1. Contrast sensitivity, Clinical
assessment of intra-ocular
light scatter, Dark adaptation,
recovery from glare (macular
photo stress test)
Mohammad Arman Bin Aziz
Optometry Officer
ICO, CU
March 20, 2014

2. Contrast
• The ratio of the difference of maximum luminance and
minimum luminance to the sum of max and min luminance
• Contrast /modulation = L max – L min
L max + L min
• E.g. White stimulus in white background, contrast= 0%
• Black in white background = 100 %
• Expressed in percentage
Luminance - The intensity of light per unit area of its source

3. Contrast threshold
• Object with the lowest contrast that a patient can recognize
• The minimum contrast required to be able to see a target.
• Contrast sensitivity : reciprocal of contrast threshold
• CS = 1 / CT
• Increase in CT = Decrease in CS
• An object with the lowest contrast that a patient can recognize.
• Expressed as percentage.
• CS= reciprocal of CT
• Maximum CT = 100%
• CT depends on size of object

4. Contrast sensitivity
Ability to perceive slight
change in luminance
between regions which
are not separated by
definite borders.
Photopic system is more
sensitivity to contrast than
the scotopic system
• Snellen VA measures patients
high frequency cut-off.
• Normal high frequency cut off
= 60 cycles/degree.
• Snellen letter - not represent
visual function in reality.
• Refractive errors – decrease
visual performance at mid &
high SF.
Contrast in VA letters

5. Contrast Sensitivity
•CS measurement for
•To detect abnormal visual performance
•To diagnose ocular disease & monitor its states
•To predict performance on specific visual tasks
•VA normal but CS of low & medium SF decrease in
•Amblyopia, astigmatic error, cataract, diabetes,
glaucoma, keratoconus, multiple sclerosis, ocular
hypertension, optic neuritis & papilledema.

6. Why to measure CS?

7. Contrast Sensitivity Function (CSF)
• Identical Snellen acuities can yield substantially different visual
capabilities
• Predicts the outcome of ophthalmic aids. e.g. the final reading
speed with a magnifying device (Leat & Woodhouse)
• Monitors the course of ocular disorders that result in contrast
sensitivity reduction, such as cataracts or ARM
• Monitors a variety of conditions that result in visual impairment
• E.g. Multiple sclerosis
- Snellen acuity within normal range, hidden losses in the mid
and low spatial frequency domains (Pace & Woo, 1984)

8. Example

9. Contrast sensitivity of
the human eye
Modulation transfer function for a
human eye at various pupil diameters.
Curves for 2.0 and 2.8mm pupils cross over at about 27c/d.

10. Contrast sensitivity Charts
Pelli-Robson Chart
Regan Low Contrast Chart
Bailey Lovie Low Contrast Chart (10%)
University of Waterloo Low Contrast Chart
Cambridge Gratings
Vistech Chart
Lea Low contrast Chart
Melbourne Edge Test
Hieding Hiedi

11. Pelli-Robson chart
Score 2.0 = normal
Score < 1.5 = visual impairment
Score < 1 = visual disability

12. Bailey-Lovie 10% low contrast chart100% contrast chart

13. LEA low contrast chart

14. Vistech chart
• 6 rows
• 3 inch diameter sine wave
gratings
• Each row a sample grating and a
• series of test grating fixed
spatial
• frequency but varying contrast.
• S.F 1, 2,4,8,16,24 c/d
• Vertical ,slanted 15 deg to R, 15
deg to L

15. Melbourne edge test
•Use of boundary between
light and dark background
•20 circular stimuli each
2.5mm in diameter
•Subject shown a key card
vertically, horizontally and
obliquely oriented

16. Hiding heidi
< 5% contrast cannot recognize face

17. Cambridge low-contrast gratings
Square wave gratings
Spatial frequency: 4 c/d
Varying contrast
• Vector vision CSV-1000

18. Addressing Reduced contrast
Needs adequate magnification
felt-tipped pens
good lighting on object or print
bold lined paper
writing guide

19. Types of contrast sensitivity loss
Type 1
CS loss at high frequency
Normal at low frequency
E.g. early cataract, ARMD
Type 2
 CS loss at all spatial
frequency
Type 3
 High frequency CS normal
 Reduced CS at low frequency
e.g. optic neuritis
multiple sclerosis,
POAG,
Papilledema, Diabetes
(Leguire and Regan 1991)

20. Clinical Significance
CS measurement for………..
• To detect abnormal visual performance
• To predict performance on specific visual task
driving ability
good/ disable reading capacity
mobility
face recognition
sports etc.
• Contrast provides critical information about
Edges
borders and
variations in brightness

21. VA normal but CS of low & medium SF decrease
o Amblyopia
o Astigmatic error
o Cataract
o Diabetes
o Glaucoma
o Keratoconus
o Multiple sclerosis
o Ocular hypertension
o optic neuritis
o Papilloedema
o Contact lens wearing Patient

22. Factors Affecting CS
•Age
•Refractive Error
•Lenticular Opacities
•Pupil Size
•Ocular Diseases
•Systemic Diseases
To diagnose ocular disease & monitorTo diagnose ocular disease & monitor
its statesits states
• Predicts the outcome of ophthalmic aids.
e.g. the final reading speed with a
magnifying device
(Leat & Woodhouse)
• Monitors the course of ocular disorders
that result in contrast sensitivity reduction
- cataracts
- ARMD
- RP

23. Ocular Diseases
Glaucoma
 Advanced diabetic retinopathy
Multiple sclerosis
Media opacities
Neurological problem
Cataract
Retinal disease
Optic nerve disease
Retrobulbar neuritis
Corneal edema
Multiple Sclerosis-
DM
Pituitary Adenoma
Systemic diseases

24. Addressing Reduced contrast

25. Cont.

26. CCTV
Adjustable illumination, contrast
& magnification system

27. Glare
• Refers to the presence of one or more
areas in the field of vision that are of
sufficient brightness to cause
discomfort in vision.
• Visual perception created by external
light
• Glare source : Axial / Peripheral
• Reduces the quality of the image
• an unpleasant sensation
• a temporary blurring of vision
• a feeling of ocular fatigue
Classification
• Veiling or disability glare
• Discomfort glare
• Specular reflection glare

28. Veiling or disability glare
Arises from stray light falling on the retina, usually from
scatter by the media of the eye.
Scattered light falls as a patch of veiling illuminance on the
fovea and reduces the contrast of the retinal image.
Reduces the contrast of the retinal image.
Reduces visibility and visual performance.
E.g. sky, sand, brightly illuminated walls etc.- the reflected
images are large in angular sub tense leading to reduction in
contrast observed in the visual field.

29. Glare in Cataract
Normal Cataract

30. Discomfort glare
Occurs when the illumination in a part of the visual field is
much greater than the level of illumination for which the
retina is adapted.
Occurs when the ratio between the highest level of
illumination in the visual field and background illumination
exceeds a ratio of 3 to 1.
An extreme case of glare often occurs during night driving-
causes extreme discomfort.

31. Specular reflection glare
Occurs when patches of bright light are reflected form
smooth, shiny surface into the eye.
Typical reflecting surfaces include expanses of water,
snowfields, roadways etc.
Reflections are not only annoying but interfere with
visibility, at times seriously.
Can be well controlled by using polaroid glasses.

32. Glare testing
• Objective :
• quantify the deleterious effects of light scatter on visual
performance
• Reduce the effect on impairment of vision
• When?
• Corneal opacities
• Corneal dystrophies/ Degeneration
• Cataract

33. Pre& post-operative indications for glare testing
Pre-operative Post-operative
Cornea Cornea
• Infectious scarring -PK
• Traumatic scarring -Epikeratophakia
• Degenerative scarring -Keratomileusis
• Dystrophic scarring -Repaired laceration
Lens Lens
• Age-related cataract -PCO following ECCE,IOL
• Traumatic cataract
• Drug-induced cataract
• Disease-induced cataract

34. Glare Testers
• Instrumentation
• A glare source when
introduced in an eye with
media opacity causes some
degree of visual disability.
• Current glare testing
devices gives this extent of
disability in the form of
reduced contrast
sensitivity or visual acuity.
• Brightness Acuity Tester (BAT)
• Optec 1500 Glare Tester
• Miller-Nadler Glare Tester
• Terry Vision Analyzer (TVA)

35. Assessment of Glare
Brightness Acuity Tester Miller-Nadler Glare Tester

36. Photostress test

37. References
• Clinical procedure of Primary Eye Care
• Clinical Procedure of Optometry
• Internet