A Method of Drusen Measurement Based on the Geometry of Fundus Reflectance

BACKGROUND: The hallmarks of age-related macular degeneration, the leading cause of blindness in the developed world, are the subretinal deposits known as drusen. Drusen identification and measurement play a key role in clinical studies of this disease. Current manual methods of drusen measurement are laborious and subjective. Our purpose was to expedite clinical research with an accurate, reliable digital method. METHODS: An interactive semi-automated procedure was developed to level the macular background reflectance for the purpose of morphometric analysis of drusen. 12 color fundus photographs of patients with age-related macular degeneration and drusen were analyzed. After digitizing the photographs, the underlying background pattern in the green channel was leveled by an algorithm based on the elliptically concentric geometry of the reflectance in the normal macula: the gray scale values of all structures within defined elliptical boundaries were raised sequentially until a uniform background was obtained. Segmentation of drusen and area measurements in the central and middle subfields (1000 μm and 3000 μm diameters) were performed by uniform thresholds. Two observers using this interactive semi-automated software measured each image digitally. The mean digital measurements were compared to independent stereo fundus gradings by two expert graders (stereo Grader 1 estimated the drusen percentage in each of the 24 regions as falling into one of four standard broad ranges; stereo Grader 2 estimated drusen percentages in 1% to 5% intervals). RESULTS: The mean digital area measurements had a median standard deviation of 1.9%. The mean digital area measurements agreed with stereo Grader 1 in 22/24 cases. The 95% limits of agreement between the mean digital area measurements and the more precise stereo gradings of Grader 2 were -6.4 % to +6.8 % in the central subfield and -6.0 % to +4.5 % in the middle subfield. The mean absolute differences between the digital and stereo gradings 2 were 2.8 +/- 3.4% in the central subfield and 2.2 +/- 2.7% in the middle subfield. CONCLUSIONS: Semi-automated, supervised drusen measurements may be done reproducibly and accurately with adaptations of commercial software. This technique for macular image analysis has potential for use in clinical research

Prophylactic laser treatment of soft drusen maculopathy: a prospective, randomized Nordic study

Purpose: This study aimed to investigate whether mild laser treatment of soft drusen maculopathy might reduce the incidence of choroidal neovascularization (CNV) and/or significantly reduce loss of visual acuity compared with outcomes in a control group. Methods: A total of 135 patients (mean age 70.4 years) were randomized into a treatment group of 67 subjects and a control group of 68 subjects. The treatment group was subdivided into a group of 54 subjects with bilateral soft drusen and a group of 13 subjects with unilateral soft drusen in the study eye and advanced AMD in the fellow eye. The control group was subdivided into a bilateral group of 54 subjects and a unilateral group of 14 subjects. Sub-threshold or barely visible laser spots were scattered on and between drusen in the posterior pole. Inclusion of patients was stopped prematurely as other studies did not show any benefit from the treatment. Mean follow-up time was 3.7 years. Results: More CNVs developed in the treated group (4/54 eyes in the bilateral group, 3/13 eyes in the unilateral group; 7/67 eyes in total) than in the control group (3/54 eyes in the bilateral group, 2/14 eyes in the unilateral group; 5/68 eyes in total) but these differences were not statistically significant for either the bilateral or unilateral groups (p = 0.20-0.32). No CNV developed in the bilateral treated group before 4 years of follow-up. Visual acuity was significantly reduced from baseline to the last follow-up in all groups (p andlt; 0.0001-0.02) except the unilateral control group (p = 0.08), but there were no significant differences between the treated and control groups for either the bilateral or unilateral groups (p = 0.17-0.97). Conclusions: Mild prophylactic laser treatment of soft drusen maculopathy was neither beneficial nor harmful and cannot be recommended.</p