Predicting visual acuity after cataract surgery using the blue field entoptoscope and projected slides

A new method allows accurate testing of visual function behind mild-to-moderate cataracts or capsular opacities. Patients were asked to compare the number of corpuscles visualized with the blue field entoptoscope with a series of projected slides having progressively fewer drawn corpuscles. To standardize the equipment, the test was performed on 69 patients with varying degrees of macular impairment. Of the patients who selected 120 corpuscles or more, 89% had visual acuities of 20/40 or better, and those who selected 100 corpuscles or less, 82% had visual acuities of 20/50 or worse. The percentages were higher for age-related macular degeneration (ARMD) patients (100 and 85%) than for diabetic patients (33 and 75%). The same apparatus was then used to predict the potential visual acuity in 56 preoperative cataract or YAG-capsulotomy patients. Of the 23 patients with a preoperative acuity of 20/200 or better and who selected 120 corpuscles or more, 100% were 20/40 or better postoperatively.