This document provides an overview of low vision assessment techniques. It outlines the underlying philosophy of assessing the psychosocial impact of visual impairment and the stages of grief patients may experience. The document then details the typical steps in a low vision assessment, including observation, patient history, visual acuity testing, refraction, tests of binocularity, visual fields, contrast sensitivity, color vision, and illumination needs. It provides information on techniques for visual acuity testing, refraction, and monitoring follow-up care. The goal of low vision assessment is to understand the patient's needs and vision abilities in order to provide optical and non-optical devices and training to improve their quality of life.

1. An Overview of Assessment
Techniques in Low Vision
Dr. John Dean
Low Vision Practitioner

2. ➢ Impact of Visual Imparment
➢ Underlying philosophy of Low
Vision Assessment
➢ Steps in Low Vision Assessment
OUTLINE

3. Consequences for individuals
Low
Vision
Patient
Economic
Educational
Social
Physical
Emotional
Behavior
QUALITY
OF LIFE

4. Psychosocial Impact of Visual Impairment
● Stages of Grief:
1. Shock and Denial
2. Guilt and pain
3. Anger and bargaining
4. Depression, Loneliness and Reflection
5. The Upward Turn
https://www.betterhelp.com/advice/grief/understanding-the-stages-of-grief/

5. Low Vision Assessment
Underlying philosophy
The provision of low vision care for children needs to
be integrated within eye care and
education/rehabilitation services, and it needs to be
accessible to all children.

6. Steps in Low Vision Assessment
● Observation
● Patient History
● Visual acuity: near and
distance
● Refraction and prescription
of distance spectacles
● Binocularity
● Visual field
● Contrast sensitivity
● Color vision
● Illumination
● Prescription and training of
optical low vision devices
● Advice on non-optical
devices
● Referral

7. Observation
● Observing the client’s behavior and his physical status
gives an information to the severity of the problem.
● Areas to be observed:
○ Postural abnormalities: Head turns/tilts
■ Towards the side of field loss
■ To find the null point of nystagmus

8. Observation
● Areas to be observed:
○ Fixation: eccentric fixation in central scotoma
○ Mobility: speed, accuracy, confidence, with support
○ Appearance: general, clothing, sunglasses, squeezing of eyes
○ Psychological behavior: depressed, angry, lack of confidence,
expectant
○ Other disabilities: LD, Down syndrome

9. Patient History
● Problems and vision related needs
● Components:
○ General information: Personal,
family, medical history
○ Ocular history: Onset,
Prognosis, Duration, Stability,
Medical history
○ Motivation and expectation
○ Visual performance (task
related)
○ Previous low vision assessment
○ Use of any devices
○ Visual goals

10. Ocular Health Examination
● Slit-lamp biomicroscopy
● Ophthalmoscopy
● Light and magnifier

11. Visual Acuity
● Take note of the following:
○ Age
○ Literacy
○ Learning ability
○ Simplicity
○ Familiarity
● Children: Match, Point, Name

12. Visual Acuity: Distance

13. Visual Acuity: Distance

14. Visual Acuity: Distance
Test Purpose Appropriate/Intended Population
1. Snellen To determine distance visual acuity
Test Distance: 20 ft/6m
2. Bailey-Lovie To determine distance visual acuity
Test Distance: 4m
Individuals who can match or verbalize alphabet or numeric
symbols
3. HOTV To determine distance visual acuity
Test Distance: 3m
Children who are 3 years old or older
4. LEA Symbols
(Single-symbol)
To determine distance visual acuity
Test Distance: 3m
Young children who can match or verbalize symbols
Those who cannot perform in line-test situations
5. Feinbloom To determine distance visual acuity
Test Distance: 3m
Children who can accurately discriminate letters and numerals;
youth and adults; those with very low vision who need larger
optotypes
6. LEA Gratings To determine resolution acuity at
near and intermediate distance
Test distance: 115cm, 85cm, 57cm,
43cm, 28cm
Individuals who are infants or toddlers or who are unable to
respond to symbol acuity charts

15. Visual Acuity: Testing
1. 4m>3m>2m>1m>0.5m
2. Use bigger chart 3m>2m>1m>0.5m
3. Light Projection
4. Light Perception
5. NLP

16. Visual Acuity: Recording
● M-notation or M-unit
● Distance/Optotype(size)
● Examples:
○ Distance: 4m/40M

17. Visual Acuity: Near

19. Visual Acuity: Recording
● M-notation
● Ex: 8M @ 40cm

20. Refraction
● A careful refraction is needed
● It can improve distance and near vision

21. Refraction
● Subjective refraction is always needed especially when retinoscopy gives no
good result.
● Bracketing technique - is a procedure used in subjective refraction in which
large and equal steps of dioptric changes are made above and below the
presumed correct answer, and then reducing the size of the dioptric changes
and shifting the center of the range, until the finest and just detectable blur is
induced by equal steps above and below the refractive error.
Click to add text

22. Bracketing Technique
→ JND – Just Noticeable Difference
Fundamentals of Bracketing:
• Embrace: Things are better between the two limits, BOTH limiting lenses
should be rejected
• Diffferential responses:
• “shades of certainty” judged by response speed, tone, or words
• Depend on the patient’s discrimination abilities and size of differences between comparisons
• Progressively reduce size of bracket: from each bracketing, estimate the final
answer. The next bracket should embrace your current best estimate of the
answer

23. Binocular Vision
● Tests:
1. Lang Two Pencil Test
2. Maddox Rod
3. Sterofly

24. Visual Field Test

25. Contrast Sensitivity
● Hiding Heidi
● Lea Symbols
● Lea Numbers
● Mars Perceptrix Test

26. Color Vision

27. Lighting/Illumination
● Room illumination
● Day
● Night
● Task illumination

28. Monitoring/Follow-up
● To identify success:
○ Can the client to the tasks they want to do?
○ Are they using the spectacles/low vision device?
● To identify any new problems
● To adapt the distance correction
● To adapt the magnification/non-optical devices

29. Any questions???