Spectral Domain Optical Coherence Tomography Imaging of Geographic Atrophy Margins

Objective: To test in vivo whether spectral domain optical coherence tomography (SD-OCT) provides adequate resolution for reproducible measurement of photoreceptor (PR) layer at the margins of geographic atrophy (GA), and if it delineates the relationship between PR layer and retinal pigment epithelium at the margins of GA. Design: Prospective consecutive case series. Participants: Patients with GA secondary to nonneovascular age-related macular degeneration (AMD) identified during routine follow-up at Duke Eye Center between January 3, 2006, and June 3, 2007, and who consented to participate in this study. Methods: We used SD-OCT to image eyes. Multiple B-scans from each eye were saved and independently graded by 2 graders and the following locations were marked: (1) site where PR thickness began to decline below its baseline, (2) site where PR layer disappeared, and (3) site of the GA margin. These data were processed to calculate the locations of PR losses relative to GA margins and were categorized as (A) bridging across GA margins, (13) entirely within GA margins, or (C) entirely outside GA margins. Main Outcome Measures: Location of PR loss (bridging across GA margins, entirely within GA margins, or entirely outside GA margins) was calculated. Distances from the GA margin were measured for beginning and ending of PR loss. Interobserver agreement was determined for categories of PR loss as well as locations of PR loss relative to the GA margin. Results: We analyzed 500 unique scans. The PR loss occurred most frequently bridging across the GA margin (65% scans), second most frequently entirely inside the GA margin (29% scans), and least frequently entirely outside the GA margin (6% scans). Loss of PR started an average of 61 mu m (standard deviation [SD] +/- 235) outside the GA margin, ended an average of 311 +/- 273 mu m inside the GA margin, and spanned an average of 372 +/- 179 mu m. Conclusions: Relative to GA margins in nonneovascular AMD with GA, SD-OCT provides adequate resolution for quantifying PR loss. It may also serve as a means of tracking disease progression in future interventional trials.