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 = 1.0M –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