Assessment of 12-month change in drusen volume on SD-OCT in dry Age Related Macular Degeneration

Abstract

Purpose : Drusen are one of the earliest signs of age-related macular degeneration (AMD), but the role of drusen in the progression of AMD is not completely understood. If drusen are involved in the progression to advanced AMD, a decrease in drusen volume could be a viable target for prevention therapy. The purpose of this study is to measure drusen volume in eyes at month 0 and month 12 to assess our ability to measure small, statistically significant changes in drusen volume over time.

Methods : SD-OCT macular cube images of 91 eyes with early or intermediate AMD were included. Eyes with 12-month follow-up and no progression to GA or neovascular AMD were included in the analysis. SD-OCT images were converted to a standardized Digital Imaging and Communications in Medicine (DICOM) format. Drusen volume was measured using a semi-automated algorithm developed at the University of Wisconsin’s Fundus Photograph Reading Center. The algorithm measures the volume of the RPE-drusen complex by calculating the area between the top of the drusen or RPE and Bruch’s membrane (see Figure 1). Total drusen volume in a 6 mm diameter circle centered at the fovea was measured at baseline and 12 months. Mean change in drusen volume was calculated, along with a 95% confidence interval for change in drusen volume. Two evaluators segmented 25 eyes to assess reproducibility.

Results : The mean drusen volume at baseline was 1.02 mm³ (± 0.17) and at month 12 1.06 mm³ (± 0.17). Mean change in drusen volume was 0.03 mm³ (± 0.04). There was no significant association between baseline drusen volume and mean change at 12 months (r -0.20, p 0.47); results did not change with cube root transformation. Inter-grader reproducibility data showed a mean difference of 0.02 mm³ (CI -0.02, 0.08) in drusen volume and 0.01 mm³ (CI -0.02, 0.05) for mean change in drusen volume.

Conclusions : The volume of the RPE-drusen complex on OCT images can be measured reproducibly. Though the majority of eyes showed an increase in drusen volume after 12 months, a minority of eyes showed no change or a decrease in drusen volume. This ability to accurately measure small changes in drusen volume over time could aid in development of new therapies for AMD.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Figure 1. OCT scan with segmentation lines denoting the top of the RPE-drusen complex (top) and Bruch’s membrane (bottom).