Using the Rate of Global and Pointwise Microperimetry Change to Predict Structural Conversion in Intermediate Age-Related Macular Degeneration

Purpose: Studies evaluating functional change in age-related macular degeneration (AMD) using microperimetry often measure the difference in global mean sensitivity at interval timepoints versus baseline.We evaluate the rate of global and pointwise microperimetry change in intermediate AMD (iAMD) in the multi-centre MACUSTAR study and assess their prognostic value in structural conversion to latestage AMD.Design: Prospective study Subjects: 447 subjects with iAMD (Beckman classification) from 20 European sites.Methods: Subjects that underwent mesopic microperimetry on at least three follow up visits were included.Two methods of assessing functional progression were evaluated.[1] global mean sensitivity regression,[2] pointwise sensitivity regression at fastest progressing N number of locations (N from one to ten).Rates of microperimetry progression were then evaluated in an initial series of visits prior to structural conversion to late-stage AMD.Main outcome measures: Area under the receiver operating characteristic (AUC) curves and Cox proportional hazard models were used to assess risk of structural conversion based on rate of functional progression.Results: Mean age of subjects was 72 (SD 7) years.The median number of visits and duration of follow up was six visits and three years respectively.Structural conversion to late-stage AMD was observed in 80 (17.9%) eyes.In the visits prior to conversion, there was a greater rate of global mean sensitivity loss in eyes that eventually developed late-stage AMD compared to those that did not (-1.05vs -0.30 dB/year, p < 0.001).The AUC for classifying structural conversion vs no conversion was 0.72 for global sensitivity progression, and 0.75-0.76for between 1 to 10 fastest progressing N pointwise locations.The rate of global [HR 1.7, confidence interval (CI) 1.4-2.0]and pointwise (HR 1.2, CI 1.2-1.3)microperimetry progression in the initial series of visits was significantly associated with structural conversion (p < 0.0001).Conclusions: In the analysis of longitudinal microperimetry data from the MACUSTAR study, the rate of global and pointwise sensitivity change was significantly greater and strongly prognostic of eyes that