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Categories of Visual Impairment

 

Categories of Visual Impairment

Category

Corrected

VA-Better Eye

WHO Definition

Working

Indian 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 Blindness

Total Blindness

 

  1. Blindness refers to a condition where a person suffers from any of the following
    1. Total absence of sight.
    2. Visual acuity not exceeding 6/60* or 20/200 (Snellen) in the better eye with best correcting lenses
    3. Limitation of field of vision subtending an angle of 20 degree or worse
    4. 6/60- means one can see at 6 metres what someone with standard vision could see from 60 metres away.
       
      In India a person with a VA < 6/60 is legally blind
       
      BLINDNESS: According to WHO, blindness is defined as visual acuity of <3/60 in the better eye
       
      Visual field of < 10o. It is also defined as inability to count fingers in daylight at a distance of 3 meters.
  2. Low Vision
     
    Person with low vision means a person with impairment of vision of less than 6/18 to 6/60 with best correction in the better eye or impairment of field in any one of the following categories:
    1. Reduction of fields less than 50 degrees
    2. Heminaopia with macular involvement
    3. Altitudinal defect involving lower fields
  3. Normal vision
     
    6/6 is considered normal vision.

Categories of Visual Correction

Category

Better Eye

Worse Eye

% Age Impairment

Category 0

6/9-6/18

6/24 to 6/36

20%

Category I

6/18-6/36

6/20 to Nil

40%

Category II

6/40-4/60 or field of vision 10o-20o

3/60 to Nil

75%

Category III

3/60 to 1/60 or field of vision 10o

F.C. at 1 ft. to Nil

100%

Category IV

F.C. at 1 ft. to Nil or field of vision 10o

F.C. at ft. to Nil

100%

One eyed person

F.C. at 1 ft. to Nil or field of vision 10o

6/6

30%

 


The WHO proposed a uniform criterion and defined blindness as “visual acuity of less than 3/60 (Snellen) or its equivalent”.

The WHO international classification of disease (1975 revision) described the levels of visual impairment. In order to facilitate the screening of visual acuity by non- specialized personnel, in the absence of appropriate vision charts, the WHO has now added the “inability to count fingers in daylight at a distance of 3 meters” to indicates less than 3/60 or its equivalent.

  1. Categories of visual impairment

 

Visual acuity

Categories of visual impairment

Maximum less than

Minimum equal to or better than

Low vision

1 6/18

6/60

 

2 6/60

3/60

 

3 3/60 (finger counting at 3 meter)

1/60 (finger counting at 1 meter)

Blindness

4 1/60 (Finger counting at 1 meter)

Light perception

 

5 No light perception

 

 

Table shows differentiation between “low vision” and blindness. If the patient reads 6/18 or better, he is coded “0”, i.e. no visual impairment.





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