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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 – – – – 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 = 1.0M 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 – – – – 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
