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Blindness 101Blindness 101

Kevin Houston, O.D., F.A.A.O.Kevin Houston, O.D., F.A.A.O.

Clinical Assistant ProfessorClinical Assistant Professor

Indiana University School of OptometryIndiana University School of Optometry

kehousto@indiana.edukehousto@indiana.edu

OutlineOutline

Ocular Anatomy (Healthy and diseasedOcular Anatomy (Healthy and diseased

eyes)eyes)

Typical Eye ExamTypical Eye Exam

Reading the Reading the ““eye reporteye report””

Low vision consultationLow vision consultation

Services at IU School of OptometryServices at IU School of Optometry

clinicsclinics

Ocular AnatomyOcular Anatomy

FROM NEI/NIH

1. Cornea1. Cornea

2. Pupil2. Pupil

3. Iris3. Iris

4. Sclera4. Sclera

5. Macula5. Macula6. Optic6. Optic

NerveNerve

7. Arcade7. Arcade

8. Equator8. Equator

Ocular AnatomyOcular Anatomy

FROM NEI/NIH

Additional AnatomicalAdditional Anatomical

FeaturesFeatures

Extra-ocularExtra-ocular

musclesmuscles

ConjunctivaConjunctiva

ScleraSclera

Neural visualNeural visual

pathwayspathways

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Blue=Left Brain

Purple=Right Brain

Deborah E. Hannula1, Daniel J. Simons1 and Neal J.

Cohen Imaging implicit perception: promise and pitfallsNature Reviews Neuroscience 6, 247-255 (March 2005) |

doi:10.1038/nrn1630

Cortical

Representation of

Visual Space

Visual PathwayVisual PathwayMost Common EyeMost Common Eye

Diseases Causing VIDiseases Causing VI

CataractCataract

GlaucomaGlaucoma

Macular DegenerationMacular Degeneration

Diabetic Eye DiseaseDiabetic Eye Disease

GlaucomaGlaucoma

StrokeStroke

Traumatic Brain InjuryTraumatic Brain Injury

CataractCataract General Eye ExaminationGeneral Eye Examination

HistoryHistory

Visual TestingVisual Testing

–– Visual acuity*Visual acuity*

–– MotilityMotility

–– Pupil testingPupil testing

–– Visual field*Visual field*

–– RefractionRefraction

–– Other (Other (StereopsisStereopsis, color, accommodative and, color, accommodative and

binocularity testing)binocularity testing)

Eye Health evaluationEye Health evaluation

Distance Visual AcuityDistance Visual Acuity

20/20 equals20/20 equals testing distance overtesting distance over

the the lettersizelettersize

20 is the smallest 20 is the smallest lettersizelettersize a normal a normal

eye can see at 20 feeteye can see at 20 feet

20/200 would mean the person could20/200 would mean the person could

only see the same letter if it was 10xonly see the same letter if it was 10x

larger or 10x closerlarger or 10x closer

SnellenSnellen Visual Acuity Visual Acuity

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Recorded as Cycles/Degree (CPD)Recorded as Cycles/Degree (CPD)

Contrast SensitivityContrast Sensitivity

10/16010/160

FeinbloomFeinbloom Visual Acuity Visual Acuity

Visual Acuity at NearVisual Acuity at Near

Same idea as distance acuitySame idea as distance acuity

Usually tested at 40 cm unlessUsually tested at 40 cm unlessdocumented otherwisedocumented otherwise

Normal is 20/20Normal is 20/20

May be different than distanceMay be different than distanceacuity!acuity!–– Why? Poor accommodation, poor contrastWhy? Poor accommodation, poor contrast

sensitivitysensitivity……

Lighthouse Near ChartLighthouse Near Chart

Visual fieldsVisual fields

Test of peripheral visionTest of peripheral vision–– Confrontation (Examiner testing)Confrontation (Examiner testing)

Full to examinerFull to examiner’’s fields field

Full to finger counting (FTFC)Full to finger counting (FTFC)

–– Humphrey visual fieldHumphrey visual fieldAutomated testAutomated test

Can be threshold or screening testCan be threshold or screening test

–– AmslerAmsler Grid GridCentral twenty degrees testedCentral twenty degrees tested

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Normal Visual FieldsNormal Visual Fields

90 degrees temporally and 70 degrees90 degrees temporally and 70 degrees

nasallynasally

Natural Natural blindspotblindspot at 15 degrees at 15 degrees

temporal to fixationtemporal to fixation

RefractionRefraction

RetinoscopyRetinoscopy

Subjective responses to changes inSubjective responses to changes in

lenseslenses

Will correct for error in lens andWill correct for error in lens andcorneal powerscorneal powers

Will NOT bring everyone to 20/20Will NOT bring everyone to 20/20

From NEI/NIH

Other testsOther tests

StereopsisStereopsis –– Testing depth perception Testing depth perception

Cover testCover test -- Testing how eye work -- Testing how eye work

togethertogether

Color testColor test –– Testing color vision Testing color vision

Accommodative testingAccommodative testing –– TestingTesting ability ability

to focus at nearto focus at near

General Eye ExaminationGeneral Eye Examination

Eye health evaluationEye health evaluation

–– Intraocular pressuresIntraocular pressures

–– Anterior segmentAnterior segment

–– Posterior segmentPosterior segment

Dilated Dilated fundusfundus exam best exam best

From NEI/NIH

Reading an Eye ReportReading an Eye Report

OD/OSOD/OS

OD=Right eyeOD=Right eye

OS=Left eyeOS=Left eye

OU=Both eyesOU=Both eyes

D=DistanceD=Distance N or NN or N’’=Near=Near

General Rule: Right eye results listedGeneral Rule: Right eye results listed

firstfirst

Reading an Eye ReportReading an Eye Report

Visual acuitiesVisual acuities–– Look for corrected and uncorrectedLook for corrected and uncorrected

cc (with correction) or sc (without correction)cc (with correction) or sc (without correction)

–– BEST CORRECTEDBEST CORRECTEDLOOK for acuities after refractionLOOK for acuities after refraction

May be better!May be better!

–– 10/40 means?10/40 means?Tested at 10 ftTested at 10 ft

Need to convert as you would any fractionNeed to convert as you would any fraction

E.g. 10/40 equivalent to 20/80E.g. 10/40 equivalent to 20/80

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Reading an Eye Report:Reading an Eye Report:

M-Notation (Metric)M-Notation (Metric)

1 M = 1.451 M = 1.45

mm =mm =

magazinemagazine

printprint

2 M = 1.952 M = 1.95

mm tall, =mm tall, =

newspapernewspaper

subheadlinsubheadlin

eses..

Reading an Reading an ““Eye ReportEye Report””

Glasses PrescriptionGlasses Prescription::

ODOD -1.00-1.00 -1.50 -1.50 X180X180

OSOS -2.50-2.50 -1.00 -1.00 X095X095

ADD +2.50ADD +2.50

Spherical correctionSpherical correction –– for for hyperopiahyperopia or myopia or myopia

Cylinder correction - for astigmatismCylinder correction - for astigmatism

AxisAxis –– orientation of cylinder orientation of cylinder

ADD ADD –– Bifocal power Bifocal power

Concave and Convex LensesConcave and Convex Lenses Cylinder for AstigmatismCylinder for Astigmatism

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Low Vision EvaluationLow Vision Evaluation

Different chartsDifferent charts

Devices evaluatedDevices evaluated

Focus on function and goalsFocus on function and goals–– Meet threshold acuities if possibleMeet threshold acuities if possible

Threshold acuitiesThreshold acuities–– Newsprint 20/50Newsprint 20/50

–– Large Print 20/100Large Print 20/100

Glare control evaluatedGlare control evaluated

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Low Vision evaluationLow Vision evaluation

goal for VRgoal for VR

Give access to standard text if at allGive access to standard text if at all

possiblepossible

Devices prescribed based onDevices prescribed based on

occupational goalsoccupational goals

–– EgEg. A custodian does not need. A custodian does not need

enlargement software for a computerenlargement software for a computer

Low Vision Devices forLow Vision Devices for

kidskids

Near DevicesNear Devices–– Bifocal or reading glassesBifocal or reading glasses

–– Stand and pocket magnifierStand and pocket magnifier

–– Bar Reader and Bar Reader and LupesLupes

–– CCTVCCTV

Distance DevicesDistance Devices

–– MonocularMonocular

–– BiopticBioptic

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IU School of OptometryIU School of Optometry

ClinicsClinics

IndianapolisIndianapolis

BloomingtonBloomington

CarmelCarmel