2.1. SCREENING AND CLASSIFICATION OF VISUALLY IMPAIRED CHILDREN

In the developed countries, screening and classification of vision impairment and disability in pre-school and school children comprise part of public or private health services. Vision screening at school is primarily designed to detect children who need glasses. At school age, new cases of vision impairment are usually detected by teachers or parents because of a change in the child's daily functioning, rarely by screening.

The level of visual acuity is often used as the basis of classification. The Colenbrander "Functional Acuity Score" lists five groups: moderate, severe and profound low vision, and near-total and total impairment. Classification of impairment in this way is useful for planning prevention of blindness programs. However, for education and (re)habilitation the functional abilities and disabilities, now referred to as "activities" in the ICF, warrant classification. For educational purposes five different groups of visually impaired children (I a & b - IV) are described according to function:

Ia     No Light Perception
Ib     Light Perception without Projection
II     Light Perception with Projection
III     Form Perception with Visual Acuity (VA) <0.05 (3/60, 20/400)
IV     Visual Acuity = or > 0.05 (3/60, 20/400)
V     "Normally" Sighted, i.e. children with impairment who do not need low vision services

Children in Groups I - II use the techniques of blind people for all their functions, but have individual differences in their abilities depending on how well they can use vision for orientation (Group II).

Children in Group III use techniques of blind people in many areas of learning but can also use vision assisted by optical and non-optical devices for high magnification, where these are available. Many of these children can effectively use their vision for both orientation and mobility and when learning daily living skills and social interaction.

Children in Group IV are functionally very different, although they are all classified as having moderate to severe low vision. The borderline between Group IV and Group V is difficult to draw. The <0.32 (6/18, 20/63)-line, used in international reporting of vision impairment, cannot be applied as a dividing line for education and intervention. At approximately the level of 0.05 (3/60, 20/400) and better, visual acuity alone does not depict visual function of the child, below that it roughly depicts visual capability in sustained near vision tasks. A visual acuity of 0.2 (6/30, 20/100) may mean near normal visual function if the loss of visual acuity is caused by a condition in which visual field, contrast sensitivity and colour vision are normal (e.g. x-linked retinoschisis). On the other hand visual acuity may be better than 0.32 (6/19, 20/63), yet the child may need low vision services because of poor image quality, night blindness or oculomotor problems.

In Kenya, a closely similar classification of children with low vision, based on their educational medium, has been used . After the individual assessments that cover refraction, visual acuity at distance and near, oculomotor functions and fitting of optical and non-optical low vision devices, following groups in terms of educational needs emerge: Children who can use print as their educational medium and those who need to use Braille. The groups were further divided in educational categories:

  • Category I, totally blind children, Braille users
  • Category II, some useful vision but not enough to read print, thus Braille users
  • Category III, print reading with optical devices
  • Category IV, print reading with geometric magnification and other special techniques

There are also children whose vision is close to normal or normal but who have not yet been able to move to regular schools - for various reasons. They are the

  • Category V, children with no need of special education services.

These categories have been in use since 1995 and are very useful when explaining the educational needs of children with vision impairment.

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