CLINICAL COMPARISON OF 3 TECHNIQUES FOR EVALUATING VISUAL FUNCTION BEHIND CATARACT

The aim of the study was to compare the ability of displacement thresh old hyperacuity to identify reduced retinal/neural function in catarac t patients with that of the potential acuity meter (PAM) and laser int erferometer. Fifty-two patients (mean age 72.0 +/- 10.8 years) admitte d for extracapsular cataract extraction were randomly selected for inc lusion in the study. Patients underwent routine refraction and logMAR acuity measurement on the eve of cataract surgery. Following pupillary dilation and in random order, the oscillatory displacement threshold (ODT; defined as the smallest detectable displacement of an object) wa s determined, and predictions of the post-operative acuity were obtain ed using the PAM and Rodenstock Retinometer (RR). Patients were re-exa mined approximately 7 weeks post-operatively when logMAR acuities acid ODTs were remeasured, On the basis of the results of an independent f undus examination, patients were assigned to either a normal or a path ology group. Increasing cataract density adversely affected the predic tions provided by the PAM (p = 0.0001) and ODT (p = 0.0001) techniques , but not the RR (p = 0.137). One-factor ANOVA revealed that pre-opera tive ODT (p = 0.0001), PAM (p = 0.0001) and RR (p = 0.0004) measures s uccessfully distinguished patients with retinal/neural pathology from normals. Preoperative cut-off levels to distinguish normal from pathol ogy cases were retrospectively determined for each technique. The cut- off values for the PAM and ODT techniques yielded higher sensitivity a nd specificity values than was the case for the RR, The results sugges t that the predictive abilities of the PAM and ODT techniques are simi lar, and superior to that of the RR, Further work involving larger num bers of patients with posterior segment pathology is necessary to reve al which technique provides the best means of assessing retinal/nueura l function in the presence of ocular media opacities.