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?
 Patient having some vision that patients
need LV device
 Patient having less than 3/60, that patient
wants mobility training
Causes
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Macular degeneration
Diabetic Retinopathy
Glaucoma
Corneal disease
Neurological disorders Albinism
RP
Optic atrophy
Achromatopsia
Retinal problems
Low vision Examination
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Case History
RR
Field
Contrast sensitivity
Glare
Trial of low vision device
Instruction
Prescription
Follow-up
Treatment
 Optical aids
 Non-optical aids
 Electronic aids
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
 Ratio of the angle of substance of the image
formed by an optical instrument compared
to the actual object . E.g.. Telescope
Optical Aids
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Telescope
Spectacle
Hand Magnifier
Stand Magnifier
Pocket Magnifier
Prismosphere
Distance vision
 Telescopes
– Galilean
– Keplerian
Galilean
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+ Objective, - eye piece
Low power ( 2 x to 4x )
Lighter, less expensive
Large exit pupil
Keplarian
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+ objective, + eye piece
Prism to invert image
Higher powers available
Poor light gathering
Types
 Hand held telescopes
 Clip on telescopes
 Spectacle mounted telescopes
Hand held
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Portable
Spotting intermediate & distance
Monocular
Inexpensive
Clip on
 2.5 x to 4 x
 Distance and near
 Some hand held can be placed in flip-up clip
Spectacle mounted
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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
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Distance, intermediate or near
Variable working distance
Monocular & binocular
Spectacle mounted and hand held
Ideal range -2x to 4x
Disadvantage in Telescope
 Disadvantages
– Restricted field
– Reduced light gathering
– Limited depth of focus
– Requires co-ordination
– Appearance and cost factor
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
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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
 The inverse of the visual acuity = the add
required to read 1m point
 6/60 = +10.0 ds
Spectacle
 Advantages
– Hands free
– Wide field
– Prolonged reading
– Monocular or binocular
Disadvantages
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Fixing reading distance
Close reading distance
Positioning and posture
Head pain
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
 Disadvantages
– Reduced field of view
– Both hands occupied
– Critical focus distance
– Motion magnified ( tremor, arthritis )
– Illumination reflected
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 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
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
Disadvantages
 Very close Reading
 Standard reading distance
Non Optical Aids
 Tints
 Illumination
 fluorescent lamp
– Incandescent
– Neodymium bulb
– Halogen light
 Contrast
– Black pen
– Typo scope ( black & white contrast )
 Money finder
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
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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