Assessment of visual acuity in multiply handicapped children.

Assessment and management of visual disorders in children with physical and/or intellectual impairment present a complex challenge to the clinician. A comprehensive review of all aspects of vision care in multiply handicapped children is too diverse to address in a single review. This review will focus on the techniques which have been developed for visual acuity assessment in this challenging population. Conventional acuity tests are often impractical and unsuccessful for achieving a reliable measurement of visual acuity in multiply handicapped children.' Two visual acuity assessment techniques have gained wide acceptance for testing these children, preferential looking (PL) and visual evoked potentials (VEPs). The success rates of completion of these procedures and acuity estimates achieved are compared and discussed. Multiply handicapped children have a high incidence of nearly all types of disorders affecting the visual system including refractive errors, strabismus, nystagmus, cataract, optic atrophy, optic nerve hypoplasia, defects of the visual field, and cortical blindness.2-9 Reported prevalence of visual disorders for different groups of handicapped children is summarised in Table 1. Prevalence for each condition varies widely as studies are based on different populations of handicapped children and different criteria were used to establish the diagnoses. These conditions are not mutually exclusive for example, 80-86% of children with cerebral palsy have one or more of the above visual disorders.9 10