Discussion:
Children are not mentioned as a special group in this classification. Visual impairment and disability affect an infant and a child different from adult persons. In developing countries visual impairment is mostly a paediatric problem and thus classification of paediatric visual impairment is important.

Definitions of "infant" and "child" need to be agreed upon.

Addition to the chapter:

Chapter 4 (0400-0499) Functions of the eye and of adjoining structures in infants and children.

Since visual functions mature until 9-10 years after which also examination of visual functions resembles that of an adult person, the upper age limit is 10 (ten) years. The boundary between infancy and childhood is the age when visual functions can be measured using optotype tests and other tests requiring similar communication, i.e. <4 (four) years.

Oculomotor functions and accommodation in infants and children

incl. diplopia, seeing double

Functions of the external musculature of the eye

: voluntary eye movements of the eyes; tracking movements of the eyes; saccadic movements of the eyes

Assessment of oculomotor functions is equal to that of adult persons but needs to mention whether the development of functions is at age appropriate level or not. Measurement of accommodation is particularly important in hypotonic infants.

Visual-sensory functions

Visual acuity at distance

Visual acuity is measured using line tests,

Normal vision, visual acuity better than one third of the mean visual acuity of normally sighted children at the same age (The age norms need to be agreed upon. In normally sighted children visual acuity is often 6/12 - 6/10 at the age of 4-5 years and 6/9 - 6/6 at the age of 6 years and later - during the first measurement. Repeated measurements result in visual acuity values that are several lines better, which actually is the true visual acuity of the child. Binocular values are often 6/6 at the age of four years and 6/5 at the age of six years.)

Low vision, visual acuity equal or less than one third of the mean visual acuity of normally sighted children at the same age and better than no perception of forms,

severe low vision, visual acuity equal or less than one tenth of visual acuity of normally sighted children at the same age,

profound low vision

: light perception with projection.; light perception without projection.

Total blindness, equal to no light perception

Visual acuity measured as grating acuity.
Since grating acuity measures brain functions different from those measured< with optotype acuity it cannot be used as a basis of classification of visual impairment which in adult persons is defined based on form perception, i.e. optotype acuity. Grating acuity may well be within the range of age normal values, yet central vision is not developing normally. Classification of children in whom only grating acuity can be measured is based on their overall ability to use vision for development. Classification of infants is based on the presence or absence of visual functions typical to that age.
Visual acuity at near
In children visual acuity at near is more important a measurement than that of distance visual acuity because learning mostly occurs at close distances and in infants also communication is a near vision function. Visual acuity is measured using line tests, single symbol tests and crowded tests to assess the ability of the visual pathways to handle crowding.
Contrast sensitivity is measured using age appropriate tests. In children who can respond in an optotype tests, low vision is defined similar to adult persons. In assessment of vision of infants and young children standardised fixation targets at 2.5% contrast are used and the greatest distance where the infant responds to the stimulus is measured.

Normal vision is defined as responses at a distance greater than one third of the mean distance of responding of normally developing infants/children at the same age (age norms to be agreed upon)

Low vision is defined as responses at a distance equal or less than one third of the mean distance of responding of normally developing infants/children at the same age,

: severe low vision is defined as responses at a distance equal or less than one tenth of the mean distance of responding of normally developing infants/children.
In case contrast sensitivity is more affected than visual acuity, classification is based on contrast sensitivity loss.

Visual field, colour vision, motion detection and discrimination and visual adaptation are assessed similar to the assessment of adult persons using age appropriate tests.