Purpose: The Drusen Laser Study (DLS) of high-risk age-related maculopathy (ARM) is a randomised, controlled clinical trial designed to answer two questions: (1). Do drusen resolve after macular laser photocoagulation (2). Does macular laser photocoagulation prevent choroidal neovascularisation (CNV) in high-risk eyes? In this report, we present the results of the interim, pooled analysis of CNV prophylaxis for patients in the Unilateral Group of the DLS.
Methods: The DLS is a randomised controlled clinical trial of prophylactic macular photocoagulation for high-risk ARM. Patients in the Unilateral Group had a neovascular complication in the first eye; their fellow eye (Study Eye) had visual acuity of 6/12 or better and drusen. Following informed consent, patients were randomised to the Treatment Group or the No Treatment Group. Patients randomised to treatment received 12 light spots of argon laser photocoagulation to their Study Eye: four burns were placed 750 microm from the centre of the fovea at 12, 3, 6, and 9 o'clock, and the eight remaining burns were placed 1500 microm from the centre of the fovea at 12, 1:30, 3, 4:30, 6, 7:30, 9, and 10:30 o'clock. Drusen were treated directly only if they were present at the protocol treatment locations. All patients were followed in an identical fashion at regular intervals. Best-corrected visual acuity was measured and recorded by a masked observer. Fluorescein angiography was performed at baseline and yearly review, as well as nonprotocol visits if symptoms suggested CNV. Five clinical centres utilised and conformed to a common DLS protocol. Patient care and data collection methodologies were deemed sufficiently similar to permit a pooled data analysis.
Results: There were 156 patients included in the interim analysis, and timed information was available on 153. CNV occurred in 21 of 81 (26%) patients in the Treatment Group and in 13 of 75 (17%) patients in the No Treatment Group (P=0.19). Kaplan-Meier survival analysis showed earlier onset of CNV in the Treatment Group compared to patients in the No Treatment Group (statistical significance not calculated). Visual acuity loss at 2 years occurred in nine of 54 (17%) patients in the Treatment Group compared to the two of 48 (4%) patients in the No Treatment Group (P=0.056).
Conclusions: We are only the second group to identify possible laser-induced CNV despite other similar studies in progress. Equipoise of the DLS investigators was lost, and recruitment was halted. We feel ethically bound to notify the ophthalmic community of this finding.