Principle, Optics, History, Illumination techniques, Uses Of The Slit Lamp Bi-microscope.

1. SLITLAMP BIMICROSCOPY
(Principle,
Instrumentation,Illumination,
andUses)
By OSOATA OBEHI O.D

2. OUTLINE
• INTRODUCTION
• HISTORY
• WORKING PRINCIPLE
• COMPONENTS OF A SLITLAMP
• ILUMINATION SYSTEM
• OBSERVATION SYSTEM
• MECHANICAL SYSTEM
• ILLUMINATION TECHNIQUES AND THEIR APPLICATION
• OCULAR TISSUES AND POSSIBLE ABNORMALITIES
• RECORDING
• ACCESSORIES USED WITH THE SLITLAMP

3. Introduction
• The slit lamp is the most flexible and widely-
used instrument for ophthalmic diagnosis. it
enables the practitioner to observe the living
tissue of eye under magnification and allows
quantitative measurements and photography
of every part for documentation.

4. Ocular Structures that can be examined with the
slitlamp bimicroscope include:
• Eyelid
• Cornea
• Sclera
• Conjunctiva
• Iris
• Aqueous
• Natural crystalline lens
• Anterior vitreous

5. Other Uses Of Slitlamp Bimicrosope:
• Fundus examination with the use of high
power lenses eg +60 ,+90, -58D and -65D in
form of a contact lens.
• Mechanical and optical support for many
accessories eg Tonometer, Goniosopy,
cameras
• Beam delivery devices for visually controlled
laser treatment eg laser photocoagulation.

6. HISTORY
Alvar Gullstrand 1911 created first slit projector
Otto Henker devised an arm to support Czapski corneal loupe.
Hans Goldmann 1933 created a joystick to focus the two components
this evolved the model for today's HAAG STREIT slit lamps .
Wilhelm Comberg 1933 created vertically downward illumination
system
Hans Littmann in 1953 combined both Goldmann and Comberg's
systems thereby creating the model for today's ZEISS slit lamps.

7. GULLSTRAND
OPHTHALMOMICROSCPE (1911)

8. 1940 Hamblin UK Slitlamp
Littmann Type Zeiss Slit
lamp

10. ZEISS SLITLAMP

11. HAAG STREIT SLITLAMP

12. WORKING PRINCIPLE
An intense light beam entering a dark room through a
tight window slit causing dust particles become visible
which could never be seen if the room were brightly
illuminated.
With a narrow slit and a sufficiently small aperture
angle, the illumination beam has a shape defined by
two knife edges placed end to end.
When the beam passes through transparent structures
in the anterior part of the eye, it is scattered at
microscopically small inhomogeneities. The slit-shaped
scattering image of the structures is referred to as the
optical section.

13. Figure 6.38 (a) Front view of an eye
in normal
(diffuse) illumination. The cornea can
only be
recognized via reflections (Purkinje
image).
(b) Front view of the eye with slit
illumination
in which the scattering images provide
an optical
sectioning. With such an illumination
technique, we can also see the cross-
sections
of cornea and eye lens.

14. MAJOR COMPONENTS OF A SLITLAMP
ILLUMINATION
SYSTEM
1
OBSERVATION
SYSTEM
2
MECHANICAL
SYSTEM
3

15. ILLUMINATION SYSTEM
A bright ,focal source of light with a slit
mechanism Provides an illumination of
2*10^5 to 4*10^5lux.
The beam of light can be changed in
intensity,height,width,direction or angle
and color during the examination with the
flick of lever.

16. Condensing lens system:
Consist of a couple of planoconvex
lenses with their convex surface in apposition.
Slit and other diapharm:
Height and width of slit can be varied by using knobs.
Projection lens:
Form an image of slit at eye.
Advantages
1.keeps the aberration of lens down.
2.increase the depth of focus of slit.

17. Light sources: tungsten and
halogen filament bulbs are used
although , LEDs are increasingly
replacing the classic light sources.
Formation of the slit image:
Based on Kohler-type
illumination.

18. FORMATION OF SLIT IMAGE

19. ILLUMINATION FILTERS

20. OBSERVATION SYSTEM
Includes the eye piece and
objective lenses.
The objective lens consists
of two planoconvex lenses
with their convexities put
together providing a
composite power of +22D.
Binocular Microscope
consists of two eye piece
each having a +10D lens.
Prisms are placed between
the objective and eyepiece
to reinvert the image.
Most slit lamp provide a
range of magnification from
6x to 50x.

21. Optics of Observation System

22. MECHANICAL SYSTEM
• Includes the mechanical adjustments and
rests to aid ease of examination and better
assessment of ocular tissues.
• Components of the mechanical system :
 Three- coordinate Joystick
 Headrest
 Chin rest
 Rotary axis
 Canthus alignment
 Magnification and Filter Changers etc.

23. Rotary Axis
biomicroscope
Changing filters
Magnification changer
Patient positioning

25. ILLUMINATION TECHNIQUES
• Diffuse illumination
• Direct illumination
o Parallilepiped
o Optic section
o Conical(pinpoint)
o Tangential
o Specular reflection
• Indirect illumination
o Retro-illumination
o Sclerotic scatter
o Transillumination
o Proximal illumination

26. DIFFUSE ILLUMINATION
• Angle between microscope and illumination system should be 30-45 degree.
• Slit width should be widest.
• Filter to be used is diffusing filter.
• Magnification: low to medium
• Illumination: medium to high.
Applications:
– General view of anterior of eye: lids,lashes,sclera,cornea ,iris, pupil,
– Gross pathology and media opacities
– Contact lens fitting.
– Assessment of lachrymal reflex.

28. • Involves placing the light source at an angle of about
40-50 degree from microscope.
• This arrangement permits both light beam and
microscope to be sharply focused on the ocular tissue
being observed.
• Wide beam direct illumination is commonly used as
a preliminary technique to evaluate large area
• it is particularly suitable for assessment of
cataracts,scars,nerves,vessels etc.
• It is also of great importance for the determination
of stabilization of axis of toric contact lens.

29. (a) Observed cross-section of the
cornea (framed) with direct focal
illumination and
.
(b) corresponding schematic cross-section
of the (sliced) cornea

30. TYPES OF DIRECT ILLUMINATION TECHNIQUES
Parallelepiped:
Constructed by narrowing the beam to 1-2mm in width to illuminate a rectangular area of cornea.
Microscope is placed directly in front of patients cornea.
Light source is approximately 45 degree from straight ahead position.
Applications:
Used to detect and examine corneal structures and defects.
Used to detect corneal striae that develop when corneal edema occurs with hydrogel lens wear and in
keratoconus.
Higher magnification than that used with wide beam illumination is preferred to evaluate both depth
and extent of corneal, scarring or foreign bodies.

31. Click to add text

32. Conical beam(pinpoint)
– Produced by narrowing the vertical height of a parallelepiped to
produce a small circular or square spot of light.
– Light source is 45-60 degree temporally and directed into pupil.
– Magnification: high(16-25x)
Application
Used to examined the transparency of the anterior chamber for
floating cells in anterior uveitis.

34. Optic section
1
Optic section is
a very thin
parallelepiped
and optically
cuts a very thin
slice of the
cornea.
2
Angle between
illuminating
and viewing
path is 45
degree.
3
With wider slit
their extension
and shape are
visible more
clearly.
4
Magnification:
maximum.
5
Application
6
Assess depth
and portion of
obejects eg
foreign body
and during
contact lens
fitting
7
Examination of
AC depth is
performed by
wider slit width
1-3mm .

35. Used to localize:
• Nerve fibers
• Blood vessels
• Infiltrates
• Cataracts
• AC depth.
Optical section of lens

36. Tangential illumination
• A narrow light beam is projected almost paralell along
the structure to be observed.
• Elevated structures are visible by shadowing
• Illumination angle: 90 degree.
• Medium –wide beam of moderate height is
used.
• Magnification of 10-25x
Application:
• Anterior and posterior cornea
• Elevated abnormalities, changes in the iris, cysts and
tumors.
• Anterior lens (especially useful for viewing
pseudoexfolation).

38. Specular reflection
• Angle of illuminator to microscope must be
equal and opposite. Each should be 30
degrees apart.
• Angle of light should be moved until a very
bright reflex obtained from corneal surface is
called zone of specular reflection.
• Under specular reflection anterior corneal
surface appears as white uniform surface and
corneal endothelium takes on a mosaic
pattern.

39. • Application:
• Evaluate general appearance of corneal
endothelium
• Lens surfaces
• Cornea endothelium
Example of tangential illumination (iris). Example of specular reflection.

40. INDIRECT ILLUMINATION
The beam is focused in an
area adjacent to ocular
tissue to be observed hence
light reflected by internal
structures illuminates
structure to be examined.
The axis of the slit light is
±4°horizontally away from
the normal position.
Magnification: 12x and
above

41. • Main application: Examination of objects in
direct vicinity of corneal areas of reduced
transparency eg, infiltrates, corneal scars,
deposits, epithelial and stromal defects.

42. OCULAR TISSUE POSIBLE ABNORMALITIES
GLOBE Irregular size shape or position (microphthalmus,
bupthalmos, strabismus)
ORBIT Gross anatomical abnormalities (endopthalmos,
exophthalmos, palpable masses, crepitus)
EYELIDS Anatomic (entropion, ectropion,eublepharon, trichiasis),
Introduced(lacerations, notches), Dermal(dermatitis,
erythema, alopecia, depigmentation, crusts, ulcers),
Glandular(meibomianitis) abnormalities
NASOLACRIMAL
APPARATUS
Discharge(serus, mucus, encrusted) obstructed or
impeforated punta, masses within canaliculi
SCLERA Vascular injection,Hemorrhage, cellular infiltration,masses
CONJUCTIVA Hyperemia, hemorrhage, chemosis, folicularization,
chemosis, symblepharon, cellular infiltration, massses.
CORNEA Microcornea, edema, laceration, fibrosis, vascularization,
cellular infiltrartion, iris prolapse, nodules etc
ANTERIOR CHAMBER Depth, hyphema, hypopyon, iris cysts, vitreous prolapse,
lens luxation,fibrous clots,
persistent pupilary membranes etc
IRIS Thickening, synechae,hyperpigmentation, rubeosis iris,

43. RECORDING
OCULAR TISSUE RE LE
GLOBE NORMAL NORMAL
ORBIT NORMAL NORMAL
EYELIDS NORMAL NORMAL
NASOLACRIMAL
APPARATUS
NORMAL NORMAL
SCLERA NORMAL NORMAL
CONJUCTIVA CLEAR CLEAR
CORNEA CLEAR CLEAR
ANTERIOR CHAMBER DEEP DEEP
IRIS NORMAL NORMAL
LENS CLEAR CLEAR
Ensure you record the type of abnormalities seen in case present.

44. SOME OPTICAL ASSESORIES USED
WITH THE SLITLAMP
Scleral lens +90D volk lens
+78D Volk lens

45. Goldmann Applanation
Tonometer Gonio lens
Ruby lens
Image of Posterior eye examination

47. THANK YOU