1. The document discusses various clinical tests used to assess contrast sensitivity and glare, including contrast threshold, contrast sensitivity function, and different contrast sensitivity charts. 2. It explains the significance of measuring contrast sensitivity to detect abnormal visual performance, diagnose ocular diseases, and monitor disease states. Reduced contrast sensitivity can occur in conditions like amblyopia, cataracts, and glaucoma even when visual acuity is normal. 3. Methods for testing glare are described, along with their use in assessing conditions involving the cornea and lens, both before and after surgery. Various glare testing devices quantify the effects of light scatter on vision.

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