The clinical effect of detecting visual field loss was studied in 66 patients with visual field defects. Fifty-two percent of defects were the result of conditions which were themselves considered to be significant. Visual field results were considered to have made vital and important contributions to that diagnosis in 28% and 23% of cases, respectively. The results also brought about a change in the intended management strategy in 39% of cases, but were also helpful in another 35% of cases. It was concluded that the clinical importance of regular perimetric examination is emphasized by these results, which may in turn contribute to the detection of unexpected visual field defects.