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 ¬ Glaucoma ¬ Diabetic Retinopathy ¬ Stroke/ brain injury ¬ Retinitis pigmentosa ¬ Optic Nerve disease ¬ Albinism ¬ Nystagmus ¬ Cortical Visual Impairment
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 – 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 – – Newspaper = 1. 0 M Children’s books = 1. 2 – 1. 6 M Large print = 1. 6 – 2. 0 M 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 – 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 – – 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
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