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Table 1.7.5 Classification of visual performance, distal and near; aids of vision enhancement and substitution

Vision

Visual acuity level

Person's visual performance

Reading distance

Aids

Normal

20/12-20/25

Full

>33 cm (binocular)

None/prescription glasses

Vision substitution means that tactile (e.g., Braille) or audible (e.g., computer-generated, audiotape) input replaces it.

Table 1.7.5 (continued) Classification of visual performance, distal and near; aids of vision enhancement and substitution

Vision

Visual acuity level

Person's visual performance

Reading distance

Aids

Near normal

20/30-20/60

Almost full

33-20 cm (binocular)

Stronger prescription glass, low-powder magnifier (<5 D)

Moderately low

20/70-20/160

Very good, but educational assistance often needed

16-10 cm (binocular)

Strong (half) prescription glass (with prisms for binocularity); strong magnifier (>8 D); videomagnifier

Severely low

20/200-20/400

Reasonable good with visual aids

8-5 cm (monocular)

High-power reading lens (12-20 D); high-power magnifier (>16 D); videomagnifier

Profoundly low

20/500-20/1000

Poor and laborious

4-2 cm (monocular)

Very highpower reading lens (24-48 D); very highpower magnifier (>28 D); videomagnifier; vision substitution

Table 1.7.5 (continued) Classification of visual performance, distal and near; aids of vision enhancement and substitution

Vision

Visual acuity level

Person's visual performance

Reading distance

Aids

Near blindness

20/1250-20/2500

Very poor, serves as an adjunct to nonvisual input/skills

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