The study was designed as a replication of a study reported in this Journal (Miller S [1989] Optical differences in cases of multiple personality disorder. J. Nerv Ment Dis 177:480-486) which found that subjects with multiple personality disorder (MPD) experienced significantly more changes in visual functioning between alter personalities than a control group simulating the disorder. In the present study, data from 20 patients diagnosed with MPD and 20 control subjects role playing MPD were analyzed for statistical and clinical significance. The findings from the present study appear to confirm results from the earlier study that individuals with MPD experience differences in some aspects of visual functioning between alter personalities. The results further confirm that MPD subjects experience more differences across visual measures than control subjects simulating the disorder. However, the findings from the present study are not entirely consistent across the various visual measures or with findings from previous studies.