Changes in macular drusen parameters preceding the development of neovascular age-related macular degeneration

To assess the rate of change in macular drusen load in fellow eyes of patients with unilateral neovascular age-related macular degeneration (AMD) to evaluate whether the change in drusen load determines the onset and type of choroidal neovascularisation (CNV).

Subjects with unilateral neovascular AMD with a minimum of 2 years follow-up were identified retrospectively from the hospital electronic database. Drusen count, area and volume measurements at the macula of the contralateral eye were recorded using the commercial software on the Topcon 3D OCT-2000 devices over the previous 2 years. The mean rate of change of these parameters over time was compared between fellow eyes that converted to various CNV subtypes and those that did not.

Two hundred forty-eight patients met the inclusion criteria. Of these patients, 179 patients did not progress to neovascular AMD (Group 1) while 69 patients converted (Group 2) at the end of 2 years follow up. Mean drusen volumes and drusen areas increased significantly in Group 2 in the 2nd year by 0.031 mm³ (p < 0.001) and 0.572 mm² (p = 0.002), respectively. However, there was no difference in the rate of change between the two groups at year 1. Furthermore, for each 0.1 mm increase in the cubed root of baseline mean drusen volume increases the odds of progressing to CNV by 40% (95% CI 1.2-1.6; p < 0.001). The increase in drusen volume was higher in the occult CNV group compared to classic CNV (p = 0.048).

A significant increase in mean drusen volume occurs in eyes in the preceding 12 months prior to conversion to neovascular AMD and this change is more significant in eyes with occult CNV.