Glaucoma is characterized by classical
visual field loss patterns. In early glaucoma there is mainly restriction of
the peripheral fields. But in later stages central vision is also impaired,
affecting the quality of life of the glaucoma patient. However, there are some
studies which have shown that even central vison can be affected early in the
course of glaucoma. As visual deterioration develops, there occurs a situation
in which usual visual rehabilitation methods such as glasses become
ineffective. In such cases low vision aids (LVA) may prove helpful.
Overall, visual rehabilitative services
include mobility training, adaptive skills training, low vision instruction
career services and training, psychological counseling and others.
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Low vision aids are devices which help
people use their sight to better advantage. These aids fall into two
categories, namely, optical and non-optical. The former includes optical
lenses, such as magnifiers or telescopes. The non-optical devices include
visors, filters, reading slits, stands, lamps and large print. The basic
principle of all low vision optical devices is to magnify.
OPTICAL DEVICES:
1. Magnifying spectacles
(high plus reading glasses) used for reading any material, writing and looking
at objects from close range. The spectacle produces magnification of 1/4th of
the power of the lens. For binocular corrections prism spectacles half eyed of
full field with base in (to compensate for convergence angle of the eye) are
used.
2. Magnifiers: Handheld low
vision magnifiers are helpful for looking in a mirror, telling the time on a
watch, and other quick viewing tasks. The ones with self-contained illumination
can be used when surrounding illumination is dim. The low vision magnifiers
that are mounted on a stand are useful for reading books and doing close-up
work such as needlepoint and quilting.
3. Telescopes: These are
prescribed for distance, near and intermediate tasks like reading signs,
recognizing people, reading from blackboard at more than 2-meters distance,
watching television, games or traffic signals. These can be hand held
monocular, clip on, spectacle mounted, monocular or binocular, bioptic designs.
4. E-Scoop glasses: E-Scoop
Glasses are custom designed optics that combine 5 unique optical
characteristics to maximize the remaining vision of a low vision patient. These
5 optical features focus the image onto the part of the eye that is least
affected by vision loss, thereby maximizing the patient’s current vision.
5. Envision glasses: Envision
Glasses are AI-powered smart-glasses with an integrated camera and built-in
speakers that speak out the visual world. It is a wearable device that
significantly improves the daily life of people that are blind or have low
vision. It provides an intuitive and easy way to access all kinds of visual
information around them.
6. IrisVision: These electronic
glasses use a highly innovative assistive technology solution, which is
registered with the FDA as a Class-1 medical device.
7. Acesight: It is a
wearable LVA is based on ‘Augmented Reality’ technology. It offers an
HD display floating before the eyes, through a pair of head-mounted goggles,
which are connected to a controller through a wire. It provides up to 15X
magnification, while the wired controller allows one to customize the colors
and contrast. This electronic eyewear is designed to cater to the needs of
people with visual acuity ranging from 20/100 to 20/800.
8. NuEyes Pro: It is a
head-worn lightweight and wireless pair of smart glasses, which can be
controlled either through a wireless handheld controller or a set of voice
commands. A camera on the front of the glasses captures the image and displays
it magnified inside of the lenses. These glasses provide up to 12X magnified images.
9. MyEye2: These are low
vision electronic glasses designed to make reading, writing, recognizing
faces and various other daily activities easier for visually impaired people. A
light attachable camera distinguishes it from an ordinary pair of glasses, which
is mounted on the frame of the glasses by the side.
NON-OPTICAL DEVICES:
1. Typoscopes are used to
enhance images and reduce glare. Felt tipped pens, bold lined papers, writing
guide, large print materials and adequate lighting on print are helpful methods
in assisting vision by enhancing contrast. Reading stands are useful by providing
a hands-free comfortable working distance.
2. Assistive Technologies:
Desktop electronic magnifiers are low vision aids that display reading material
placed on a tray. The person with low vision moves the reading material as
needed and views it on a screen at a suitable height. Most of these magnifiers
have an independent monitor, but others allow for connection to a TV or
computer monitor. Often these devices are a bit heavy and therefore are not
portable. There are portable low vision electronic magnifiers, which are of two
main types. The handheld ones can be carried in a pocket or handbag, and are
used to read labels in a grocery store or pharmacy, menus in a restaurant,
credit card slips, price tags and more. The other type has a camera fixed to a
stand. Therefore, a still image of the reading material can be taken and can be
read later on a portable device.
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Supernova magnifier |
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Juno Magnifier |
LIMITATION: The non-availability of trained personnel
as well as the financial cost and practicality of the LVAs remains a limitation
for their usage in glaucoma clinics.