Identifying Visual Impairments

Children With Developmental Challenges 3(2+1)

Lesson 11 : Sensory Impairment – Visual

Identifying Visual Impairments

Among pre-school and school children the following should be observed and noted as possible indications of visual difficulty

  1. Strabismus; nystagmus.
  2. How the child uses his eyes: tilting his head, holding objects close to his eyes, rubbing his eyes, squinting, displaying sensitivity to bright light and rolling his eyes.
  3. In-attention to visual objects and visual tasks such as looking at pictures and reading.
  4. Awkwardness in games requiring eye-hand co-ordination.
  5. Avoidance of tasks that require close eye work
  6. Affinity to tasks that require distance vision.
  7. Any complaints about inability to see.

Tests used for visual efficiency

  1. Observation
  2. The Snellen test chart
  3. The Massachusetts vision test
  4. Keystone telebinocular
  5. Ortho ratel
  6. Retenoscopy

The Snellen test for visual screening: is the most widely used because of the ease and speed with which it can be administered to a child by a nurse or a teacher and because it can be used with young children.


The snellen test chart consists of rows of letters (or E’s in various positions for use with young children and illiterates), each row in a different size print. Each size letter represents an optical measure. The “20 feet” row is so designed because it has been found that the person with normal vision can read that line at a distance of 20 feet.

The notation used to indicate performance on the Snellen chart should be interpreted as follows. This subject sees at a distance of numerator feet the line that a person with normal vision sees at a distance of denominator feet. Thus 20/70 means that the subject sees at 20 feet what with normal vision could see at 70 feet.

Snellen notation and the corresponding percentage of visual efficiency are as follows.


Retenoscopy: The test is performed in a darkened room. Each eye is tested individually.


Last modified: Tuesday, 10 April 2012, 10:51 AM