Displacement threshold hyperacuity as a predictor of postsurgical visual performance in patients with cataract.

ABSTRACT

PURPOSE: To evaluate the ability of Displacement Threshold Hyperacuity (DTH) in predicting the postoperative visual outcome in patients awaiting cataract surgery and discriminating between the relative performance of the neural and optical components of the visual system. To establish eventually the cut-off DTH values to be used clinically in the preoperative evaluation of patients with cataract. METHODS: Forty-five subjects admitted for extracapsular cataract extraction with implant were examined preoperatively and postoperatively. In addition to DTH, logMAR visual acuity (VA), contrast sensitivity, and a cataract classification system were used to obtain a more comprehensive assessment of the patient's visual performance. RESULTS: DTH was found to be sensitive to decreased macular function but relatively unaffected by the severity of the cataract; higher thresholds were associated with denser opacities. A preoperative threshold of 50 seconds of arc was found to be the upper limit under which normal macular function is likely. DTH sensitivity and specificity for decreased macular function was 1.00 and 0.8, respectively. CONCLUSIONS: If preoperative DTH is 50 seconds of arc or lower, the subject will achieve a postoperative logMAR VA better than 0.3 (Snellen equivalent 20/40). On the contrary, higher DTH seems to give no reliable information about the patient's visual function.