Visual assessment of the multiply handicapped patient.

The visual capabilities of the multiply handicapped and/or developmentally delayed patient are difficult to assess with methods that depend on the patient's subjective responses. Fifty-nine patients with multiple neurological handicaps and unknown visual capabilities were examined using a modified ophthalmic examination which included visual acuity measures using visual evoked potential (VEP) and preferential looking (PL) techniques. Patients ranged in age from 3 to 33 years; median age 9 years. Significant refractive error (in 73%) and strabismus (in 71%) were the most common ocular disorders. Of the 43 patients with a significant refractive error, only 16 (37%) were wearing their proper correction (ranging from -21 to +20 D). In 27 patients the uncorrected refractive error ranged from -10 to +20 D. Binocular acuities (with refractive correction) could be obtained from 56 patients (95%) using a spatial frequency sweep VEP technique, and in 41 patients (70%) using PL grating acuity cards. The VEP and PL grating acuity measures agreed to within 1 octave (a factor of 2 in minimum angle of resolution) in 27 of 41 patients. VEP acuity was 1.1 to 2.7 octaves higher in 12 patients. Grating acuity of at least 6/12 (20/40) was estimated in 12 patients. Residual vision can be measured in "difficult to examine" multiply handicapped patients with VEP and PL techniques.