Low vision aids
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Low Vision Aids. Who are all low vision patient. Having vision less than 6/18 in better eye Having vision 6/6 but field of vision is less than 20 Having vision 6/6, field of vision is normal, but contrast sensitivity is poor. Who need rehabilitation?.

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Low Vision Aids

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Low vision aids

Low Vision Aids


Who are all low vision patient

Who are all low vision patient

  • Having vision less than 6/18 in better eye

  • Having vision 6/6 but field of vision is less than 20

  • Having vision 6/6, field of vision is normal, but contrast sensitivity is poor


Who need rehabilitation

Who need rehabilitation?

  • Patient having some vision that patients need LV device

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


Causes

Causes

  • Macular degeneration

  • Diabetic Retinopathy

  • Glaucoma

  • Corneal disease

  • Neurological disorders Albinism

  • RP

  • Optic atrophy

  • Achromatopsia

  • Retinal problems


Low vision examination

Low vision Examination

  • Case History

  • RR

  • Field

  • Contrast sensitivity

  • Glare

  • Trial of low vision device

  • Instruction

  • Prescription

  • Follow-up


Treatment

Treatment

  • Optical aids

  • Non-optical aids

  • Electronic aids


Magnification

Magnification

  • Relative size magnification

    • Physically enlarging the size of an object of the retina

  • Relative distance magnification

    • Moving the object of regards towards the patient


Angular magnification

Angular magnification

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


Optical aids

Optical Aids

  • Telescope

  • Spectacle

  • Hand Magnifier

  • Stand Magnifier

  • Pocket Magnifier

  • Prismosphere


Distance vision

Distance vision

  • Telescopes

    • Galilean

    • Keplerian


Galilean

Galilean

  • + Objective, - eye piece

  • Low power ( 2 x to 4x )

  • Lighter, less expensive

  • Large exit pupil


Keplarian

Keplarian

  • + objective, + eye piece

  • Prism to invert image

  • Higher powers available

  • Poor light gathering


Types

Types

  • Hand held telescopes

  • Clip on telescopes

  • Spectacle mounted telescopes


Hand held

Hand held

  • Portable

  • Spotting intermediate & distance

  • Monocular

  • Inexpensive


Clip on

Clip on

  • 2.5 x to 4 x

  • Distance and near

  • Some hand held can be placed in flip-up clip


Spectacle mounted

Spectacle mounted

  • 1.7x to 8x

  • Special order

  • Bioptic

  • Full diameter

  • Wide angle

  • Expanded field when compared to others

  • It is also available head down type


Advantages of telescopes

Advantages of telescopes

  • Distance, intermediate or near

  • Variable working distance

  • Monocular & binocular

  • Spectacle mounted and hand held

  • Ideal range -2x to 4x


Disadvantage in telescope

Disadvantage in Telescope

  • Disadvantages

    • Restricted field

    • Reduced light gathering

    • Limited depth of focus

    • Requires co-ordination

    • Appearance and cost factor


Problems with optical system

Problems with optical system

  • Small field of view

  • When magnification increases contrast will be decrease

  • Close working distance

  • Lighting and glare

  • More aberrations


Optical aids available here

Optical aids available here

  • Telescope 3x; 4x

  • 2x hand held magnifier

  • 2x bar magnifier

  • 3x hand held illuminated magnifier

  • Pocket magnifier ( 3x, 6x)

  • 5.0 ds hand held illuminated magnifier

  • 4x wide field stand magnifier

  • 6x cutaway stand magnifier


Kesten baum s rule

Kesten baum’s rule

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

  • 6/60 = +10.0 ds


Spectacle

Spectacle

  • Advantages

    • Hands free

    • Wide field

    • Prolonged reading

    • Monocular or binocular


Disadvantages

Disadvantages

  • Fixing reading distance

  • Close reading distance

  • Positioning and posture

  • Head pain


Hand magnifiers

Hand Magnifiers

  • Advantages

    • Variable eye lens distance

    • Normal reading distance

    • Allows for eccentric viewing

    • May have own light source

    • Ideal range 10 to 20 dpts


Hand magnifier

Hand Magnifier

  • Disadvantages

    • Reduced field of view

    • Both hands occupied

    • Critical focus distance

    • Motion magnified ( tremor, arthritis )

    • Illumination reflected


Stand magnifiers

Stand Magnifiers

  • Advantages

    • May have own light source

    • Lens distance stabilized on page

    • Ideal for stroke, tremor, arthritis patients

    • Ideal stand range 12 – 24 dpts

    • Illuminated stand range 16 to 28 dpts


Stand magnifiers1

Stand Magnifiers

  • Disadvantages

    • Reduced field of view

    • Requires co-ordination

    • Need to use appropriate glasses

    • Illumination blocked and reflected by lens

    • Not be a portable


Prism sphere glasses

Prism sphere glasses

Advantages

  • +5.0 ds & 6.0 ds, 8.0ds prismospheres

  • 4x dome magnifier

  • Aspheric, +16.0 ds, +22.0 ds, +24.0 ds

  • 2.5 stand magnifier


Disadvantages1

Disadvantages

  • Very close Reading

  • Standard reading distance


Non optical aids

Non Optical Aids

  • Tints

  • Illumination

  • fluorescent lamp

    • Incandescent

    • Neodymium bulb

    • Halogen light

  • Contrast

    • Black pen

    • Typo scope ( black & white contrast)

  • Money finder


Electronic aids

Electronic aids

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


How to prescribe reading glairs

How to prescribe reading glairs

  • Best refraction

  • Give correct add power for near

  • Make sure patient is reading at correct distance

  • See it lighting helps

  • Try their own reading material (eg) newspaper

  • Are prisms needed

  • If the patient is monocular

    • No prism needed

    • Occlude fellow eye if it interferes – V/A is poor


Low vision aids

Thank you


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