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Low Vision Aids

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?.

irene-ramsey
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Low Vision Aids

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  1. Low Vision Aids

  2. 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

  3. Who need rehabilitation? • Patient having some vision that patients need LV device • Patient having less than 3/60, that patient wants mobility training

  4. Causes • Macular degeneration • Diabetic Retinopathy • Glaucoma • Corneal disease • Neurological disorders Albinism • RP • Optic atrophy • Achromatopsia • Retinal problems

  5. Low vision Examination • Case History • RR • Field • Contrast sensitivity • Glare • Trial of low vision device • Instruction • Prescription • Follow-up

  6. Treatment • Optical aids • Non-optical aids • Electronic aids

  7. 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

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

  9. Optical Aids • Telescope • Spectacle • Hand Magnifier • Stand Magnifier • Pocket Magnifier • Prismosphere

  10. Distance vision • Telescopes • Galilean • Keplerian

  11. Galilean • + Objective, - eye piece • Low power ( 2 x to 4x ) • Lighter, less expensive • Large exit pupil

  12. Keplarian • + objective, + eye piece • Prism to invert image • Higher powers available • Poor light gathering

  13. Types • Hand held telescopes • Clip on telescopes • Spectacle mounted telescopes

  14. Hand held • Portable • Spotting intermediate & distance • Monocular • Inexpensive

  15. Clip on • 2.5 x to 4 x • Distance and near • Some hand held can be placed in flip-up clip

  16. 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

  17. Advantages of telescopes • Distance, intermediate or near • Variable working distance • Monocular & binocular • Spectacle mounted and hand held • Ideal range -2x to 4x

  18. Disadvantage in Telescope • Disadvantages • Restricted field • Reduced light gathering • Limited depth of focus • Requires co-ordination • Appearance and cost factor

  19. Problems with optical system • Small field of view • When magnification increases contrast will be decrease • Close working distance • Lighting and glare • More aberrations

  20. 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

  21. Kesten baum’s rule • The inverse of the visual acuity = the add required to read 1m point • 6/60 = +10.0 ds

  22. Spectacle • Advantages • Hands free • Wide field • Prolonged reading • Monocular or binocular

  23. Disadvantages • Fixing reading distance • Close reading distance • Positioning and posture • Head pain

  24. 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

  25. Hand Magnifier • Disadvantages • Reduced field of view • Both hands occupied • Critical focus distance • Motion magnified ( tremor, arthritis ) • Illumination reflected

  26. 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

  27. 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

  28. 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

  29. Disadvantages • Very close Reading • Standard reading distance

  30. Non Optical Aids • Tints • Illumination • fluorescent lamp • Incandescent • Neodymium bulb • Halogen light • Contrast • Black pen • Typo scope ( black & white contrast) • Money finder

  31. 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.

  32. 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

  33. Thank you

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