Contrast sensitivity refers to the ability to see objects that have low contrasts or do not stand out clearly from their backgrounds. It is measured using charts with different spatial frequencies and contrast levels to determine the minimum contrast needed to see a target. Contrast sensitivity is affected by many eye diseases and conditions more subtly than visual acuity and can provide early detection of problems. It is tested using various charts like Pelli-Robson, Cambridge Low Contrast Gratings, and Functional Acuity Contrast Testing (FACT) that evaluate contrast sensitivity levels at different spatial frequencies.

1. Contrast
sensitivity
Jagdish Dukre

2. What is contrast sensitivity ?
 Visual ability to see object that may not be
outlined clearly or not stand out from their
background.
 The ability to see a shade of gray on white
background or to see white on light gray
background.

3. Contrast sensitivity
 Contrast Def.
The difference in the luminance of target
against the background.
 contrast
target luminance – background luminance
target luminance + background luminance

4. Contrast threshold
 The minimum resolvable contrast.
 It described in logarithmic terms.

5. Contrast sensitivity function
 The manner in which contrast sensitivity
changes as function of spatial frequency of
the target .
 Contrast sensitivity can be tested with sine
wave grating using either charts or video
gratings or
 with opto types of variable contrast such as
pelli-robson or regan chart.

6. How is c.s different than acuity :-
 CS is unlike acuity , c.s measures tow
variable size & contrast while acuity
measures only size.
 CS measure the degree to which this ability
has been lost , while snellen visual acuity
measures the ability to see object of different
size.
 Snellen chart useful for describing changes
in vision caused by spherical blur but unable
to detect many types of vision loss are not
cased by spherical blur.

7. Compare:
E
smaller
E
Letter Size Spatial Frequency
higher

9.  Some patient can have normal visual acuity
& reduced c.s such as those with
1. Optic neuritis .
2. Multiple sclerosis
3. Parkinson’s disease
4. Papilloedema
5. Primary open angel glaucoma
6. Diabetic retinopathy
7. Compressive lesions of visual pathways

10. Benefits of c.s testing
 early detection of serious eye diseases, It also helps in more
accurate monitoring of ocular conditions
 Contrast sensitivity testing complements the traditional 20/20 visual
acuity value by measuring more subtle vision losses due to
problems with spectacle lenses and contact lenses.
 It also offers important information in the fitting of contact lens
 Contrast sensitivity testing assists in more precise assessments of
patients prior to surgery and post-operatively.

11. Sinusoidal gratings
 The most commonly used stimuli for
assessing the contrast sensitivity
characteristics of the human visual
system are sinusoidal gratings,
consisting of an alternating pattern of
light and dark bars whose luminance
varies sinusoidally in the direction
perpendicular to the grating's
orientation.

12. The Physical Stimulus: Spatial pattern
photometer

13.  The appearance of a sinusoidal grating is an
alternating series of fuzzy light and dark lines.
 The size of the light and dark bars of the grating is
specified according to spatial frequency, which is the
number of cycles (pairs of light and dark bars) of the
grating pattern per degree of visual angle.
 Typically, the range of spatial frequencies examined is
between 0.5 and 30 cycles per degree.
 The contrast of the sinusoidal grating is determined by
the luminance of the peaks (Lmax) and troughs (Lmin) of
the luminance profile

14. 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.

15. Seeing your own CSF
Contrast
Spatial Frequency

16. Low spatial frequency High
High contrast Low
THE
CONTRAST
SENSITIVITY
FUNCTION

19. Brightness Perception

22. What are symptoms of low c.s?
 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

23. CONTRAST SENSITIVITY
TESTING
 It will be done while you wear your eye
glasses or contact lenses if you require
vision correction
 Testing done with both eye together to
determine ability to see low contrast object
 For evaluation of eye disease contrast
sensitivity contrast sensitivity is tested on
each eye individually .

24. Contrast sensitivity
 Contrast sensitivity measured at normal
room illumination which about 30-70
footlamberts
 Luminance must be kept constant when
contrast sensitivity tested because mean
luminance has an effect on the shape at
normal contrast sensitivity function

25. Conditions affects cs
 Pupil size has effect on contrast sensitivity as it does on
snellen acuity
 miotic pupils =diffraction reduce contrast sensitivity
 Dilated pupils leads to optical aberration
 Contrast sensitivity can also be affected by a distortion or
edema.
 Lens changes due cataract leads to decrease contrast
sensitivity.
 Retinal pathology may affect contrast sensitivity.
 Retinitis pigmentosa.
 Central serous retinopathy.
 Macular degeneration.
 Glaucoma.
 Retrobulber optic neuritis.
 Amblyopia.

26. Pelli-robson letter contrast
sensitivity
 It is simply of quickly measured and provides a
reliable measurement of low spatial frequency
contrast sensitivity ( 0.5 – 2 cycles)
Method:
 Sit the patient 1m from the chart with his or her
correction if needs
Occlude one eye or with both eye
 With both eyes result high with 0.15 log units
Asked patient to read lowest letter that can see

27. Pelli-robson letter contrast
sensitivity

28. Record the contrast sensitivity score in log
units
Results:
For patient 20-50 years old monocular
contrast sensitivity should be 1.80 log unit
Patient less than 20 years and older so
years =1.65 log units

29. Most common errors
 Not allowing patient at least 20 second
for letters to become visible
 Not pushing patient to guess
 Illumination is poor

30. Cambridge low contrast
gratings
 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.
 The plates are changed sequentially
starting from plate 1 till the patient fails to
respond.

31. Cambridge low contrast
gratings
 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.

32. Functional Acuity Contrast Testing
(FACT)
 FACT charts were developed by Dr. Arthur
Ginsburg.
 FACT comprises of a chart with sine-wave
gratings of varying contrast as well as
varying spatial frequencies.
 It is an accurate and comprehensive
grating chart that tests functional visual
acuity.
 This test is performed at a distance of 10
feet.

33.  The chart tests five spatial frequencies (sizes) and nine levels of
contrast.
 The Contrast varies in a row, decrease from left to right.
 And the spatial frequencies increase as one move down the
various columns from top to bottom
 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.