Measurement of potential visual acuity in 343 patients with cataracts. A prospective clinical study.

In 343 patients with cataracts (the largest consecutive series in which this subject has been addressed) and 63 patients with clear optic media, who served as the control group, potential visual acuity was measured with the Guyton/Minkowski Potential Acuity Meter (PAM). The control group included 32 cases of macular degeneration, 22 cases of glaucoma, and 9 cases of amblyopia. The cataract group comprised 46 patients with macular degeneration, 46 with glaucoma, and 8 with amblyopia; 5-7 days postoperatively, corrected visual acuity was measured in this group. Because of dense cataracts in 59 patients, no PAM value could be obtained. The visual acuity of 70.4% of the patients, in whom complete data were obtained, was within one Snellen line of the predicted value or better (21%). In general, postoperative predictions were accurate in patients with moderate cataracts. The results were not affected by glaucoma or amblyopia. In 17.5% of patients with macular degeneration, false-positive results were obtained. The control group, in which distance visual acuity was compared with the PAM values, rendered comparable results, with 86.9% of the PAM predictions being correct.