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
Functions of the internal musculature of the eye
incl. accommodation/ pupillary reflex to light and to convergence
- voluntary eye movements of the eyes
- tracking movements of the eyes
- saccadic movements of the eyes
- fixation 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
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
- 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
- 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.