Cataract Surgery Is Associated with a Higher Rate of Photodynamic Therapy for Age-Related Macular Degeneration

Purpose: To investigate the association between cataract surgery and the rate of photodynamic therapy (PDT) for age-related macular degeneration (AMD). Design: Observational population-based retrospective case-control study. Participants: All members in a district of the largest health maintenance organization (HMO) in Israel > 50 years old on January 1, 2001, who did not terminate their membership through May 31, 2005 (139 894 members). Methods: All PDT procedures for AMD performed in the study population between January 1, 2001 and May 31, 2005 (283 patients) and all cataract surgeries performed between January 1, 2001 and December 31, 2003 (5913 patients) were documented. We extracted clinical information from the chronic disease registry of the HMO as well as demographic and socioeconomic information. For each patient that underwent cataract surgery, 5 HMO members matched in age, gender, chronic diseases (systemic hypertension, diabetes, hyperlipemia, and ischemic heart disease), place of residence, country of birth and socioeconomic status, who did not undergo cataract surgery, were randomly chosen as controls (n = 29 565). Main Outcome Measures: The rate for undergoing PDT at different time periods after cataract surgery. Results: Fifty (0.85%) cataract patients and 94 control cases (0.32%) underwent PDT after cataract surgery (P<0.0001, chi-square test). A significant rise in PDT rate was noticed in cataract patients compared to controls during the first 6 months after surgery (P = 0.004, chi-square test). Between 6 and 12 months postoperatively, the PDT rates were similar in both groups. However, a more significant rise in PDT rates occurred between 1 and 1.5 years after surgery (P<0.0001, chi-square test). The Kaplan-Meier PDT-free survival curve of cataract patients was significantly worse than that of the controls (P<0.0001, chi-square test; P = 33.7, log-rank test). The hazard ratio for cataract patients compared to controls to undergo PDT after surgery was 2.7 (confidence interval = 2.4-5.7). The most significant factors to reduce the time to PDT were advanced age followed by having had cataract surgery, place of birth, socioeconomic status, and hyperlipidemia (Cox proportional hazards survival regression). Conclusions: We identified an increased rate of PDT, presumably for subfoveal AMD, 1 to 1.5 years after cataract surgery.