The document discusses low vision devices for enhancing near vision functionality, defining low vision using WHO criteria. It describes various aids, including optical devices like magnifiers and telescopic glasses, as well as electrical devices like CCTV systems, highlighting their advantages and disadvantages for patients with low vision. Key factors such as accommodation, reading distance, and patient-specific adaptations are also mentioned for effective usage of these aids.

1. Low Vision Devices For
Near
Presenter
Aarju Singh
3rd year B.sc optometry

2. Def of Low Vision
According to WHO :- a person with low vision is one
who
 Has a impairment of visual functioning even after treatment
and /or standard refractive correction
 Has a visual acuity less than 6/18 to light perception
 Or visual field less than 10 degree from the point of fixation
 But who uses , or is potentially able to use, vision for
planning and/or execution of a task.

3. LOW VISION AIDS
The assistance given to the LV
patient to maximize the
functional level of vision by
optical or non- optical means is
called LV aids .
The optical device can be used
for distance and near .

4. Near Optical Devices :- are used for
close-up, detail viewing, such as reading,
writing, and sewing.
It includes :-
 Spectacles Magnifier
 Magnifiers :- Hand and Stand magnifier
 Magnifying reading Glasses
 Clip - on loupes
 Telemicroscopic Glasses
 Electrical devices :- CCTV, HMD

5. Spectacle magnifiers
 High plus reading glasses to magnify the images
 Given as an add to the best distance refraction
 Used for Near work

6. Contd…
 Amount of add needed depends on the accommodation and
reading distance
 Reading add can be predicted using the kestenbaum rule i.e
the amount of add needed to read 1M print is the inverse of
VA fraction
 However usually greater add is required than predicted as
the patient also has reduced contrast sensitivity

7. Contd…
 If the patient is monocular ,the poorer eye may be occulded
if it improves the functioning
 When binocular correction are needed :-
base in prism are added to compensate for
convergence angle.
Optical center may be decentered.
 Aspheric lenses may be used to reduce lenticular distortion

8. 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 accepatble

9. Disadvantages
 Higher the power ,closer the reading
distance
 Closer reading distances causes fatigue
and unacceptable posture
 Patient with eccentric fixation are unable
to fix through these glasses

10. Magnifiers
 Useful for near work
 By keeping at near and distance ,we can
achieve different magnification
Two types :- Hand magnifier
Stand magnifier

11. Hand magnifiers
 It consist of a convex lens surrounded by
a plastic or metal carrier attached to a
handle .
 For maximum magnification with hand
magnifier place the object at the focal
point.
 The distance from a hand magnifier to
the printed page must be kept constant .

12. Contd…
 To find this distance start the lens on
the page and slowly pull it away from
the print until optimal focus is reached.
 It should be used with distance glasses
 If the material is brought closer to your
eyes , bring the reading material closer
as well.
 Available from +4.0 to 68.0 D (1x-17x)

13.  Available designs
- Aspheric – reduces thickness and peripheral distortion
- Aplantic – flat and wide distortion free field and good clarity.
- Bispheric – eliminating aberrations from both surfaces.
 Most patients accept upto 6x magnification
Contd…

14. Advantages
 The eye to lens distance can be varied.
 Patient can maintain normal reading distance
 Work well with patient with eccentric viewing
 Some have light source which further enhances
vision
 Easily available ,over the counter

15. Disadvantage
 One hand tied up
 Difficult to held steady in proper position
at all times
 Limited FOV ,depends on eye to lens
distance
 Patient with tremors ,arthritis etc have
difficulty holding the magnifier

16. Stand Magnifier
 Magnifiers are stand mounted
 Patient needs to place the
stand magnifier on the reading
material and move across the
page to read
 Has a fixed focus

17. Types
 Variable focusable stand magnifier :- Have
lenses that can be adjusted closer to or
farther away from the material .
 Fixed focus stand magnifier :- lens at fixed
distance from the base.

18. Advantages
 Do not have to hold
 Can slide across page
 Constant lens to page distance
 Inexpensive and easily available
Disadvantages
 FOV is reduced or limited
 To close reading posture is uncomfortable for the pt
 Block good lighting unless self illuminated
 Heavy , fatigue problem

19. Magnifiers Reading glasses
 Allow an individual to read for longer periods of time
 Also called as “microscope”
Advantages
 Wide field of view
 Portable
 Hands are free
Disadvantages
 Holding things very close

20. Clip-on loupes
 Clip-on loupe attaches to glasses and allow
the person to be hands free while viewing
text , computer screen etc.
Advantage
 Hands are free
 Convenient and easy to use flip
 Inexpensive
Disadvantage
 For larger loupe , they may heavy
 distracting

22. Telemicroscopic Glasses
 Eyeglass mounted telescopes
can be made to focus at any
WD.
Advantages
 More comfortable working
distances
 Hands are free
 Have excellent optics

23. Disadvantages
 Smaller FOV
 Reading difficulty especially if a book is
heavy ,reading longer period of time
 Image may be some what dark
 Feel heavy on your nose
 Expensive

24. Electrical devices
CCTV
 An electronic magnification
system for reading and writing
 Consist of 3 major components
camera
monitor
movable reading platform

25. Contd..
 It provide excellent contrast and magnification ,color .
 Magnification upto 60x .
Advantages
 Provides distortion free ,brighter ,magnified image
with enhanced contrast on a larger screen .
Disadvantages
 Expensive , heavy and difficult move around .
 Difficulty in operation for patient .

26. Head –mounted Display
 It is display device ,worn
on the head or as a part of
a helmet ,that has a small
display optic in front of
one (monocular HMD) or
each eye(binocular HMD).