Dynamic soft drusen remodelling in age-related macular degeneration

Aims To demonstrate and quantify the dynamic remodelling process of soft drusen resorption and new drusen formation in age-related macular degeneration (AMD) with novel interactive methods. Methods Twenty patients with large soft drusen bilaterally and without advanced AMD were imaged at baseline and again at a mean interval of 2 years (40 eyes, 80 images). Each of the 40 serial pairs of images was precisely registered by an automated technique. The drusen were segmented by a user-interactive method based on a background levelling algorithm and classified into three groups: new drusen (only in the final image), resorbed drusen (present initially but not in the final image) and stable drusen (present in both images). We measured each of these classes as well as the absolute change in drusen broken vertical bar D1 - D0 broken vertical bar and the dynamic drusen activity (creation and resorption) D(new) + D(resorbed). Results Mean dynamic activity for the right eye (OD) was 7.33 +/- 5.50%, significantly greater than mean absolute change (2.71 +/- 2.89%, p=0.0002, t test), with similar results for the left eye (OS). However, dynamic activity OD compared with OS (mean 7.33 +/- 5.50 vs 7.91 +/- 4.16%, NS) and absolute net change OD versus OS (2.71 +/- 2.89 vs 3.46 +/- 3.97%, NS) tended to be symmetrical between fellow eyes. Conclusions Dynamic remodelling processes of drusen resorption and new drusen formation are distinct disease activities that can occur simultaneously and are not captured by change in total drusen load. Dynamic changes occur at rates more than twice that of net changes, and may be a useful marker of disease activity.