoscope must lie beyond the patient's far
point, and the retinoscopist can move the far
point toward the retinoscope by placing a minus
lens in front of her patient's eye.

against” motion

against” motion
• If the reflex is fast, bright, and wide, the
retinoscope must have been near to the patient's
far point, and a weak minus lens should be
chosen.
• However, if the reflex is slow, dim, and narrow, the
retinoscope probably lies a greater distance from
the far point, and a stronger minus lens should be
chosen.
• If “with” motion is observed after a minus lens is
placed before the patient's eye, the patient's far
point has been moved beyond the retinoscope
because too strong of a minus lens was chosen.
This lens should be removed and replaced with a
weaker minus one.

Performing neutralization of “with”
motion
• Similar manipulations are performed if “with”
motion is initially seen when neutralization is
begun. In such cases, the far point must lie
beyond the retinoscopist's comfortable
working distance.
• Again, how far away the far point lies can be
estimated by judging the quality of the reflex.
• A plus lens then is chosen to bring the far
point forward toward the retinoscope.

Performing neutralization of “with”
motion
• Whenever possible, the retinoscopist should try
to manipulate the far point in such a way that
“with” motion is being observed.
• A “with” reflex typically is sharper and easier to
judge than an “against” reflex. Thus, if
“against” motion is seen, neutralization will be
easier to perform if a strong enough minus lens
is placed to push the far point beyond the
retinoscope, so that the retinoscopist can
observe “with” motion.

minus lenses in front of younger
patients can excite accommodation
• Care must always be taken, however, when
putting minus lenses in front of younger
patients because they can easily “eat up”
this minus by accommodating, thus leading
the less careful retinoscopist down the
wrong path.
• It should also be noted that the
neutralization end point is not exactly an
end point—rather it is an end zone that
measures about half a diopter in depth (see
Fig. 20(

“zone of doubt” varies with pupil
size and working distance
• The true size of this “zone of doubt” varies with
pupil size and working distance —it is narrowest
with a small pupil and close working distance.
• Best results are achieved when entering the
zone of doubt from the plus side, by watching
the “with” motion reflex get faster, brighter, and
wider until the retinoscopist is convinced the
neutralization reflex has been achieved.
• If the zone of doubt is entered from the minus
side (through “against” motion), there is a
greater chance for error.

The neutralization reflex
• Eventually, after just a few different lenses
are placed before the patient's eye, the
retinoscopist can observe the neutralization
reflex.
• At this point the goal is achieved, and the
retinoscopist has managed to bring the
patient's far point to the retinoscope (which
is being held at the working distance).
• The retinoscopist is now ready to write a
spectacle correction )‫؛‬ prescription(.

CORRECTING THE PRESCRIPTION FOR THE
WORKING DISTANCE LENS
• However, the lenses currently in front of
the patient's eye do not represent the
correction needed to see clearly at infinite
distance; rather, the lenses represent the
correction needed to see clearly at 66 cm.
• The patient will be quite dissatisfied ‫غير‬
‫ض‬ٍ ‫را‬ if given a prescription for a pair of
glasses that allows for clear vision only 66
cm away or closer.

• The retinoscopist must always remember
to modify the prescription for distance
vision, a mathematical manipulation called
correcting for the working distance.
• The gross power is that which the
retinoscopist is holding when retinoscopy
is completed.
• This corresponds to the power that brings
light from the patient's luminous retina to
focus at the working distanceِ‫ّل‬( on the
peephole of the retinoscope(.

• The net power is that which neutralizes
the patient's refractive error for good
distance vision—the power that focuses
light from the luminous retina of the patient
to a point at the horizon. )His far point
must be at infinity after full correction).

CORRECTING THE PRESCRIPTION FOR
THE WORKING DISTANCE LENS
• The mathematical computation ‫سباب‬َ‫ّلِح‬ ‫ت‬ِ‫ّل‬‫ح‬ْ‫ُد‬ ‫ا‬ِ‫ّل‬ ; ‫حصباء‬ْ‫ُد‬ ‫إ‬ِ‫ّل‬ is
simple. The retinoscopist merely subtracts the
working distance (in diopters) from the gross to get
the net power.
• For example, when the working distance is 66 cm
1.50 +)= D) and the patient is neutralized with a
• -2.5 D. lens, the gross power minus the working
distance equals the net power,
or: -2.5 - (+ 1.5) = - 4D.
• The retinoscopist will give a prescription for a - 4D.
lens. The previous discussion describes
neutralization of spherical patients.

NEUTRALIZATION OF ASTIGMATIC EYES
• In patients with astigmatism, the reflex seen
in the pupil has one more quality in addition
to speed, brightness, and width. The reflex in
patients with astigmatism also appears to
“break” as the light filament is rotated Fig.
22. The retinoscope reflex seen in the
patient's pupil will not be continuous with the
streak lying on the cornea, lids, forehead,
and cheek; it will appear broken.
• There will be, however, two meridians where
the retinoscope reflex will be continuous with
the streak—where it will not appear broken.

• These meridians correspond to the two axes of
the patient's astigmatism. The retinoscopist
merely needs to neutralize these two meridians
separately and combine them to come up with the
desired spectacle correction
• This can be done using only spherical lenses (as
is best when neutralizing children with loose
lenses), spherical and plus cylindrical lenses
(using a plus cylinder phoropter or loose lenses
and trial frames), or spherical and minus
cylindrical lenses (using a minus cylinder
phoropter or loose lenses and trial frames).

• Let us further explore the methods of
neutralizing astigmatic individuals in whom
the less plus (or more minus) axis is
neutralized first and the more plus (or less
minus) axis is neutralized second.
• When neutralizing the axes in this order,
the retinoscopist can use either only
spherical lenses, or spherical and plus
cylindrical lenses.

Fig. 22.phenomenon Break
The line between the streak in the pupil
and outside the pupil is broken when
the streak is off the correct axis. (

BREAK PHENOMENON
• Astigmatism can also be detected by
observation of the break phenomenon.
It is useful in refining the axis of large
astigmatic cylinders because one can
observe a discontinuity, or “break,”
between the enhanced intercept axis
and that of the retinal reflex when the
retinoscope filament beam is rotated
somewhat away from the correct
cylinder axis (see Fig. 22).

• Procedure for neutralizing an astigmatic eye
• 1. The first step is to neutralize one of the meridians.
You will be adding plus sphere power and streaking each
of the primary meridians after each power change.
• The meridian with the narrow, fast reflex will neutralize
first. This meridian will be 90 degrees away from the
meridian with the widest, slowest streak reflex.
• In this example, the 180 degree( right one ) meridian will
neutralize first.

As we add plus sphere power, the reflex at
90(left ) narrows and the reflex at 180 (right )
quickly widens and reaches neutral point.
Procedure for neutralizing an astigmatic eye

• 2. The next step is to confirm/identify the axis of
the astigmatism. We have a good idea of what the
axis is from the neutralization process. There are
several clues that we can use:
A. The Thickness Phenomenon
B. The Intensity Phenomenon
C. The Break and Skew Phenomena
D. Straddling the Axis

The Thickness Phenomenon:
The streak reflex appears to be narrowest ( left ) when
we are streaking the meridian of the correct axis.
As you move away from the correct axis, the streak
reflex becomes wider ( right ).

Procedure for neutralizing of an astigmatic
eye
• The Intensity Phenomenon
The streak reflex appears brightest
when you are streaking the
meridian of the correct axis.
As you move away from the correct
axis, the streak reflex becomes
more dim (less bright ).

The skew phenomenon:
If we streak a meridian that is away from the
meridian of the correct axis, the reflex will
tend to travel along the correct meridian
rather than follow the streak. This guides us
back to the correct meridian.
The skew phenomenonThe skew phenomenon
Correct axis
Procedure for neutralizing an astigmatic
eye

• Straddling the Axis
Assuming that there is regular astigmatism present,
when one meridian has been neutralized, the meridian
exactly 90 degrees away will have the strongest, most
defined with- motion reflex.

•
The axis can be confirmed by streaking
the meridians 45 degrees to each side
of what we believe to be the meridian of
the correct axis.
In this case we believe that streaking the
90 degree meridian gives the most
defined reflex.
We streak the 45 degree meridian and the
streak reflex widens and degrades in
sharpness.
The same thing happens when we streak
the 135 degree meridian. This confirms
90 degrees as the correct meridian.
45 degrees
135 degrees
Straddling the Axis
eye

STRADDLING
When the cylinder power is weak, straddling
reveals an initial incorrect estimate of the axis
location.
The thinner image is called the “guide” because
it guides us to adjust the plus-cylinder axis
toward the thinner image.
This step provides the initial detection of
astigmatism, and the phoropter axis can be
adjusted so that plus lenses can be dialed into
place along the enhanced meridian.

Straddling
• The straddling meridians are 45 degrees off
the glass axis, at roughly 35 and 125
degrees. As you move back from the eye
while comparing meridians, the reflex at 125
degrees remains narrow (A) at the same
distance that the reflex at 35 degrees has
become wide (B). This dissimilarity indicates
axis error; the narrow reflex (A) is the guide
toward which we must turn the glass axis.

eye
• If the reflex in one of the straddle
meridians is narrower than the reflex in
the other straddle meridian, then we
would adjust our estimated axis in the
direction of the straddle meridian with
the narrower reflex (guide).
• We would retest 45 degrees to each
side of the new axis to confirm that the
reflex in each straddle meridian is
equally wide.

Spherical Lens Technique
• The first step is for the retinoscopist to find
the least plus axis. The retinoscope streak is
swept back and forth across the pupil while it
is rotated 360 degrees by rotating the light
filament in the handle.
• The retinoscopist then observes at which
two meridians the retinoscope reflex does
not appear broken—in cases of regular
astigmatism, these two meridians should be
90 degrees apart.

• The retinoscopist then compares the reflex in one
meridian to the reflex in the other, noting which
meridian's streak exhibits more “against” (slower,,
broader , dimmer) or less “with” (faster, thinner,
brighter) qualities than the other.
• The second meridian is neutralized first. If the
reflex in one meridian shows “with” motion and in
the other shows “against” motion, the meridian
with the reflex that shows “with” is neutralized
first

• The more minus meridian of the astigmatic person
is then merely neutralized (second ) much as the
spherical myope or hyperope described
previously.
• The axis of the streak is held along the meridian
line and swept in a direction perpendicular to it i.e
(if the 90-degree axis is being neutralized, the
streak is oriented straight up and down and swept
from side to side) perpendicular to 90 degrees.

• At first, it is not intuitive that the streak be held in
the same orientation as the axis meridian
because one is searching for the power of the
astigmatism, and the power lies not along the
axis, but perpendicular to it.
• Here the retinoscopist must remember that the
power is found not by holding the streak still
(fixed ) , but rather by sweeping (moving ) it
across the pupil.
• The retinoscope streak is rotated 90 degrees,
and the reflex is re-examined.

• The reflex should not appear broken in the
new meridian—a broken reflex signifies that
either the retinoscope streak is not exactly
aligned along the patient's second axis or that
the patient has irregular astigmatism.
• If the reflex is not broken, it is neutralized
with spherical lenses. If spherical lenses are to
be used, the second meridian is neutralized in
exactly the same manner as the first after
removal of the lenses used before and starting
a new steps to neutralize the other meridian
also with spherical lenses .

• Once the neutralization reflex has been
found in the second meridian, the
retinoscopist again subtracts the
working distance from the power in the
2 meridians and records the lens power
needed to correct the patient for each
particular axis. The difference in power
of lenses between the 2 meridians is
considered astigmatism.

• A simple conversion then needs to be performed before
presenting the patient with the proper spectacle
prescription, as follows:
• Q: A patient is neutralized with the following lenses at a
working distance of 66 cm: [+ 3.50 axis 90] and
[+ 4.25 axis 180]. What is the eyeglasses prescription?
A: Step 1: Subtract the working distance. In this case,
the working distance is 66 cm, which is equal to 1.50 D:
[+ 3.50 axis 90] - 1.50 = + 2.00 axis 90
[+ 4.25 axis 180] - 1.50 = + 2.75 axis 180
Step 2: Transpose from cross-cylinder notation to plus-
cylinder notation:
+ 2.00 sphere + ([+ 2.75 - 2.00] axis 180)
Objective prescription = +2.0 DS+ 0.75 DC x 180

Plus-Cylinder Technique
• If the second meridian is to be neutralized
with a plus-cylinder lens (as is done with a
plus-cylinder phoropter or loose lenses
and trial frames), the first spherical lens
should be left in the phoropter or trial
frames.Keeping the spherical lenses in
place. The axis of the cylindrical lens is
oriented in the direction of the axis of the
streak for the second meridian.

• Because a cylinder lens is being used, no
power is being added along the axis of the
second meridian (which, of course,
corresponds to the power of the first
meridian).
• When the neutralization reflex is found for
the second meridian, the streak is rotated
90 degrees to ensure that the first
meridian is still neutralized.

• The working distance is then subtracted from the
spherical lens only, and the spectacle prescription is
easily determined as follows:
• Q: A patient is neutralized with the following lenses
at a working distance of 66 cm: [+ 3.50 sphere] and
[+ 0.75 axis 180]. What is the eyeglasses prescription?
• A: Step 1: Subtract the working distance from the
spherical lens only. In this case, the working distance
is 66 cm, which is equal to 1.50 D:
[+ 3.50 sphere] - 1.50 = + 2.00 sphere
Step 2: Add the cylindrical lens to the new power of
the spherical lens:
+ 2.00 sphere + [+ 0.75 axis 180]
Objective prescription= 2.00 + DS + 0.75 DC x180

Minus-Cylinder Technique
• Some clinicians prefer to work in minus cylinder,
patients are neutralized in the same aforementioned
manner, except that the more “with” or less
“against” meridian is neutralized first with spherical
lenses.
• Then the less “with” or more “against” meridian is
neutralized with a minus-cylinder in much the same
way as the previous example used a plus-cylinder
lens.
• The transposition is done as follows:

Minus-Cylinder Technique
• Q: A patient is neutralized with the following
lenses at a working distance of 66 cm: [+ 4.25
sphere] and [-0.75 axis 90]. What is the
eyeglasses prescription?
A: Step 1: Subtract the working distance from
the spherical lens only. In this case, the working
distance is 66 cm, which is equal to 1.50 D:
)+ 4.25 -1.50 (= + 2.75 sphere
Step 2: Add the minus cylindrical lens to the
new power of the spherical lens:
• + 2.75 sphere + (-0.75 axis 90(
90 × 0.75 - 2.75 + =

The next step is to neutralize the astigmatism
(with minus-cylinder power).
Remember that one meridian has already been
neutralized. The meridian 90 degrees away still
has with-motion. We begin by streaking this
meridian that has the brightest, narrowest with-
reflex.

Since we are using a minus-cylinder lens, we
will line up our cylinder axis perpendicular to
the orientation of the streak. In other words,
at 90 degrees in this example. We are
streaking the 90 degree meridian, and the
axis of the correcting minus-cylinder will be
90 degrees.

Once we have a neutral reflex, we have reached the
endpoint. Neutrality can be assumed when any with-
motion just disappears. This is preferable to relying
on recognizing a neutral reflex, because the reflex
may appear neutral over a wide range of power
settings.

The final step is to subtract for our
working distance. Lecture 6
• This is usually 1.50 D and it is subtracted from the
sphere power only. Suppose our phoropter reads
• -1.00-150x90 when we have finished neutralizing the
astigmatic meridian.
• We then would subtract 1.50 D sphere power for a
final retinoscopic estimate of -2.50-1.50x90.
• It is easiest to practice retinoscopy on younger
adults, ages 20 to 50. They usually have clear
media, relatively relaxed accommodation, and a
definite refractometric endpoint with which to
compare your retinoscopy.

RELIABILITY‫ية‬ّ‫ة‬‫الموثوق‬
Because important therapeutic judgments may
depend on the retinoscopic measurements, it
is necessary to know how reliable these
measurements are. Reliability and precision
‫إحكام‬ . ‫ضبط‬ . ‫قة‬ّ‫ة‬‫د‬are terms that describe the
degree to which repeated measurements
resemble one another. For example, five
repeated measurements for one patient
might yield the following five spherical
results: + 2.25, + 2.75, + 2.50, + 2.75, + 2.25.

• With another examiner, the following values
might be found: + 1.75, + 2.50, + 3.25, + 2.75,
+ 2.25. The first examiner displays‫ز‬َ a ‫ر‬َ a ‫ب‬ْ‫َر‬‫أ‬َ a ; ‫د ى‬َ a‫ب‬ْ‫َر‬‫أ‬َ a a
higher degree of reliability or precision than
the second one. Nevertheless, the average
value is the same for both: + 2.50.
• If any single measurements had been
accepted as the patient's true refractive
error, the patient might have been misjudged
by only ¼D by the first examiner, but by as
much as ¾D by the second.

• How is it possible, then, to judge the
reliability of any measurement? The answer
is straightforward: There must be repeated
measurements so that the variability of the
measurements can be assessed.
• The repeated measurements should be
independent of one another, each derived
without the measurer having knowledge of
what the preceding ones were.

• These are usually called “replicate ‫ثنى‬ ;‫طو ى‬
measurements,” and there is no way to judge
reliability without them. In clinical practice,
we often do these replicate measurements
informally and almost intuitively.
• Fluctuations in the measurement process are
unavoidable; statisticians call them “error.”
• The second examiner in the previous
example is less precise than the first. She
showed greater variability and larger error.

Reliability
• Reliability and error for retinoscopy have
been evaluated. One study by Safir and
coworkers entailed five clinicians performing
retinoscopy on ten healthy young subjects
on two separate occasions separated by one
to three weeks. Results showed a 50%
probability that the two measurements of
spherical power would differ by 0.40 D.
• The Safir study also showed a threefold
difference in reliability among retinoscopists.

Accuracy
• Accuracy is another concept that is
important in the understanding of
measurement.
• Accurate measurements are those that
are close to the “true” value being
measured. Accuracy is a relative
concept‫مفهوم‬
• One procedure may be more or less
accurate than another.

• Suppose, for example, that a subject's true
spherical refractive error were 2.00 D, and
that ophthalmologist A measured it five times
as 2.25, 2.25, 2.00, 2.00, 1.75, whereas
ophthalmologist B got values of 2.5, 2.5, 2.75,
2.75, and 3. It is apparent that the method of
ophthalmologist A is more accurate than that
of ophthalmologist B.
• The typical measurement for ophthalmologist
A is closer to the quantity sought than that of
ophthalmologist B, even though the
precision ‫ضبط‬ . ‫قة‬ّ‫ة‬‫د‬ of the two refractionists
is about the same. This example shows that
there is no predefined relationship between
precision and accuracy.

THE ROLE OF THE RETINOSCOPE IN A
MODERN EYE CLINIC-Autorefraction
• In the 21st century, we are faced with an
ever-more automated world, and the
ophthalmic practice has paralleled this move
toward automation. ‫اللى‬ ‫أو‬ ‫التوماتى‬ ‫التشغيل‬
• The retinoscope, really little more than a
light filament, lens, and mirror, is now joined
by many more sophisticated (and certainly
more expensive) devices developed to help
us obtain information regarding the refractive
state of our patients.

• One family of such instruments consists of
the automated refractors—tabletop or hand-
held devices that perform an objective
refraction in a matter of seconds at the touch
of a button.
• The largest advantage of the automated
refractor is that clinic personnel‫الموظفين‬ ‫مجموع‬
who have almost no knowledge in the art of
refraction can use it. For the average patient,
automated refractors are reasonably
accurate when compared with the
retinoscope and generally agree within ½ D.

• Autorefraction
• If automated refractors err‫يخطئ‬ , they tend to
overestimate minus sphere by a fraction of a
diopter. This discrepancy ‫ق ض‬ُ‫ض‬‫تنا‬ . ‫ر ض‬ُ‫ض‬ ‫تعا‬
probably stems from the fact that patients
accommodate in response to their sense that
the automated refractor is at a closer
distance to the patient than is the 6 meter far
point used in retinoscopy. This is true even
though the devices are designed to relax
accommodation while fixing on an artificial
distant target.

Autorefraction
• Where the automated refractor is at an undeniable ‫ال‬
‫حد‬َ a ‫ج‬ْ‫َر‬ ‫ي‬ُ‫ض‬ ‫ال‬ . ‫كر‬َ a ‫ن‬ْ‫َر‬‫ي‬ُ‫ض‬ disadvantage to the retinoscope is in
evaluating patients with irregular astigmatism, either
from pathology (e.g., keratoconus, pellucid marginal
degeneration) or postsurgically (e.g., corneal
transplant, laser in situ keratomileusis [LASIK]). All
the automated refractor operator can do is press a
button while having the patient fixate on the target.
• The automated refractor then either calculates a
“best fit” refraction or flashes an error message that
there too much irregular astigmatism exists to make
a reading.( Over cylinder)

Autorefraction
• The retinoscopist, however, can gain much more
information about the refractive state of the patient
by judging the quality of the light reflex observed in
the patient's pupil.
• A skilled retinoscopist usually can deduce
quantities and qualities of astigmatism in patients
for whom the automated refractor fails. This is
especially true in patients with poor best-corrected
visual acuity.
• Other instruments that must be compared with the
retinoscope are the keratoscope and the automated
corneal modeling systems. Although it is tempting to
compare these instruments with the retinoscope
because they each provide important information
regarding astigmatism,

Autorefraction
• it must be remembered that these
instruments serve different purposes within
the ophthalmic practice. The keratoscope
and corneal topographers are used to
evaluate corneal astigmatism only.
• The retinoscope, however, is used to
determine the entire refractive state of the
eye. These instruments all have their place
and can complement‫تكملة‬ each other well.

• A final issue, one that is becoming more
important with every passing year, is the role
of the retinoscope in managing the refractive
surgery patient. Few studies address this
problem. Retinoscopy has been shown to be
accurate in evaluating the postoperative
patient. Anecdotally, ‫هة‬َ a ‫كو‬ُ‫ض‬‫ف‬ْ‫َر‬‫أ‬ُ‫ض‬ ; ‫فة‬َ a‫رو‬ُ‫ض‬ ‫ط‬ْ‫َر‬ ‫أ‬ُ‫ض‬ we agree
with these results. In our practice, we rely
heavily on retinoscopy in evaluating pre- and
postoperative refractive surgery patients.

• We believe that automated refractors cannot
accurately evaluate the refractive state of
someone with a surgically altered cornea and
therefore believe that they have no role in
providing data on these patients.
• Other studies have shown that corneal
topography alone is not adequate in
evaluating patient satisfaction after laser
refractive surgery.

• Remembering that the critical zone of the
retinoscopy reflex is the central 3 mm, and
that the average excimer laser ablation
diameter is 6 mm, one can see that the
retinoscope is well suited to evaluate these
patients.
• When patients who had previously had
corneal refractive surgery subsequently
undergo cataract extraction with intraocular
lens (IOL) implantation, there is more
variability in the postoperative refractions
than for typical cataract patients.

The IOL calculations rely not on retinoscopy
(objective refraction), but instead on
keratometry (corneal curvature) and a-scan
ultrasonography (axial length). One can only
wonder if the diagnostic procedure of choice
for these patients might someday be for the
surgeon to remove the cataract, perform
intraoperative retinoscopy of the aphakic
eye, calculate the necessary lens power, then
place the desired IOL implant.

•In that way, the IOL would depend on
the patient's refractive state rather than
on artificial calculations based on the
patient's altered ocular anatomy.

Degrees of Astigmatism
Mild
Astigmatism
1.00
diopters
Moderate
Astigmatism
1.00to 2.00
diopters
Severe
Astigmatism
2.00to 3.00
diopters
Extreme
Astigmatism
3.00
diopters

Clinical classification of astigmatism
1. Regular astigmatism :in which the two principle
meridians are at right angle and is susceptible to
easy correction by cylindrical lenses.
2. Oblique astigmatism :in which the two principle
meridians are not at right angle but are crossed
obiquely,it is corrected by using
spherocylindrical lenses ,it is not very common.
3. Irregular astigmatism :where there are
irregularities in the curvature of the meridians so
that no geometrical figure is formed ,and the
correction is very difficult.

Types of astigmatism
1.Simple astigmatism :where one of
the foci falls upon the retina while
the other focus may fall in front or
behind the retina so that while one
meridian is emmetropic the other
meridian is either myopic or
hypermetropic .

2.Compound astigmatism :where neither
of the two foci lies upon the retina but
both are placed in front of or behind
the retina on the same direction ,the
state of refraction is then entirely
myopic (compound myopic
astigmatism) or entirely hypermetropic
(compound hypermetropic
astigmatism) .

3.Mixed astigmatism :where one focus is
in front of and the other is behind the
retina, so that the refraction is myopic
in one direction and hypermetropic in
the other.

Other classification
Direct astigmatism :when the
vertical curve is greater than the
horizontal curve.
Indirect astigmatism :when the
horizontal curve is greater than the
vertical curve.
B a c k

1.Patients with astigmatism have
blurred or distorted vision at all
distances.
2. It can also cause images to
appear doubled, particularly at
night.
3.Patients have difficult focusing
on various objects such as finely
printed words and lines.
4.Headache and fatigue of the
eye are common as the person
tends to strain his eyes.
5.Eye discomfort and irritation
are also frequent.
What are the general symptoms of
Astigmatism ?

Symptoms of low astigmatism
(1.0D) include
1. Asthenopia {tired eyes},
especially when doing precise ‫قيق‬ِ‫قي‬‫د‬َ a
work at a fixed distance.
2. Transient blurred vision relieved
by rubbing the eyes as in
hyperopia when doing precise
work at a fixed distance.
3. Frontal headaches with long
periods of visual concentration
on a task.

Symptoms of high astigmatism
(1.0D) include
1. Blurred vision , asthenopia and frontal headache
are more severe than in low astigmatism
2. Tilting of the head for oblique astigmatism
3. Slinting to achieve pinhole vision clarity.
4. Reading material held close to eyes to achieve
large (as in myopia) but blurred retinal image.
5. The letters in the book appear as running
together i.e. getting mixed up.

Optical condition in astigmatism

Causes of Astigmatism
Heriditary :
• The exact cause remains unknown; however some
common types of astigmatism seem to run in
families and may be inherited.
• It is thought that most people have some form of
astigmatism as it is rare to find perfectly shaped
curves in the cornea and lens, but the defect is
rarely serious.
• The majority of these studies demonstrate an
autosomal (of asexual chromosomes )dominant form
of genetic transmission. Autosomal recessive
transmission has been shown occasionally. Rarely,
X-linked recessive form has also been reported.

Acquired causes of astigmatism
1. Diseases of the cornea result in its deformity; an
extreme example is seen in conical cornea
(keratoconus), while inflammations and ulceration of
the cornea produce corneal scar.
2. Traumatic interference with the cornea may bring about
the same result in this category we should include
surgical trauma, particularly operations for cataract.
Furthermore, corneal astigmatism can be induced by
the pressure of swellings of the lids, whether the
humble chalazion or a true neoplasm.
3. A transient deviation form normal can be produced by
finger pressure on the eye, by contraction of the lids
(blepharospasm ), or by the action of the extra-ocular
muscles.

Acquired causes of astigmatism
4. Curvature astigmatism of the lens also
occurs with great frequency. In great
majority of cases such anomalies are small;
but on occasion, as in lenticonus, they may
be marked.
5. Not uncommonly the lens is placed slightly
obliquely or out of line in the optical system
and this, causing a certain amount of
decentring, produces a corresponding
astigmatism;
6. A traumatic subluxation of the lens has
similar results

Keratoconus (KC)
Keratoconus is a
progressive disorder in which
the cornea assumes an
irregular conical shape. The
onset is at around puberty with
slow progression thereafter.
Though the ectasia may
become stationary at any time,
both eyes are affected, if only
topographically, in almost all
cases.

Characteristics
INCIDENCE:
Keratoconus is bilateral in approximately 96% of cases. Typically,
one eye is affected earlier, and the disease progresses further
than in the fellow eye. Keratoconus is often diagnosed in
persons in their early teens to early twenties.
There does not appear to be a significant difference in the
incidence of keratoconus between left and right eyes nor
between male and female subjects.

Histopathologic changes
It is still unclear what causes the corneal
changes that occur in keratoconus. A triad of
classic histopathologic changes has been
observed:
1. Thinning of the corneal stroma.
2. Breaks in bowman's layer.
3. Iron deposition in the basal layers of the
corneal epithelium( Fleischer’s ring).

Etiology Of KC
1. Heredity
2. Eye rubbing and atopy
3. Contact lens wear
4. Abnormalities in ocular rigidity
and structure

Associations
 Ocular associations include:
1. vernal keratoconjunctivities,
2. blue sclera,
3. aniridia,
4. ectopia lentis,
5. Leber congenital amaurosis and
6. retinitis pigmentosa.

predisposing factors
1. Rigid contact lens wear and
2. Constant eye rubbing have also
been proposed as predisposing
factors.

By keratometry keratoconus is
classified as mild (48 D),
moderate (48- 54D) and severe
(54D). Morphologically, the
following are the three types:
1. Nipple ‫حلمة‬ cones,
characterized by their small
size (5mm) and steep
curvature. The apical center is
often either central or
paracentral and displaced
inferonasally
Classification and progressionClassification and progression

2. Oval cones or
sagging‫لى‬ّ‫ة‬‫يتد‬ . ‫يرتخي‬ ,
which are larger than
the nipple form
equals
5-6mm, ellipsoid‫م‬ٌ ‫ان‬‫س‬َّ‫م‬ ‫ج‬َ a ‫م‬ُ‫ض‬
‫ق ص‬ِ‫قي‬‫نا‬ and commonly
displaced
inferotemporally.
Classification andClassification and
progressionprogression

3. Globus cones,
which are the
largest 6mm
and may involve
over 75 % of the
cornea.
Classification andClassification and
progressionprogression

Clinical picture/ symptoms
1. Presentation is with impaired vision in one eye
caused by progressive astigmatism and myopia.
2. The patient may report frequent changes in
spectacle prescription or decreased tolerance to
contact lens wear.
3. As a result of the asymmetrical nature of the
condition, the fellow eye usually has normal vision
with negligible astigmatism at presentation, which
however, increases as the condition progresses.

1. Direct ophthalmoscopy
2. Retinoscopy
3. Slitlamp biomicroscopy
4. Keratometry
5. Placido disc
6. Corneal topography
7. Videokeratoscopy signs
Clinical picture/DIAGNOSIS

Often subtle, can be detected
as follows:
1. Direct ophthalmoscopy
from a distance of one foot
shows an “oil droplet”
reflex
2. Retinoscopy shows an
irregular “scissor” reflex.
Clinical picture/ Early signs

Slitlamp biomicroscopy
shows very fine,
vertical, deep stromal
striae ( vogt lines)
which disappear with
external pressure on
the globe.
Prominent corneal nerves
may also be present.

Keratometry shows
irregular
astigmatism where
the principal
meridians are no
longer 90 degree
apart and the mires
cannot be
superimposed.

 Videokeratoscopy signs:
1. Compression of mires in
affected region.
2. Color map showing
increased power in isolated
area of cone .
3. Inferior- superior dioptric
asymmetry.

These devices are used to detect and
quantify corneal surface curvature and the
presence of astigmatism. A keratoscope
uses light to project rings on the cornea.
Observation through the keratoscope of
the reflection of light from the cornea
and inspection of the shape and spacing of
the rings provide information about the
degree of astigmatism.
Keratoscope and videokeratoscope

A keratoscope fitted with a video camera is
called a videokeratoscope.
A videokeratoscope is the most common
instrument used to quantify the change in
corneal surface curvature, in a process
called corneal topography.

Placido disk and keratoscope
•Photokeratoscopy, which employ optical
principles that are similar to those of the
keratometer, measure a larger surface
area and provide a more complete
appreciation of corneal shape.

Klein hand-held keratoscope and
Placido disk

Videokeratography of with-the-rule, against-the
rule, oblique regular astigmatism

Corneal topography is
the most sensitive
method for
detecting very early
keratoconus.

Large Inferior Cone Superior coneSmall nipple cone

Clinical picture/ Late signs
• Late signs:
1. Slit lamp shows:
 Progressive corneal thinning, to as little
as one – third of normal thickness,
 Marked increase of the depth of A C
2. Associated with poor visual acuity
resulting from marked irregular myopic
astigmatism with steep keratometry (k)
readings.
3. Bulging of the lower lid in down gaze
(Munson’s sign)

4. Epithelial iron deposits
(Fleischer’s ring) may
surround the base of the
cone and are visualized
best with a cobalt blue
filter of the slit lamp
5. Stromal scarring in
severe cases.

 6.Acute hydrops is an acute influx
of aqueous in to the cornea as a
result of a rupture in descemet
membrane. This causes a sudden
drop in visual acuity associated
with discomfort and watering.
Although the break usually heals
within 6-10 weeks and the corneal
oedema clears, avariable amount of
stromal scarring may develop.

 Acute hydrops are initially
treated with hypertonic
saline and patching or a
soft bandage contact lens.
 Healing may result in
improved visual acuity as
a result of scarring and
flattening of the cornea.
Keratoplasty should be
deferred‫يرجئ‬ . ‫جل‬ِّ ‫يؤ‬ until
the oedema has resolved.

Differential diagnosis
1. Corneal Warpage ‫ج‬َ a ‫و‬َّ‫م‬ ‫ع‬َ a Syndrome
2. High-riding rigid Gas-permeable lens
3. Keratoglobus

The topography of keratoconus: LECTURE 8The topography of keratoconus: LECTURE 8
The photokeratoscope orThe photokeratoscope or placido discplacido disc can provide ancan provide an
overview of the cornea and can show the relativeoverview of the cornea and can show the relative
steepness of any corneal area.steepness of any corneal area.
keratoconic corneakeratoconic cornea Normal corneaNormal cornea

EyeSys System
The corneal surface has 75% of the refractive or light
focusing ability of the eye. The EyeSys System
utilizes placido disk technology to acquire images of
the corneal surface. Placido disk technology is
based on a technique that captures the reflection of
rings of light off the surface of the cornea and
measures the different distances between the ring
reflections.
Current software technology captures the reflected
images with a digital camera, processes ‫يعالج‬ . ‫يعامل‬ُ
the data, and displays‫باداء‬ْ‫اد‬‫إ‬ِ‫ب‬ ; ‫ن ة‬َ‫ة‬‫با‬َ‫ة‬‫إ‬ِ‫ب‬ the information in
multiple formats.

A Placido device is made up
of many concentric light rings.
The exact arrangement and
number of rings may vary with
different manufacturers
Light rings are projected on the
cornea above.This image is
captured and analyzed as
thousands of computations are
performed instantly.

corneal topography
‫ش ف‬ِ‫ ف‬ ‫ك‬ْ‫ِش‬ ‫ت‬َ‫ْك‬‫س‬ْ‫ِش‬ ‫م‬ُ‫س‬ ; ‫ فاف‬‫ش‬َّ‫ا‬ ‫ك‬َ‫ْك‬

• The map above was taken prior to simulated
treatment. The horizontal red and orange areas are
elevated above the cooler colors green blue areas
demonstrating this patient’s against the rule
astigmatism.

corneal topography
• The same map is below after LASIK simulated laser
treatment. Observe the more uniform neutral green
color centrally indicating a much smoother uniform
surface without astigmatism (corrected with
LASIK).

Photokeratoscopy view of early keratoconus
Note the pear-shaped ‫الشكل‬ ‫كمثري‬ pulling of
the central keratoscopy mires. The close
proximity of the rings (in the inferior-temporal
portion of the eye(
indicates corneal steepening
and greater distance between the rings
(in the superior-nasal portion of the eye(
indicates flattening.

corneal topography
• The typical spiral pattern of keratoconus
progression. The condition commonly begins in
the inferior-temporal quadrant, with the last area
of the cornea to be topographically affected in
the superior-nasal quadrant.
• In color-coded topographic images, red
represents steeper corneal curvature, and the
spectrum of yellow, green, and blue represents
progressively flatter curvatures.

corneal topography
• The nipple-shaped form of
keratoconus
demonstrates a small
central ectasis
surrounded by 360
degrees of “normal”
cornea.

corneal topography
The most striking features of the nipple topography
are:
• The often high degree of with-the-rule corneal
toricity confined to the central 5.0 mm of the cornea.
• The nearly 360 degrees of “normal” mid-peripheral
cornea that surrounds the base of the cone.
• The occasional presence of an elevated fibroplastic
nodule ‫ن ة‬َ‫ة‬‫ر‬َ‫ة‬ ‫د‬َ‫ة‬ at the apex of the cornea, hence the
name nipple keratoconus. The superficial nodules
are frequently eroded‫ت‬ّ ‫ح‬ُ ‫ي‬َ‫ة‬ . ‫كل‬ّ ‫يتأ‬ by the presence of
a rigid contact lens, often necessitating: rigid gas
permeable/soft contact lens (RGP/SCL( or
piggyback designs,

corneal topography
Nipple-shaped keratoconus may also manifest as a small
central ectasia with moderate to high with-the-rule corneal
astigmatism in the form of regular bow tie.

corneal topography
Oval-shaped keratoconus is hallmarked
by steepening of the inferior cornea

Globus-Shaped Topography
• The globus form of keratoconus affects the
largest area of the cornea, often encompassing
nearly three quarters(75%) of the corneal
surface.
• Due to its size, nearly all of the keratoscopy
rings will be encompassed‫ ن‬w‫م‬َّ‫ا‬ ‫ض‬َ‫ْك‬ ‫م‬ُ‫س‬ ; ‫ملول‬ُ‫س‬ ‫ش‬ْ‫ِش‬ ‫م‬َ‫ْك‬ within
the area of the ectasia. Unlike the advanced
forms of nipple or oval keratoconus, the globus
cone has no island of “normal” mid-peripheral
cornea above or below the midline.

Globus-Shaped Topography
Due to the size of the globus-shaped keratoconus, all
nine rings of the photokeratoscopy image are
encompassed by the conical area and no “islands”
of normal mid-peripheral cornea are seen.

Normal corneal topography
Five qualitative patterns of
normal corneal topography
using a normalized scale.
Top left, round; top center,
oval; top right, symmetric
bow-tie; bottom left, =
asymmetric bow tie;
bottom center, irregular. In
the normalized scale
(bottom right( the range of
dioptric power represented
by each color varies among
eyes, depending on the
degree of corneal
asphericity. Classification
of normal corneal
topography based on computer-assisted videokeratograph.

Keratoconus topography
• Videokeratographs mirror this distortion by
producing mires that are typically oval. The
distance between rings is smallest at the
steepest corneal slope and farthest apart
superiorly where the cornea is flattest.
• Tangential curvature maps of projection-based
systems provide additional information. On
these maps the steepest slope is easily located
as being inferior to the apex, producing an
asymmetric bow tie‫الشكل‬ ‫ي‬ّ ‫ش‬ِ‫ب‬ ‫فرا‬َ‫ة‬ ‫رقب ة‬ ‫رباط‬ . This
corresponds to the exaggerated prolate‫متطاول‬
shape of the keratoconic eye.
• Projection-based systems can be used to
locate the apex of the cone on elevation maps
as the highest point.

Axial map
• Axial map. Also called the power or
sagittal map, this output is the simplest
of all the topographical displays. It shows
variations in corneal curvature as
projections ‫ فاشة‬‫ش‬‫ال‬ ‫على‬ ‫المتحركة‬ ‫الصلور‬ ‫عرض‬
and uses colors to represent dioptric
values. Warm colors such as red and
orange show steeper areas; cool colors
such as blue and green denote the flatter
areas.

Sometimes referred to as the instantaneous‫،فورى‬ ‫ىروف، ىوتوى‬
‫لحظى‬ , local, or true map, it also displays the cornea
as a topographical illustration, using colors to
represent changes in dioptric value. However, the
tangential strategy bases its calculations on a
different mathematical approach that can more
accurately determine the peripheral corneal
configuration.
Tangential ‫ي‬ّ ‫س‬ّ ‫ما‬َ ‫م‬ُ map

Tangential map
• It does not assume the eye is spherical, and
does not have as many presumptions‫رض‬ْ‫ِش‬ ‫ف‬َ‫ْك‬ as
the axial map regarding corneal shape.
• In fact it is the map that more closely represents
the actual curvature of the cornea over the axial
map. The tangential map recognizes sharp
power transitions more easily than the axial
map, and eliminates the smoothing
appearance that appears on the axial map.

This utilizes yet another algorithm to give additional
information about the cornea. An elevation map shows
the measured height from which the corneal curvature
varies (above or below) from a computer-generated
reference surface. Warm colors depict . .‫صف‬ِ ‫ي‬ ‫ور‬ّ ‫يص‬ ‫يرسم‬
points that are higher than the reference surface; cool
colors designate lower points.
This map is most useful in predicting fluorescein
patterns with rigid lenses. Higher elevations (reds)
represent potential areas of lens bearing, while the
lower areas (greens) will likely show fluorescein
pooling.
Elevation map.

Progressive Nipple Keratoconus

corneal topography
•Corneal topography and imaging.
Symmetric bow tie typical for regular
astigmatism.

corneal topography
•This elevation map shows inferior thinning
in a patient's left eye.

Treatment Of
keratoconus
Non-
surgical
Surgical
Spectacles
Contact lenses Penetrating
Keratoplasty
Lamellar
Keratoplasty
Lamellar
keratoplasty
Intracorneal rings
Other Surgery
C3RC3R

Treatment that preventTreatment that prevent
progression of KCprogression of KC
Collagen cross linking treatments (C3RCollagen cross linking treatments (C3R))
Recent treatment which is based on strengthenRecent treatment which is based on strengthen
the cross-linking of corneal collagen by utilizesthe cross-linking of corneal collagen by utilizes
riboflavin and ultraviolet (UV) light exposureriboflavin and ultraviolet (UV) light exposure..
During the 30-minute riboflavin eyedrops areDuring the 30-minute riboflavin eyedrops are
applied to the cornea, which are then activatedapplied to the cornea, which are then activated
by a UV light. This is the process that has beenby a UV light. This is the process that has been
shown in laboratory and clinical studies toshown in laboratory and clinical studies to
increase the amount of collagen cross-linking inincrease the amount of collagen cross-linking in
the cornea and strengthen the corneathe cornea and strengthen the cornea..

Collagen cross linking treatments causes theCollagen cross linking treatments causes the
collagen fibers to thicken, stiffen, crosslink collagen fibers to thicken, stiffen, crosslink
re-attach to each other, making the corneare-attach to each other, making the cornea
stronger and more stable thus convincinglystronger and more stable thus convincingly
halting the progression of the disease. Thehalting the progression of the disease. The
figures below demonstrate almost 10 dioptersfigures below demonstrate almost 10 diopters
of corneal flattening in one patient before (left)of corneal flattening in one patient before (left)
after this combined treatment (rightafter this combined treatment (right).).

Advantages ofAdvantages of
C3RC3R::
1.1. Simple one time treatmentSimple one time treatment
2.2. No periodic treatments requiredNo periodic treatments required
3.3. Halts the progress and causes someHalts the progress and causes some
regressionregression
4.4. It is permanentIt is permanent
5.5. No handling of lenses every dayNo handling of lenses every day
6.6. Does not need any eye donationDoes not need any eye donation
7.7. No precautionNo precaution
8.8. No injectionNo injection
9.9. No stitches as in keratoplastyNo stitches as in keratoplasty
10.10. No incisions as in IntacsNo incisions as in Intacs
11.11. Quick recovery, short follows upQuick recovery, short follows up

spectacle lensesspectacle lenses
As keratoconus progresses,As keratoconus progresses, spectacle lensesspectacle lenses often fail tooften fail to
provide adequate visual acuityprovide adequate visual acuity::
1.1. EspeciallyEspecially at night.at night.
2.2. This can be further complicated by the fact that theThis can be further complicated by the fact that the
patient's glasses prescription maypatient's glasses prescription may change frequentlychange frequently duedue
to the disease progress and can be limited by the degreeto the disease progress and can be limited by the degree
ofof myopia and astigmatismmyopia and astigmatism that must be corrected.that must be corrected.
3.3. Also, keratoconus is often asymmetric therefore fullAlso, keratoconus is often asymmetric therefore full
spectacle correction may be intolerable because ofspectacle correction may be intolerable because of
anisometropia and aniseikoniaanisometropia and aniseikonia..
However, despite these limitations, spectacles can oftenHowever, despite these limitations, spectacles can often
provide surprisingly good visual results in theprovide surprisingly good visual results in the early stagesearly stages
of the condition.of the condition.

contact lenses
Contact lens options for keratoconusContact lens options for keratoconus
• When a keratoconic patient is no longer able toWhen a keratoconic patient is no longer able to
obtain good visual acuity with spectacle lensesobtain good visual acuity with spectacle lenses
because of increasing levels of irregular myopicbecause of increasing levels of irregular myopic
astigmatism and higher-order aberrations, rigidastigmatism and higher-order aberrations, rigid
contact lenses will be required, effectively tocontact lenses will be required, effectively to
provide a new anterior surface to the eye.provide a new anterior surface to the eye.
• Contact lenses are considered when vision isContact lenses are considered when vision is
not correctible to 6/9 by spectaclesnot correctible to 6/9 by spectacles and patientsand patients
become symptomatic.become symptomatic.

contact lenses
The successful fitting of contact lenses forThe successful fitting of contact lenses for
keratoconus requires that three objectiveskeratoconus requires that three objectives‫أهداف‬‫أهداف‬
be met :be met :
1.1. The lens-to-cornea fitting relationship shouldThe lens-to-cornea fitting relationship should
create the least possible physicalcreate the least possible physical traumatrauma to theto the
cornea.cornea.
2.2. The lens should provideThe lens should provide stable visual acuitystable visual acuity
throughout the patient's entire wearingthroughout the patient's entire wearing
schedule.schedule. ‫ل‬َ‫ْك‬ ‫و‬َ‫ْك‬ ‫د‬ْ‫ِش‬ ‫ج‬َ‫ْك‬‫ل‬َ‫ْك‬ ‫و‬َ‫ْك‬ ‫د‬ْ‫ِش‬ ‫ج‬َ‫ْك‬
3.3. The lens should provideThe lens should provide all day wearing comfort.all day wearing comfort.

Lens Designs for KeratoconusLens Designs for Keratoconus
Soft lensesSoft lenses
Soft lenses have a limited role in correcting cornealSoft lenses have a limited role in correcting corneal
irregularity, as they tend to drapeirregularity, as they tend to drape‫على‬ ‫ل‬ّ ‫اد‬َ‫ة‬‫مت‬‫على‬ ‫ل‬ّ ‫اد‬َ‫ة‬‫مت‬ over theover the
surface of the cornea and result in poor visualsurface of the cornea and result in poor visual
acuity .acuity .
Hence, soft lenses are used only in theHence, soft lenses are used only in the earlyearly
stages of the diseasestages of the disease. In such cases, the lenses. In such cases, the lenses
are usually toric, and are fitted in the sameare usually toric, and are fitted in the same
manner, as they would be on a patient withmanner, as they would be on a patient with
myopic astigmatism. The fitting procedure beginsmyopic astigmatism. The fitting procedure begins
by placing a soft lens with powers equal to theby placing a soft lens with powers equal to the
manifest refraction vertexedmanifest refraction vertexed ‫القم ة‬ ‫على‬to the plane ofto the plane of
the cornea on the eye. Final lens power is bestthe cornea on the eye. Final lens power is best
calculated by performing a sphero-cylindercalculated by performing a sphero-cylinder
refraction.refraction.

Toric soft contact lenses for earlyToric soft contact lenses for early
KCKC

soft contact lenses for early KCsoft contact lenses for early KC
•However, some hydrogel lenses have been designedHowever, some hydrogel lenses have been designed
specially for keratoconus.specially for keratoconus. Hydrogel lenses are made
relatively large in diameter, usually 13.5 to 14.5 mm in
diameter which results in the lens edge being beyond the
limbus on the sclera.
•They are designed to be thicker than regular soft lensesThey are designed to be thicker than regular soft lenses
so they retain a rigid shape to some extent. For thisso they retain a rigid shape to some extent. For this
reason they compress the central cornea and partiallyreason they compress the central cornea and partially
trap atrap a tear pooltear pool, as with rigid corneal lenses. In effect,, as with rigid corneal lenses. In effect,
they are rigid lenses made from hydrogel materials, andthey are rigid lenses made from hydrogel materials, and
they do appear to be giving a reasonable visual resultthey do appear to be giving a reasonable visual result
with some types of keratoconuswith some types of keratoconus..

HYDROGEL (SOFT) LENSES
• Hydrogel lenses increase the amount of oxygen
reaching the cornea as do most contact lenses.
By making
the lenses thinner or increasing the water
content, or both, more oxygen will reach the
cornea. It is not uncommon to have hydrogel
lenses made as thin as 0.035 mm.
• Lenses are available up to about 75% water
content with most lenses being used today
range from 38% to 65% water .
Thick
Thin

Criteria to useCriteria to use::
1.1. One criterion to use to determine if softOne criterion to use to determine if soft
lenses are acceptable is that they shouldlenses are acceptable is that they should
induce no scarring. Often, soft contactinduce no scarring. Often, soft contact
lenses lead to repeated corneallenses lead to repeated corneal
abrasions, which can result in scarring.abrasions, which can result in scarring.
2.2. Another criterion is the patient must beAnother criterion is the patient must be
happy with his vision and is able tohappy with his vision and is able to
function properly in their daily activities.function properly in their daily activities.

AdvantagesAdvantages
1) They afford higher levels of1) They afford higher levels of comfortcomfort andand
longer wearing times, especially inlonger wearing times, especially in
patients intolerant to RGP corneal lensespatients intolerant to RGP corneal lenses
or in monocular keratoconus.or in monocular keratoconus.
2) They are useful where the cone apex2) They are useful where the cone apex
may bemay be displaceddisplaced, especially if it is very, especially if it is very
low.low.
3) They are relatively3) They are relatively simple to fitsimple to fit..

DisadvantagesDisadvantages
1) Visual acuity may be variable (less corrected) in1) Visual acuity may be variable (less corrected) in
cases of very high minus lenses.cases of very high minus lenses.
2) Low-powered2) Low-powered diagnosticdiagnostic lenses may not providelenses may not provide
an accurate guide to the fit of thean accurate guide to the fit of the final lensfinal lens,,
which may be extremely high powered.which may be extremely high powered.
3) If the condition (KC) has progressed, it may be3) If the condition (KC) has progressed, it may be
difficult to change to RGP lenses at a laterdifficult to change to RGP lenses at a later
stage.stage.

Rigid gas permeable lensesRigid gas permeable lenses
Rigid gas permeable (RGP) corneal lenses are theRigid gas permeable (RGP) corneal lenses are the
lenses of first choice for correcting keratoconus.lenses of first choice for correcting keratoconus.
They provide the best possible vision with theThey provide the best possible vision with the
maximum comfort so that the lenses can be wornmaximum comfort so that the lenses can be worn
for a long period of timefor a long period of time..
The purpose of the lens is to cover the irregularThe purpose of the lens is to cover the irregular
astigmatism and the disordered anterior surfaceastigmatism and the disordered anterior surface
optics of an ectatic cornea by providing a regular,optics of an ectatic cornea by providing a regular,
spherical, optic surface before the eye (Figurespherical, optic surface before the eye (Figure
below). The lens does not retard the progressionbelow). The lens does not retard the progression
of the diseaseof the disease..

Rigid gas permeable lensesRigid gas permeable lenses

RGP contact lenses are primaryRGP contact lenses are primary
option for correcting KC visionoption for correcting KC vision
Keratoconic cornea
RGP
lens

Piggyback Soft LensesPiggyback Soft Lenses
• The technique of placing a rigid contact lens on top ofThe technique of placing a rigid contact lens on top of
a soft lens (piggyback) was first described in the mida soft lens (piggyback) was first described in the mid
1970’s. Early piggyback systems consisted of thick,1970’s. Early piggyback systems consisted of thick,
low Dk, soft lenses in combination with low Dklow Dk, soft lenses in combination with low Dk
silicone/acrylate rigid lenses. It was not surprising thatsilicone/acrylate rigid lenses. It was not surprising that
this combination frequently resulted in corneal hypoxiathis combination frequently resulted in corneal hypoxia
and neovascularisation, which limited its usefulness.and neovascularisation, which limited its usefulness.
However, with the recent introduction of high DkHowever, with the recent introduction of high Dk
silicone hydrogel lenses and stable high Dk GPsilicone hydrogel lenses and stable high Dk GP
materials, the dual lens system is now enjoying amaterials, the dual lens system is now enjoying a
rebirth, particularly for keratoconus patientsrebirth, particularly for keratoconus patients
experiencing comfort or lens position issueexperiencing comfort or lens position issue‫ف ذ‬َ‫ْك‬‫مفن‬َ‫ْك‬ . ‫ر ج‬َ‫ْك‬ ‫مرخ‬َ‫ْك‬‫ف ذ‬َ‫ْك‬‫مفن‬َ‫ْك‬ . ‫ر ج‬َ‫ْك‬ ‫مرخ‬َ‫ْك‬
..

Flexlens Piggyback lensFlexlens Piggyback lens

A recent piggyback lens system forA recent piggyback lens system for keratoconuskeratoconus
consisting of a high Dk soft lens and an RGP lensconsisting of a high Dk soft lens and an RGP lens
combinationcombination..
A rigid lens riding piggyback over a soft lens.

Scleral lensesScleral lenses
• Scleral lenses play a very significant roleScleral lenses play a very significant role
in cases of advanced keratoconus wherein cases of advanced keratoconus where
corneal lenses do not work and cornealcorneal lenses do not work and corneal
surgery is contra-indicated. Scleralsurgery is contra-indicated. Scleral
lenses completely neutralize any corneallenses completely neutralize any corneal
irregularity and can help patientsirregularity and can help patients
maintain a normal quality of life. Thesemaintain a normal quality of life. These
are large diameter lenses (23-25mm)are large diameter lenses (23-25mm)
that rest on the sclera, and vaults overthat rest on the sclera, and vaults over
the cornea .the cornea .

A scleral and a corneal lens toA scleral and a corneal lens to
compare the sizecompare the size..
Because of their size, they doBecause of their size, they do
not fall out; dust or dirtnot fall out; dust or dirt
particles cannot get behindparticles cannot get behind
them during wear. They arethem during wear. They are
surprisingly comfortable tosurprisingly comfortable to
wear because the edges ofwear because the edges of
the lens rests above andthe lens rests above and
below the eye lid margins sobelow the eye lid margins so
there is no lens awareness.there is no lens awareness.
The introduction of rigid gasThe introduction of rigid gas
permeable (RGP( materialspermeable (RGP( materials
has made this design morehas made this design more
readily availablereadily available..

Scleral lensesScleral lenses
AdvantagesAdvantages
1.1. Comfortable to eyes.Comfortable to eyes.
2.2. Any type of corneal irregularity is corrected.Any type of corneal irregularity is corrected.
3.3. Easy to store.Easy to store.
4.4. Long life.Long life.
DisadvantagesDisadvantages
1.1. Much chair time is needed.Much chair time is needed.
2.2. A very specialized fitting techniqueA very specialized fitting technique .

Rose K lensRose K lens
•The Rose K lens is probably the most widelyThe Rose K lens is probably the most widely
fitted keratoconus lens worldwide and achievesfitted keratoconus lens worldwide and achieves
an 85% first fit success in the UK. The Rose Kan 85% first fit success in the UK. The Rose K
lens design is alens design is a fully flexible lensfully flexible lens that works wellthat works well
onon early to advanced keratoconus patientsearly to advanced keratoconus patients ..
Complex lens geometry, combined with theComplex lens geometry, combined with the
enhanced material benefits makes the Rose Kenhanced material benefits makes the Rose K
lens the good fit enhancing patient comfort andlens the good fit enhancing patient comfort and
visual acuity. Multiple parameters make fittingvisual acuity. Multiple parameters make fitting
the Rose K lens possible for most keratoconicthe Rose K lens possible for most keratoconic
eyes. The design starts with a standard 8.7mmeyes. The design starts with a standard 8.7mm
diameter and works by decreasing the opticdiameter and works by decreasing the optic
zone diameter as the base curve gets steeperzone diameter as the base curve gets steeper..

Rose K™Rose K™ contact lens with smallcontact lens with small
optic zoneoptic zone

The Rose K™ lensThe Rose K™ lens
Rose K lensRose K lens

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