LOW VISIONLOW VISIONAnne L. Corn, Ed.D.Vanderbilt UniversityLow VisionLow Vision How do we know when vision is workingwell?DefinitionsDefinitions Blindness Functional Blindness Legal Blindness Low Vision Partially Sighted Visual ImpairmentDefinitionsDefinitions Other terms– Residual Vision– Visual Loss– Remaining VisionDefinitionsDefinitions What is blindness? What do blind people see? Is there a continuum of visual abilities? Is blindness an impairment, a disability,nad/or a handicap?Types of Low VisionTypes of Low Vision Low visual acuity– With clear ocularmedia– With cloudy ocularmedia or cornia– With central scotoma– Without scotomaMeasuring Visual AcuityMeasuring Visual Acuity Snellen Chart Low Vision Charts Objects at various distances Rolling balls Preferential Looking TestMeasuring Visual AcuityMeasuring Visual Acuity Use of Measures– Meaning of measures– Interpretation of measures– Measures for eligibility for servicesTypes of Low VisionTypes of Low Vision Visual fieldrestrictions– Central– Peripheral– Multiple scotomas– Hemianopsia– Retinal tears– Lack of regardTypes of Low VisionTypes of Low Vision Low Contrast Sensitivity Illumination– Photophobia– Need for more light– Glare Eye Movement Disorders, e.g., Nystagmus Cortical Visual ImpairmentsTypes of Low VisionTypes of Low Vision Combined Types Other (alone do not cause low vision)– Monocular vision– Color deficiencies– Strabismus– Visual perceptual disorders.PERCENTAGE OF U.S. POPULATIONBY AGE CATEGORY75 – 8465 – 7445 – 645 – 1920 – 440 – 4Low VisionBlind85 +3020100Clinical MeasuresClinical Measures Low Vision AcuityCharts Low Vision ColorTests Low Vision ContrastSensitivity ChartsFunctional MeasuresFunctional Measures Functional VisionAssessment Learning MediaAssessment Orientation andMobility AssessmentExpectations for VisualExpectations for VisualFunctioningFunctioning Meet John:– O.U. 20/200– Age 21– Oculocutaneous albinism– Average IQ– Efficient user of optical devicesExpectations for VisualExpectations for VisualFunctioningFunctioning How many of you believe John is able to:– Read a paperback novel (Star Trek)?– Read a street sign from across the street?– Read for an hour at a time?– Read a menu at a fast food restaurant?– Drive a car?Myths of Low VisionMyths of Low Vision People with low vision only see a few feetin front of them. People with low vision will harm their eyesif they are used. People with low vision see blurry images All people with low vision need large print.Myths of Low VisionMyths of Low Vision People with low vision are old people. People with low vision should learn how tofunction as blind people. People with low vision are “faking it” People with low vision should only learn touse their vision.Models of Visual FunctioningModels of Visual Functioning Corn (1983)– Model of VisualFunctioning Congenital AdvenitiousModels of Visual FunctioningModels of Visual Functioning Visual AbilitiesDomainModels of Visual FunctioningModels of Visual Functioning Environmental CuesDomainModels of Visual FunctioningModels of Visual Functioning Stored and AvailableIndividuality DomainModels of Visual FunctioningModels of Visual Functioning Hall and Bailey, 1989– Visual Behaviors: A Modelfor Training VisualFunctioning– VISUAL CAPACITIES– VISUAL ATTENDING– VISUAL EXAMININGBEHAVIORS– VISUAL GUIDINGBHEAVIORSInterventionsInterventions Optical Devices Non Optical Devices Environmental Modifications TechniquesInterventionsInterventions Low Visual Acuity – expand retinal image– Magnifiers Telemicroscopes– Monoculars Bioptic Systems– Closed Circuit TV Software– Reduce distance Visual Fields– Central – magnification, eccentric fixation– Peripheral – prisms, reversed telescopes, eye scanningInterventionsInterventions Contrast Sensitivity– Filters Illumination– More illumination– Reduced illumination – non optical devices, therapeuticcontact lenses Non Visual Approaches– Combined with visual– Non visual learning – tactual, auditoryMajor Research QuestionsMajor Research Questions What differences exist in the clinicalmeasures and functional abilities of normaland low vision populations?– Are there differences in how children with andwithout low vision use their peripheral vision?– Are there differences in reading fluency ofadults of with congenital and adventitious lowvision who have similar clinical measures?Major Research QuestionsMajor Research Questions What relationships exist between thepathology, clinical measures and functionalabilities?– At what stage of diabetic retinopathy dofunctional limitations begin to impact mobility?– Are there differences in the patterns of visualattention for students with Stargardt’s Diseaseand those with Leber’s Disease?Major Research QuestionsMajor Research Questions What interventions are effective in increasingfunctional visual abilities?– What impact does the use of individually prescribedoptical devices have on the reading fluency of studentswith low vision?– Does training in the use of peripheral vision result infewer impact incidents of adults with acquired lowvisual acuity?– Does teaching eccentric fixation improve reading ratesof those with acquired central scotomas?Major Research QuestionsMajor Research Questions In what ways does low vision impactchildren’s and adults’ lifestyles?– What is the impact of oculocutaneous albinismon African-American teenagers with albinism?– How do the employment rates and earnings ofyoung adults with low vision 3-5 years out ofschool compare with those of students withother disabilities and with those withoutdisabilities?Multidiscipinary Multidiscipinary ApproachesApproaches Ophthalmologist Optometrist Clinical low vision specialist Teacher of students with visual impairments Orientation and mobility instructor Rehabilitation teacherProviding Access to the VisualProviding Access to the VisualEnvironmentEnvironment Project PAVE– Multidisciplinary– Direct Service– Consultation– Continuing Education– ResearchProject PAVEProject PAVE Clinical low visionevaluationsProject PAVEProject PAVE Instruction in visualefficiencyProject PAVEProject PAVE Instruction in the useof optical