The effect of neodymium : YAG capsulotomy on contrast sensitivity and the evaluation of methods for its assessment

Objective: To determine the most appropriate method for measuring the effec t on contrast sensitivity of neodymium:YAG (Nd:YAG) posterior capsulotomy f or early posterior capsular opacification (PCO). Design: Prospective comparison of five different methods for luminous contr ast sensitivity testing in patients undergoing capsulotomy, Participants: Sixteen patients with PCO involving the visual axis and visua l acuities of 20/40 or better were recruited sequentially. Intervention: All patients were tested with each of the five tests before a nd after Nd:YAG capsulotomy. Main Outcome Measures: The contrast sensitivity function was measured with variable contrast sine wave gratings using the Vistech VCTS 6500, Mentor B- VAT-II and a computer graphics system. Peak contrast sensitivity at 3 cyc/d eg was compared with two letter tests, the Pelli-Robson chart, and a comput er that generated optotypes. Results: Significant generalized improvement that was not frequency selecti ve was measured over the entire contrast sensitivity function after capsulo tomy, The five tests did not significantly differ (P > 0.05) in their measu rement of peak contrast sensitivity (3 cyc/deg) improvement after capsuloto my. Letter-based tests showed better agreement and lower variance than grat ings tests. Visual acuity and contrast sensitivity improvement were poorly correlated. Conclusions: This study shows that contrast sensitivity is adequately docum ented by a single measurement at 3 cyc/deg, is an informative supplement to visual acuity, and that little extra information is to be gained by measur ing further spatial frequencies in eyes with PCO. Peak contrast sensitivity is best determined using a letter-based test.