Contrast sensitivity

1. CONTRAST SENSITIVITY
PRESENTER; DR. LEENA VADHEL
MODERATOR: DR. MRUDULA BHAVE

2. Definition:
Contrast:- defined as the degree of blackness to
whiteness of target.
Contrast threshold:-is the smallest amount of
contrast required to be able to see the target.
Contrast sensitivity:- is the reciprocal of the
contrast threshold.

3. WHAT IS CONTRAST SENSITIVITY
the ability to perceive slight changes in
luminance between regions which are not
separated by definite borders and is just as
important as the ability to perceive sharp
outlines of relatively small objects.

4. SNELLENS VISUAL ACUITY VERSUS
CONTRAST SENSITIVITY
Snellen’s charts test VA at a very high contrast
thus many patients have a good snellens VA but
they may be visually handicapped in real life
situations.
The VA drops in the situations with low contrast
and the quality of vision is not good.
It provides the information that cannot be
obtained from visual acuity, and it is often a
better predictor of visual performance then VA.

5. CONTRAST SENSITIVITY CURVE
C .S is presented
as curve which
plots the lowest
contrast level a
patient can detect
for specific size
target.
The x-axis curve is
for spatial
frequency, y-axis
is for contrast
sensitivity.

6. CONTRAST SENSITIVITY FUNCTION
 The contrast sensitivity function proposed
by Manos and Sakrison.
A plot of CS over a range of spatial
frequencies gives the contrast sensitivity
function(CSF).
Contrast sensitivity depends on spatial
frequency.
Spatial frequency of visual stimuli is given in
cycles per degree.

7. CONTRAST SENSITIVITY FUNCTION
Contrast sensitivity function (CSF) is a
subjective measurement of a person's ability
to detect a low contrast pattern stimuli,
usually vertical stripes of decreasing shades
of black to grey. The resulting measurement
is said to give a more accurate
representation of the eyes' visual
performance.

8. CONTRAST SENSITIVITY FUNCTION
CSF has a peak value
of approximately 1 to 8
cycles/ degree.
Distinction of high
frequencies not
possible because of
limited number of
photoreceptors.

9. CONTRAST SENSITIVITY FUNCTION
Neural and optical
attenuation limits
the high spatial
frequency CS.
Point where the
CSF cuts the x axis
is called cut off
frequency.

10. MICHELSON FORMULA:
L max- Lmin/Lmax+Lmin
Lmax = Luminance on the lighter surface
Lmin = Luminance on the darker surface
WEBERS FORMULA:
Defined as ( Lb – Lt ) / Lb
Lb & Lt are the luminance of the background and
target respectively.
Weber contrast used in calculating the contrast of
letters.

11. low medium high
object:
100%
contrast
image
spatial frequency
contrast
1
0

12. • The modulation transfer function (MTF) indicates the ability of an
optical system to reproduce (transfer) various levels of detail (spatial
frequencies) from the object to the image.
• Its units are the ratio of image contrast over the object contrast as a
function of spatial frequency.
• It is the optical contribution to the contrast sensitivity function (CSF).

13. MTF: Cutoff FrequencyMTF: Cutoff Frequency
0
0.5
1
0 50 100 150 200 250 300
1 mm
2 mm
4 mm
6 mm
8 mm
modulationtransfer
spatial frequency (c/deg)
cut-off frequency
57.3
cutoff
a
f
λ
=
⋅
Rule of thumb: cutoff
frequency increases by
~30 c/d for each mm
increase in pupil size

14. Gratings
One adjacent pair of light and dark bars
makes up one cycle.
The thickness of the grating is described by
their spatial frequency in cycles per degree
of the visual angle at the eye..
Large number of grating can fit with in a
degree of visual angle

15. Gratings
Gratings are broader and are of low spatial
frequency.
Spatial phase defines its position.
Change in spatial phase by 180 degrees
indicates that the grating is displaced by half
a cycle.

16. Sine wave gratings
These gratings are
lacking in sharp
borders.
Sinusoidal gratings
are used because
they are not subject to
defocus,
aberration,diffraction,
light scatter.
 Only the contrast and
spatial position are
affected.

17. Square wave gratings
square-wave
gratings have
characteristics like
a square such as
sharp edges.

18. POSITION OF GRATINGS

19. TYPES OF CONTRAST SENSITIVITY:
1. Spatial contrast sensitivity
2. temporal contrast sensitivity

20. SPATIAL CONTRAST SENSITIVITY
Detection of striped pattern at various levels of
contrast and spatial frequency.
Sine wave gratings of parallel light and dark
bands.
Measured with stationary gratings
width of the bar is defined as spatial frequency
High spatial frequency- narrow bars.
low spatial frequency- wide bars.

21.  The spatial frequency
increases
exponentially from left
to right. The contrast
also varies
logarithmically from
100% at the bottom to
about 0.5% at the top

22. TEMPORAL CONTRAST SENSITIVITY
Temporal contrast sensitivity is measured with
gratings that reverse contrast at various rates over
time.
 here contrast sensitivity function is generated
for the time related processing in the visual
system by presenting a uniform target field
modulated sinusoidal in time.
Both the system provides more complete and
systemic data on the status of visual
performance.

23. The shape of the contrast sensitivity function
varies with factors:
Luminance
Target size
Grating motion
Grating shape

24. Neural mechanism of contrast
sensitivity:
Campbell and Green gave the concepts of
different visual channels for handling
information about bands of spatial frequencies.
 This concept indicates that the retina is not
uniform.
Fovea is specialized for high acuity and is
responsible for high spatial frequencies.
 In the retinal periphery, only low frequency
channels are represented.

25. M and P------- pathways
Ganglion cells divded into
p- Cells :- small,slow
conducting axons that input
into parvocellular layers of
the lateral geniculate body.
P-Cells have higher spatial
resolution.
m-Cells :- large ,fast
conducting axons that input
into the magnocellular layers.
M- Cells have higher contrast
sensitivity and temporal
resolution and lower spatial
resolution.

26. Channel theory
CSF is a function of several independent parallel
detecting mechanisms.
Each channel is highly sensitive to some particular
spatial frequency
 Visual world is broken into its separate spatial
frequency components and this information is then
passed in separate channels to the cortex,where it
reconstructed.
Visual system consists of 4 to 6 spatial frequency
channels

27. Channels
CSF channel could be due to a series of ganglion
cells that have receptive fields of different sizes so
that they are maximally sensitive to different spatial
frequencies.
Stimuli smaller than the center receptive field only
produce a partial response from the ganglion cell.
Stimuli larger than the center receptive field also
stimulate the surrounding area so that the overall
response from ganglion cell is reduced.

28. SYMPTOMS OF CONTRAST SENSITIVITY
Have problems with night
driving, including inability to
see traffic lights
May require extra light to read
Their eyes may become tired
when they read or watch
television
 Not being able to see spots on
clothes, counters, or dishes
Missing facial gestures

29. MEASUREMENT OF CONTRAST SENSITIVITY:
There are three variables in measurement of
contrast sensitivity:
1. Average amount of light reflected depends on
illumination of paper and darkness of ink.
2.Degree of blackness in relation to white
background that is contrast.
3. The distance between the grating periods of
cycles per degree of visual angle.

30. The various methods available to measure CS
include
 Pelli Robson test
 Bailey Lovie chart
 Vision contrast test system (VCTS) by Vistech
 Cambridge low contrast grating
 Regan charts
 FACT charts

31. PELLI ROBSON CONTRAST SENSITIVITY
CHARTS
letters of the same
size but with
reducing contrast
two charts and two
scoring pads.
Each chart has 6
letters in each row
organized into two
triplets of varying
contrast.
illumination of the
chart is 85 cd/mm2
1 meter distance

32. The score of the
test is recorded by
the faintest triplet
out of which at
least 2 letters are
correctly
identified.
The log CS value
for this triplet is
given by the
number on the
scoring pad.

33. CAMBRIDGE LOW CONTRAST GRATING
 It is a rapid and simple screening test for
contrast sensitivity.
 Performed at a distance of 6m.
 It comprises of 12 pair of plates consisting of
stripes of varying contrast.
 First one is for demonstration and rest are for
the proper testing and are numbered from 1-10.

34. The plates are changed sequentially starting
from plate 1 till the patient fails to respond.
Then a new series is begun starting 4 plates
prior to where the patient failed to respond.
Four such series are completed and the score
of each series is noted (numbered as per the
number of plate read) and added.
The final total value is converted into contrast
sensitivity from the provided table.

36. BAILEY LOVIE CHART
Low contrast acuity testing & acuity testing in
presence of glare.
Each row has same no. of symbols & constant
spacing is used between rows & letters.
Chart is logarithmic based & visual acuity is based
on log of minimum angle of resolution or logMAR.
Berkely Glare Test provides 10% of contrast & is
provided with glare source

38. FUNCTIONAL ACUITY CONTRAST
TESTING(F.A.C.T)
FACT charts were developed by Dr. Arthur
Ginsburg.
FACT comprises of a chart with sine-wave gratings
of varying frequencies.
The chart tests five spatial frequencies (sizes) and
nine levels of contrast
The Contrast varies in a row, decrease from left to
right

39. And the spatial frequencies increase as one
move down the various columns from top to
bottom.
This test is performed at a distance of 10 feet.
The patient determines the last grating seen for
each row (A, B, C, D and E) and reports the
orientation of the grating: right, up or left.
The last correct grating seen for each spatial
frequency is plotted on a contrast sensitivity
curve.

41. THE ARDEN PLATE TEST
Introduced in 1978.
Consists of a booklet
containing several sine
wave gratings patterns
Each grating is oriented
vertically
The contrast varies from the
top to the bottom of the
grating, lowest at the top
and highest at the bottom.

42. VISTECH CONTRAST SENSITIVITY TEST
These charts consist of sine wave gratings.
Each chart contains five rows and nine columns
of circular photographic plates (disc) on gray
background.
Each row has different spatial frequency (1.5 to
18 c.p.d. at three meters) and contrast within
the row reduces from left to right.
The gratings are presented in three
orientations: vertical 90 degrees, 15 degrees
clockwise or anticlockwise.

44. Two separate Vistech charts are available: the
VCTS-6500 for distance testing and the VCTS-
6000 for near testing.
A projector slide the VCTS-500S is also
available.
 A luminance of between 103 and 240cd/m2 is
recommended.
 It can be used to document the performance of
low vision patients.

45. REGAN LOW CONTRAST LETTER CHARTS
Consists of three letter charts, printed on white
cardboard having contrast of 97%, 7% and 4%
3 meter with eight letters in each line
Patients are instructed to start at the top and to
continue reading until they can correctly identify
no letters on a line.
For one chart letter size goes on reducing and
contrast remains constant
Regan in 1988 suggested there chief role in
detecting early visual loss in diabetes and
glaucoma.

47. It is widely used in the world
This test provides four rows
of sine-wave gratings
The test distant 2.5 meters,
these gratings test the
spatial frequencies of
3,7,12,and 18 cycles/degree
Good for evaluation eye
disease

48. Use for screening refractive surgery patients

49. Used for in or out of office screening and for
cataract evaluation

50. Used to evaluate both contrast sensitivity and
low contrast acuity
Contain 3 contrast levels

51. Provided the same tests as standard CSV-
1000-S expect that acuity is presented in
landolt c format
Useful when patient cant read English
alphabet

52. It is special test designed specifically for food
and drug administration clinical trials

53. FACTORS AFFECTING CONTRAST
SENSITIVITY
1. refractive errors.
2. age
3.cataract
4.contact lenses
5.refractive surgery.
6.glaucoma.
7.diabetic retinopathy.
8.optic neruopathies
9.pituitary adenoma.
10.drugs.
11.toxic chemicals

54. Refractive errors:
Uncorrected refractive disorders manifest
themselves as a decline in contrast sensitivity
first at smaller grating sizes or higher spatial
frequencies for mild refractive disorders.
 As the degree of refractive disorder increases,
contrast sensitivity declines at the middle and
then larger grating sizes (middle to lower spatial
frequencies).

55. STUDY
 Measurements were made at distance (with
Vistech charts), at near (with Arden gratings),
and with a pinhole to control pupil size.
 Under all conditions, when visual acuity was
reduced by spherical lenses, there was a loss of
contrast sensitivity over a broad range of spatial
frequencies.
Ophthalmology 1988 Jan;95(1):139-43.
Eeffectof visual blur on contrast sensitivity. Clinical
implication
Marmor MF, Gawande A

56. Age:
There occurs a definite decrease in contrast
sensitivity with increasing age.
 The pathogenesis of this decline in vision is
likely involves changes in the spherical
aberration of the crystalline lens

57. As the aperture of lens increases the average
focal point move towards the lens so that a
larger pupil produces greater spherical
aberration
 Spherical aberration of cornea changes little
with the age of the people.

58. Total wavefront aberration of the eye increases
more than threefold, between 20 to 70 years of
age.
 the aging lens loses its balance with the
cornea, because both the magnitude and sign of
its spherical aberration change significantly.
A loss of balance between corneal and
lenticular spherical aberration causes the
degradation of optical quality in the aging eye.

60. STUDY
Monocular and binocular contrast sensitivity
function for a range of spatial frequencies was
measured in two groups of subjects with normal
vision.
 In the age range 50-87 years there was a linear
decline in contrast sensitivity with age for
medium and high spatial frequencies, but
sensitivity for low spatial frequencies was
independent of age.
Effect of age on contrast sensitivity function: uniocular and
binocular findings
 J E Ross D D Clarke and A J Bron.

61. Cataract:
Early cataracts generally cause contrast
sensitivity losses similar to refractive disorders
at higher spatial frequencies.
The addition of glare source will exacerbate the
results for patients with cataract, producing
lower contrast sensitivity at some or all grating
sizes

62. STUDY
significant loss of contrast sensitivity at all
spatial frequencies with increasing cataract
severity. Contrast sensitivity was significantly
reduced at high spatial frequency (18 cpd) in
cortical cataracts in the presence of glare in day
light and at low spatial frequency (3 cpd) in night
light.
Contrast sensitivity scores may offer additional
information over standard VA tests in patients
with early age-related cataracts.

 Ophthalmic Vis Res. 2011 January; 6(1): 26–31.
 Effect of Cataract Type and Severity on Visual Acuity and Contrast
Sensitivity
Javad Heravian Shandiz MSc, PhD,1
Akbar Derakhshan MD,2

63. Contact lenses:
to ensure proper contact lens fit as well as
determining when replacement is necessary.
Uncorrected residual astigmatism from soft
contact lens can result in decrease contrast
sensitivity at the middle and higher spatial
frequencies when compared to hard contact
lenses.

64. study concluded that those female professional
and collegiate tennis players wearing no
corrective lenses were significantly higher in CS
at intermittent and high spatial frequencies than
those who wore daily-wear soft contact lenses
in competition.
Kluka, D.A. and Love, P.A. “Effects of Daily – Wear Contact Lenses Upon
Contrast Sensitivity in Selected Professional and Collegiate Female Tennis
Players,” UBA at Birmingham

65. STUDY
Glaucoma: Glaucoma can reduce contrast
sensitivity for all grating sizes, a number of studies
shown reduce contrast sensitivity mostly at the
middle spatial frequencies.
 study was carried out to explore the effects of
glaucoma on low-spatial-frequency contrast
sensitivity by using tests designed to assess
performance of either the magnocellular (M) or
parvocellular (P) visual pathways. Sensitivity was
reduced foveally and in the midperiphery across the
spatial frequency range. In the area of early visual
field loss, the glaucoma group demonstrated further
sensitivity reduction across the spatial frequency
range.

66. The low-spatial-frequency-sensitive channels of
both pathways, which are presumably mediated
by cells with larger receptive fields, are
approximately equivalently impaired in
glaucoma.
 Contrast sensitivity changes due to glaucoma and normal aging: low-spatial-
frequency losses in both magnocellular and parvocellular pathways.
 McKendrick AM Sampson GP, Walland MJ, Badcock DR
 Invest Ophthalmol Vis Sci.2007 May;48(5):2115-22

67. STUDY
IOLs
A study was carried out to evaluate the contrast
sensitivity at near and distance after MFIOL
implantation in 21 patients. A control group with
monofocal iol was also studied. CS measured
after 1,3,6,12,and 18 months after IOL.

68. CONTRAST
SENSITIVITY
MULTIFOCAL MONOFOCAL
CONTRAST
SENSITIVITY AT
DISTANCE(1 MONTH)
(3 MONTHS)
(6, 12 AND 18)
CONTRAST
SENSITIVITY AT NEAR
L Cataract refractive surgery.2003apr;29(4):703-11
Montes mico R

69. MONOFOCAL
(ALCON
ACRYSOF)
ACCOMOD
ATING
(HUMAN
OPTICS)
DIFFRACTIVE
MFIOL
(TECNIS)
REFRACTIVE
MFIOL
(AMO
REZOOM)
NEAR
VISUAL
ACUITY
- - BETTER -
DIST. CS HIGH HIGH - LOW
NEAR CS
HIGH SF
MONOCUL
AR AND
BINOCULAR
CS
HIGH
HIGH
HIGH
HIGH
HIGH
LOW
LOW
LOW

70. multifocal In patients with unilateral cataract,
monofocal, accommodating and partially diffractive
multifocal IOL provided higher CS scores when
compared with refractive IOL.
Clinical and experimental ophthalmology
Differences in contrast sensitivity between monofocal,
multifocal and
accommodatingintraocular lenses: long-term results
Cem Mesci MD, Hasan H Erbil MD, Ali Olgun MD, Nihat Aydin MD,
Article first published online: 3 NOV 2010 DOI: 10.1111/j.1442-
9071.2010.02357.

71. Diabetic retinopathy:
In diabetic retinopathy patients, contrast
sensitivity loss may occur for all grating sizes.
a study was carried out to evaluate contrast
sensitivity (CS) and visual acuity (VA) in
detecting functional losses in participants with
type 2 diabetes.
LogMAR VA and letter CS were measured on 20
type 2 diabetic and 24 age-matched control
participants. The diabetic participants were
sub-grouped according to the level of
retinopathy present.

72. RESULTS:
Letter CS was able to distinguish those
participants with and without macular oedema
and those with no or minimal diabetic
retinopathy from the control group, whereas VA
was not.
Clinical optom 2003 May;86(3):152-6
Letter contrast sensitivity changes in early diabetic retinopathy
Stavrou EP, Wood JM

73. Optic neuropathies:
A variety of optic neuropathies including
afferent pupillary defect, optic neuritis, and
multiple sclerosis will affect contrast sensitivity
losses over some or all grating sizes.
Multiple sclerosis can sometimes affect only
middle sizes.

74. Pituitary adenoma:
Pituitary adenoma has been shown to cause
contrast sensitivity loss at the middle grating
sizes.

75. STUDY
Cases report was made by
neuroophthalmological examination in two
patients with parasellar pituitary adenoma
before and after surgery.
The twelve months follow-up of visual
dysfunction includes standard Snellen visual
acuity and low contrast number visual acuity.

76. The presented cases indicate that the low
contrast acuity tests in patients with parasellar
pituitary adenoma are sensitive indicators.
The loss of low contrast visual acuity improved
after surgery as did other visual measures,
except in cases with significant low contrast
deficit at 1.5% contrast.
Kruzer, A.R. (1986) “ Contrast Sensitivity Signals Pitutary Adenoma,” Rev. Of.Opt.
123(4), 119

77. Toxic Chemicals:
Several occupational studies have indicated
that chronic, airborne exposure adversely
affects neurobehavioral functions in workers,
particularly visual color discrimination and
tasks dependent on rapid visual-information
processing
Frenette, B.,Mergler, D. And Bowler, R.(1991) “Contrast Sensitivity Loss in Group of
Former
Microelectronics Workers with Normal Visual Acuity,” Opt. and Sci.,68(7),.

78. CONTRAST SENSTIVITY AND LASIK
Why refractive surgery can affect the quality of
vision.
there are other factors in the eye, which affect
vision quality, that are unrelated to eye focus.
These factors can cause the quality of vision to
vary greatly, even when a patient has 20/20 or
better acuity. Contrast sensitivity is the best
method for quantifying the quality of vision

79. Examples of the change in contrast sensitivity
with lasik refractive surgery:
The graphs show the pretreatment level of
contrast sensitivity (with the patient wearing his
or her glasses) and the contrast sensitivity after
1 day, 1 week and 1 month of surgery (with the
patient wearing the best correction).

82. the patient contrast sensitivity does not recover to the
presurgery levels. The following graph shows an
example of this response in vision quality

83. Several surgeons have noted that some patients with high levels
of myopia (> - 9 diopters) actually improve contrast sensitivity
after LASIK surgery. The graph below shows an example. The
reason for this improvement in the quality of vision is not
completely understood, but it is thought to be due to the poor
quality of vision that some patients have through their glasses or
contact lenses before LASIK.

84. Low contrast acuity after lasik

85. glare testing, which shines a bright light in the
patient's eye, reduces pupil size and typically causes
vision to improve. The graph below shows the results
of a patient tested for contrast sensitivity in darkness
and then again with glare. the glare condition
dramatically improves the contrast sensitivity

86. With glare, the yellow filter also improved
contrast sensitivity in LASIK patients, but not
significantly.
J Refract surgery2005 Mar-Apr;21(2):158-65.
Effect of a yellow filter on contrast sensitivity and disability glare after laser in
situ keratomileusis under mesopic and photopic conditions.
Pérez-Carrasco MJ, Puell MC, Sánchez-Ramos C, López-Castro A, Langa A.