Page 55 - DEDU506_SPECIAL_EDUCATION_ENGLISH

Unit 7: Visually Impaired: Definition, Types and Characteristics

• Limitation of the field of vision subtending an angle of 20 degree or worse. Notes
For deciding the blindness, the visual acuity as well as field of vision have been considered.
The WHO working definition of Low Vision (WHO, 1992) is as follows:
“A person with low vision is one who has impairment of visual functioning even after treatment,
and/or standard refractive correction, and has a visual acuity of less than 6/18 to light perception or
a visual field of less than 10 degrees from the point of fixation, but who uses, or is potentially able
to use, vision for the planning and/or execution of a task”.
The points emphasized that there is significantly reduced vision, visual performance is affected but
that there still is vision that can be used. This last point is very important: if there is usable vision,
training to use that vision might be possible. In addition, this person is not labelled blind.
Table 7.1
Categories of visual impairment
Category Corrected WHO Definition Indian
VA-better eye Standard Working Definition
0 6/6-6/18 Normal Normal Normal
1 <6/18-6/60 Visual Impairment Low Vision Low Vision
2 <6/60-3/60 Severe Visual Impairment Low Vision Blind
3 <3/60-1/60 Blind Low Vision Blind
4 <1/60-PL Blind Low Vision Blind
5 NPL Blind Total Total
Blindness Blindness
7.1.2 Persons with Deafblindness

Deafblindness is a condition presenting other difficulties than those caused by deafness and blindness.
It is an “umbrella” term which can include children and adults who may suffer from varying degrees
of visual and hearing impairment, perhaps combined with learning difficulties and physical
disabilities, which can cause:
• severe communication
• developmental, and
• educational problems.
It includes children and adults who are:
• blind and profoundly deaf
• blind and severely or partially hearing
• partially sighted and profoundly deaf
• partially sighted and severely or partially hearing
7.1.3 Visual Acuity
It refers to the ability of the eye to see details. The visual acuity for distance is measured as the
maximum distance at which person can see a certain object, divided by the maximum distance at
which a person with normal eyesight can see the same object. Thus a visual acuity of 6/60 means that
the person examined cannot see, at a distance of 6 meters, the object which a person with normal
eyesight would be able to see at 60 meters. If vision is so impaired that to see the biggest E of the E-
chart, the person has to come within 6 meters or even nearer, he is considered blind. The simplest
method of testing visual acuity is to see whether the person can count fingers at a distance of six
meters.

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