DISPLACEMENT THRESHOLD HYPERACUITY AS A PREDICTOR OF POSTSURGICAL VISUAL PERFORMANCE IN PATIENTS WITH CATARACT

Purpose. To evaluate the ability of Displacement Threshold Hyperacuity (DTH) in predicting the postoperative visual outcome in patients awai ting cataract surgery and discriminating between the relative performa nce of the neural and optical components of the visual system. To esta blish eventually the cut-off DTH values to be used clinically in the p reoperative evaluation of patients with cataract. Methods. Forty-five subjects admitted for extracapsular cataract extraction with implant w ere examined preoperatively and postoperatively. In addition to DTH, l ogMAR visual acuity (VA), contrast sensitivity, and a cataract classif ication system were used to obtain a more comprehensive assessment of the patient's visual performance. Results. DTH was found to be sensiti ve to decreased macular function but relatively unaffected by the seve rity of the cataract; higher thresholds were associated with denser op acities. A preoperative threshold of 50 seconds of are was found to be the upper limit under which normal macular function is likely. DTH se nsitivity and specificity for decreased macular function was 1.00 and 0.8, respectively. Conclusions. If preoperative DTH is 50 seconds of a re or lower, the subject will achieve a postoperative logMAR VA better than 0.3 (Snellen equivalent 20/40). On the contrary, higher DTH seem s to give no reliable information about the patient's visual function.