This document discusses different types of low vision devices used to help people with low vision. It describes optical devices like telescopes, magnifying spectacles, and magnifiers that use lenses to improve vision. It also discusses non-optical devices like illumination aids, reading stands, and software that help without using lenses. A variety of telescopes, magnifiers, and other low vision devices are presented along with their uses, advantages, and disadvantages. The document provides an overview of the options available to enhance vision for those with low vision.

1. Low Vision Devices
Different types of telescopes
Magnifiers and other devices in low vision
Presented By:- Guided By:-
Mohammad Aamir Miss Sravani Reddy Mam
B.Optometry 5th sem Faculty- SLAS ITM
School of Life & Allied Science University Raipur
ITM University Raipur,
Chhattisgarh

2. Low vision:- A condition caused by eye disease, in which visual acuity is 20/70
or poorer in the better-seeing eye and cannot be corrected or improved with regular
eyeglasses.

3. Low vision device:- A device to help to improve visual ability of a person
with low vision. Low vision devices may be optical or non-optical. Optical devices
such as a magnifying glass involve the use of lenses to improve vision whereas non-
optical devices such as large print help bring images closer to the eyes.

4. Types of low vision devices
 Optical:-
1- Distance
2- Near
 Magnifiers
 Electronic devices
 Non Optical

5. Low vision optical devices for distance
Telescopes:-
 Work on the principle of angular magnification
 Telescopes with magnification from 2x to 10x are prescribed
 They can be prescribed for distance, intermediate and near tasks
 Field of view decreases with magnification
Types:-
 Hand held monocular
 Clip on design
 Bioptic design: mounted on a pair of eye glasses

6. Hand held monocular telescopes Clip on design
Bioptic design

7. Principal:-
 Telescopes consist of two lenses ( in practice two optical system) mounted such
the focal point of the objective coincides with the focal point of the ocular.
 Objective lens is converging lens
Galilean telescope
 The eye piece is a negative lens and the
objective is a positive lens
 Resultant image is a virtual and erect
 Loss of light reduces brightness of the image
 Field quality is poor
Keplerian telescope
 Both eye piece and objective are positive leens
 Resultant image is real and inverted. Prisms are
incorporated to erect the image
 Loss of light is more in this system
 Field quality is relatively good

8.  Magnification of a telescope is given by the formula M=fₒ/fₑ
 Telescopes can be used to focus near objects by
- changing the distance between objective and ocular lens
- increasing the power of the objective lens

9. Advantages:-
Only possible device to enhance distant vision
Disadvantages:-
 Restriction of the field of view
Appearance and apprehension
Expensive and costly
Depth perception is distorted

10. Low vision optical devices for near
Magnifying Spectacles
 High plus reading glasses to magnify the images
Given as an add to the best distance refraction
Reading distance is calculated by 100 divided by add
Magnification is 1/4th the power of lens
Used for near work
Amount of add needed depends on the accommodation and the reading distance

11. Advantages:-
 Hands are free
Field of view larger when compared to telescope
 Greater reading speed
 Can be given in both monocular and binocular forms
 More portable
 Cosmetically acceptable
Disadvantages:-
 Higher the power, closer the reading distance
 Close reading distance causes fatigue and unacceptable posture
 Patients with eccentric fixation are unable to fix through these glasses

12. Low vision optical devices for near
Magnifiers
 Useful for near work
 Designed to be held close to the reading material to enlarge the image
 The eye lens distance should be minimum to achieve larger magnification
Two types;
 Hand magnifier
 Stand magnifiers
Hand Magnifiers Stand Magnifiers

13. Hand Magnifiers
 Available from +4.0 to +68.0 D
 Available in three designs:-
• Aspheric – reduces thickness and peripheral distortion
• Aplantic - flat and wide distortion free field and good clarity
• Biaspheric – eliminating aberrations from both surfaces
 Most patients accept up to 6x magnification

14. Advantages:-
 The eye to lens distance can be varied
 Patient can maintain normal reading distance
 Work well with patients with eccentric viewing
 Some have light source which further enhance vision
 Easily available, over the counter
Disadvantages:-
 It occupies both hands
 Patients with tremors, arthritis etc have difficulty holding the magnifier
 Maintaining focus is a problem especially for elderly
 Field of vision is limited

15. Stand Magnifiers
 The magnifiers are stand mounted
 The patient needs to place the stand magnifier on the reading material and move
across the page to read
 Has a fixed focus
Advantages:-
 They are a choice for patients with tremors, arthritis and constricted visual
fields
Disadvantages:-
 Field of vision is reduced
 Too close reading posture is uncomfortable for the patient
 Blocks good lighting unless self illuminated

17. Low vision optical devices for near
Closed circuit television system
 Closed circuit television system (CCTV) consists of a monitor, a camera and a
platform to place the reading text
 It has control for brightness, contrast and change of polarity
 Magnification varies from 3X to 60X

18. Non Optical Devices
Illumination
Positioning:-
 Light source should be to the side of better eye
 Moving light closer will yield higher illumination
Higher levels of illumination is needed in patients with:-
 Lost cone function (macular degeneration)
 Glaucoma retinopathy
 Retinitis pigmentosa, Chorioretinitis
Reduced illumination:-
 Albinism
 Aniridia

19. Non Optical Devices
Reading stand:-
 Easy comfortable posture to the patient

20. Non Optical Devices
Writing Guide
 Black cards with rectangular cut outs horizontally along the card
 The patient can feel the empty cut out spaces and write

21. Non Optical Devices
Signature guide

22. Non Optical Devices
Typo scope / Reading guide
 Masking device with a line cut out from an opaque, non reflecting black plastic
or thick paper
 Reduces glare and controls contrast

23. Non Optical Devices
Notex
 It is a rectangular piece of cardboard with steps on top right corner which helps
in identifying the currency of the note
 1st cut indicates Rs. 100, 2nd cut indicates Rs. 50, and so on.

24. Non Optical Devices
Relative size devices
 Larger object subtends a larger visual angle at the eye and is thus easier to
resolve
 Large print material
 Large type playing cards, computer keyboards
 Enlarged clocks, telephones, calendars

25. Non Optical Devices
Computer software
 Jaws screen reading software
 Connect out loud internet and email software
 Magic 8.0 screen magnification software and speech

26. Non Optical Devices
Glare reducing devices
 Glare is described as unwanted light
 It is disabling in patients with cataracts, corneal opacities, albinism, retinitis
pigmentosa
 Devices to prevent glare:
 Sunglasses
 Caps
Umbrella
 Polaroid glasses
 NoIR filters
 Corning photochromic filters
(CPF glasses)

27. Non Optical Devices
CPF Glasses
 Attenuate 100% of UVB wavelengths.
 Block 99% of UVA wavelengths.
 Block 99% of UVA wavelengths. in the eye, causing discomfort and hazy
illusion.
 Attenuate 98% of high-energy blue light, with exception of CPF 450, which is
96% of high-energy blue light.
 The number of the CPF glasses correspond to wavelength in nanometers above
which light is transmitted

28. Non Optical Devices
Color and contrast enhancement
 Maximize contrast by using a light color against black or dark color
 Choose colors in the room or working area which have high contrast

29. Non Optical Devices
Pinhole Glasses
 Multiple holes of approximately 1mm size are made in the glasses
 The distance between the holes should be at least 3-3.5 mm or
approximately the size of the pupil
 Used in patients with corneal opacities or conditions with irregular
reflexes
 Not used in patients with central field defects as it reduces
illumination and visual acuity

30. Non Optical Devices
Mobility Assisting Devices
 Patients with low vision suffer a major problem of mobility
 Long canes
 Strong portable lights

32. Help when there is no cure

34. Reference
 Low Vision Aids – Monika Chaudhry
 https://www.slideshare.net/AsthaJain1/low-vision-aids?qid=1bf23c50-34dd-
43ee-a967-5af1a1eb1fc9&v=&b=&from_search=1
 Images from – google images
https://www.google.com/search?biw=1094&bih=494&tbm=isch&sxsrf=ACYBGN
RfZI8U7Rsfsop_ntFK8WZp_CrGJQ%3A1568775652255&sa=1&ei=5J2BXaWeD8vYz
7sPy4-b-
Ak&q=CPF+glasses+low+vision&oq=CPF+glasses+low+vision&gs_l=img.3...11012
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img.....10..35i362i39j35i39j0i67j0j0i8i30j0i30j0i24.ffWPBPcfEaw&ved=0ahUKEwil
oPDbsNnkAhVL7HMBHcvHBp8Q4dUDCAc&uact=5