Low Vision AidsLow Vision Aids

Who are all low vision patientWho are all low vision patient

Having vision less than 6/18 in better eyeHaving vision less than 6/18 in better eye Having vision 6/6 but field of vision is less Having vision 6/6 but field of vision is less

than 20than 20 Having vision 6/6, field of vision is normal, Having vision 6/6, field of vision is normal,

but contrast sensitivity is poorbut contrast sensitivity is poor

Who need rehabilitation?Who need rehabilitation?

Patient having some vision that patients Patient having some vision that patients need LV deviceneed LV device

Patient having less than 3/60, that patient Patient having less than 3/60, that patient wants mobility trainingwants mobility training

CausesCauses

Macular degenerationMacular degeneration Diabetic RetinopathyDiabetic Retinopathy GlaucomaGlaucoma Corneal diseaseCorneal disease Neurological disorders AlbinismNeurological disorders Albinism RPRP Optic atrophyOptic atrophy AchromatopsiaAchromatopsia Retinal problemsRetinal problems

Low vision ExaminationLow vision Examination

Case HistoryCase History RRRR FieldField Contrast sensitivityContrast sensitivity GlareGlare Trial of low vision deviceTrial of low vision device InstructionInstruction PrescriptionPrescription Follow-upFollow-up

TreatmentTreatment

Optical aidsOptical aids Non-optical aidsNon-optical aids Electronic aidsElectronic aids

MagnificationMagnification

Relative size magnificationRelative size magnification– Physically enlarging the size of an object of the Physically enlarging the size of an object of the

retinaretina

Relative distance magnificationRelative distance magnification– Moving the object of regards towards the patientMoving the object of regards towards the patient

Angular magnificationAngular magnification

Ratio of the angle of substance of the image Ratio of the angle of substance of the image formed by an optical instrument compared formed by an optical instrument compared to the actual object . E.g.. Telescopeto the actual object . E.g.. Telescope

Optical AidsOptical Aids

TelescopeTelescope SpectacleSpectacle Hand MagnifierHand Magnifier Stand Magnifier Stand Magnifier Pocket MagnifierPocket Magnifier PrismospherePrismosphere

Distance visionDistance vision

TelescopesTelescopes– GalileanGalilean– KeplerianKeplerian

GalileanGalilean

+ Objective, - eye piece+ Objective, - eye piece Low power ( 2 x to 4x )Low power ( 2 x to 4x ) Lighter, less expensiveLighter, less expensive Large exit pupilLarge exit pupil

KeplarianKeplarian

+ objective, + eye piece+ objective, + eye piece Prism to invert imagePrism to invert image Higher powers availableHigher powers available Poor light gatheringPoor light gathering

TypesTypes

Hand held telescopesHand held telescopes Clip on telescopesClip on telescopes Spectacle mounted telescopesSpectacle mounted telescopes

Hand heldHand held

PortablePortable Spotting intermediate & distanceSpotting intermediate & distance MonocularMonocular InexpensiveInexpensive

Clip onClip on

2.5 x to 4 x2.5 x to 4 x Distance and nearDistance and near Some hand held can be placed in flip-up clipSome hand held can be placed in flip-up clip

Spectacle mountedSpectacle mounted

1.7x to 8x1.7x to 8x Special orderSpecial order BiopticBioptic Full diameterFull diameter Wide angleWide angle Expanded field when compared to othersExpanded field when compared to others It is also available head down typeIt is also available head down type

Advantages of telescopesAdvantages of telescopes

Distance, intermediate or nearDistance, intermediate or near Variable working distanceVariable working distance Monocular & binocularMonocular & binocular Spectacle mounted and hand heldSpectacle mounted and hand held Ideal range -2x to 4xIdeal range -2x to 4x

Disadvantage in TelescopeDisadvantage in Telescope

DisadvantagesDisadvantages– Restricted fieldRestricted field– Reduced light gatheringReduced light gathering– Limited depth of focusLimited depth of focus– Requires co-ordinationRequires co-ordination– Appearance and cost factorAppearance and cost factor

Problems with optical systemProblems with optical system

Small field of viewSmall field of view When magnification increases contrast will When magnification increases contrast will

be decreasebe decrease Close working distanceClose working distance Lighting and glareLighting and glare More aberrationsMore aberrations

Optical aids available hereOptical aids available here

Telescope 3x; 4xTelescope 3x; 4x 2x hand held magnifier2x hand held magnifier 2x bar magnifier2x bar magnifier 3x hand held illuminated magnifier3x hand held illuminated magnifier Pocket magnifier ( 3x, 6x)Pocket magnifier ( 3x, 6x) 5.0 ds hand held illuminated magnifier5.0 ds hand held illuminated magnifier 4x wide field stand magnifier4x wide field stand magnifier 6x cutaway stand magnifier6x cutaway stand magnifier

Kesten baum’s ruleKesten baum’s rule

The inverse of the visual acuity = the add The inverse of the visual acuity = the add required to read 1m pointrequired to read 1m point

6/60 = +10.0 ds6/60 = +10.0 ds

SpectacleSpectacle

AdvantagesAdvantages– Hands freeHands free– Wide fieldWide field– Prolonged readingProlonged reading– Monocular or binocularMonocular or binocular

DisadvantagesDisadvantages

Fixing reading distanceFixing reading distance Close reading distanceClose reading distance Positioning and posturePositioning and posture Head painHead pain

Hand MagnifiersHand Magnifiers

AdvantagesAdvantages– Variable eye lens distanceVariable eye lens distance– Normal reading distanceNormal reading distance– Allows for eccentric viewingAllows for eccentric viewing– May have own light sourceMay have own light source– Ideal range 10 to 20 dptsIdeal range 10 to 20 dpts

Hand MagnifierHand Magnifier

DisadvantagesDisadvantages– Reduced field of viewReduced field of view– Both hands occupiedBoth hands occupied– Critical focus distanceCritical focus distance– Motion magnified ( tremor, arthritis )Motion magnified ( tremor, arthritis )– Illumination reflectedIllumination reflected

Stand MagnifiersStand Magnifiers

AdvantagesAdvantages– May have own light sourceMay have own light source– Lens distance stabilized on pageLens distance stabilized on page– Ideal for stroke, tremor, arthritis patientsIdeal for stroke, tremor, arthritis patients– Ideal stand range 12 – 24 dptsIdeal stand range 12 – 24 dpts– Illuminated stand range 16 to 28 dptsIlluminated stand range 16 to 28 dpts

Stand MagnifiersStand Magnifiers

DisadvantagesDisadvantages– Reduced field of viewReduced field of view– Requires co-ordinationRequires co-ordination– Need to use appropriate glassesNeed to use appropriate glasses– Illumination blocked and reflected by lensIllumination blocked and reflected by lens– Not be a portableNot be a portable

Prism sphere glassesPrism sphere glasses

AdvantagesAdvantages +5.0 ds & 6.0 ds, 8.0ds prismospheres+5.0 ds & 6.0 ds, 8.0ds prismospheres 4x dome magnifier4x dome magnifier Aspheric, +16.0 ds, +22.0 ds, +24.0 dsAspheric, +16.0 ds, +22.0 ds, +24.0 ds 2.5 stand magnifier2.5 stand magnifier

DisadvantagesDisadvantages

Very close ReadingVery close Reading Standard reading distanceStandard reading distance

Non Optical AidsNon Optical Aids

TintsTints IlluminationIllumination fluorescent lampfluorescent lamp

– IncandescentIncandescent– Neodymium bulbNeodymium bulb– Halogen lightHalogen light

ContrastContrast– Black penBlack pen– Typo scope ( black & white contrastTypo scope ( black & white contrast ))

Money finderMoney finder

Electronic aidsElectronic aids

CTV – closed circuit televisions allow printed CTV – closed circuit televisions allow printed hand written and graphic material to be hand written and graphic material to be electronically displayed, magnified and electronically displayed, magnified and enhanced on a television monitor. Contrast enhanced on a television monitor. Contrast can be increased and the image polarity can be increased and the image polarity reversed allowing white letters to be reversed allowing white letters to be displayed on a black back ground or the displayed on a black back ground or the reverse. Patients also have a choice of color reverse. Patients also have a choice of color displatts. displatts.

How to prescribe reading glairsHow to prescribe reading glairs

Best refractionBest refraction Give correct add power for nearGive correct add power for near Make sure patient is reading at correct distanceMake sure patient is reading at correct distance See it lighting helpsSee it lighting helps Try their own reading material (eg) newspaperTry their own reading material (eg) newspaper Are prisms neededAre prisms needed If the patient is monocular If the patient is monocular

– No prism neededNo prism needed– Occlude fellow eye if it interferes – V/A is poorOcclude fellow eye if it interferes – V/A is poor