Are Patients With Diabetes Less Likely to Develop Age–Related Macular Degeneration if Panretinal Photocoagulation Was Performed? Follow Up to the Biomechanical Shell Model Hypothesis

Abstract

Abstract: : Purpose: To determine if a history of panretinal photocoagulation (PRP) is associated with fewer cases of physician diagnosed dry age–related macular degeneration (ARMD) in patients with diabetes. Methods: A retrospective chart review was performed on approximately 600 charts from patients with diabetes in a University based Retina practice. All patients underwent complete eye exam including visual acuity testing, anterior segment examination, and a dilated posterior segment examination by fellowship trained Retina specialists. Inclusion criteria were patients with diabetes (Type 1 or Type 2) older than 55 years who had at least 6 months of follow–up. Patients with PRP had to have at least six months of follow up after the laser was performed to be included in the analysis. Patients who had focal macular laser (FML) were not excluded. The diagnosis of ARMD was made by observation of drusen or geographic atrophy in the posterior pole. Results: In our study there were 797 eyes. 119 of the eyes had dry ARMD. Of those eyes with dry ARMD, 22 had PRP, 97 had not had PRP. 678 eyes did not have ARMD. 161 of those eyes had PRP while 517 had not had PRP. Mean follow up time after PRP was 4.6 years. We utilized logistic regression analysis with the dependent binary variable ARMD and explanatory variables PRP, with and without Race and FML. We calculated the odds ratio of developing ARMD in those patients with PRP at 0.60 (p=0.134) when compared to patients without PRP. When controlling for race and FML, there was no effect of PRP. Conclusions: In a previous ARVO abstract we proposed that constraining the retina around the periphery with PRP alters the mechanical stress distribution of the posterior pole based on a shell model. We hypothesized that this decreased mechanical stress on Bruch’s membrane may correlate with a decreased incidence of ARMD by decreasing microfragmentation of Bruch's membrane. In this current retrospective study, PRP does not appear to have a significant effect on the development of ARMD. However, we do recognize the inherent weaknesses with such a study and a relatively small sample size. Further investigation is warranted looking at intensity and pattern of laser applied as well as a larger sample size.

Keywords: age-related macular degeneration • diabetes • laser