LET’S TALK
LOW VISION
Suleiman Alibhai, O.D.
Retina Group of Washington
Krista M. Davis, O.D., F.A.A.O.
Columbia Lighthouse for the Blind
Eye Anatomy
Definitions
Legal Blindness
– Best corrected distance visual acuity of 20/200 or
worse in better eye
– Horizontal visual field of 20 degrees or less at widest
point in the better eye
Low Vision
– Worse than 20/60 in the better eye
– Significant field loss
– Impaired function
Goals of Low Vision
Management
Increase functionality
– Make the most of the remaining
vision
Provide link to community
resources and support services
Education
Common Conditions
 Macular Degeneration
 Albinism
 Glaucoma
 Nystagmus
 Diabetic Retinopathy
 Cortical Visual
Impairment
 Stroke/ brain injury
 Retinitis pigmentosa
 Optic Nerve disease
Functional Effects of
Low Vision
Loss of central vision (visual
acuity)
Loss of peripheral vision
(visual field)
Glare and contrast
Issues Related to
Decreased Acuity
Difficulty reading
Problems writing/ completing
paperwork
Inability to recognize
distance objects and faces
Issues Related to
Visual Field Loss
Location of scotoma important!
Generalized loss of visual field
difficult to compensate for
Mobility and independent travel
Reading may require adaptations
Issues Related to Contrast
Need for additional lighting
Problems with glare
Increased adjustment to changes in
illumination
Visual discomfort and fatigue
Exam Sequence
 History/ intake
 Visual acuity
 Visual field testing
 Pupils
 Extraocular muscle testing
 Refraction
 Color vision and Contrast Testing
 Ocular Health
Types of Acuity Charts
Distance
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–
–
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Snellen (projection)
Feinbloom/ SOSH
ETDRS
Lea Symbols
Near
– Single letter
– Continuous text
Distance Charts
Near Charts
Interpreting Near Acuity
Threshold acuity
– Difference between single letter and continuous
text
1.0 M = 20/50 = 8-10 point font
– Need to look at working distance
– Jaeger charts nonstandard
Typical sizes
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–
–
–
Newspaper = 1.0M
Children’s books = 1.2 – 1.6M
Large print = 1.6 – 2.0M
Newspaper headlines = 4.0 – 5.0 M
Visual Field Testing
Confrontation
Arc perimeter
Vision Disc
Automated perimetry
Goldmann perimetry
Color and Contrast Tests
Ishihara
Color Vision Testing Made Easy
D-15
Pelli-Robson
Vistech Contrast System
Mr. Happy
Hiding Heidi
Color Vision Tests
Contrast Tests
Magnification
Enlarges image on retina to stimulate more
retinal cells
Can be achieved in many ways
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–
–
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Relative Distance
Relative Size
Optical / Angular
Electronic
Low Vision Devices
Distance
Near
Field enhancement
Non-optical
Distance Devices
Hand held telescopes
Mounted telescopes
Electronic systems
Telescopes
Electronic Distance Systems
Near Devices
Spectacles
– Prismatic ½ eyes
– Full-field microscopes
Magnifiers
– Hand held vs. stand
– Illuminated vs. non-illuminated
Telemicroscopes
Electronic Devices
Spectacle Microscope
Near Loupe
Hand Held Magnifiers
Stand Magnifiers
Electronic Magnifiers
Non-optical Devices
Glare reduction devices
Contrast enhancement devices
Computer software
Accessory devices
– Talking watches, clocks, etc
– Writing guides
– Tactile markers
Glare and Contrast
Lighting
Other Non-optical Devices
Adaptive Computer
Equipment
Additional Services
Orientation and mobility training
Independent living skills training
Support groups
Braille instruction
Computer training
Genetic counseling
Community Resources
Support groups
Paratransit Services
Books on tape
Audio described performances
Tactile tours
Large print publications
Educational services
Communication Goals
 Educate patient on eye condition
 Help them to understand what options are
available and how to use/ care for tools
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–
–
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Glasses
Low vision devices
Technology
Community resources
 Educate parents and teachers/ professionals on
functional implications
Functional Implications
Print size
Visual efficiency and fatigue
Mobility issues
Positioning/ classroom placement
Lighting/ glare reduction needs