Comparison of Drusen Area Detected by Spectral Domain Optical Coherence Tomography and Color Fundus Imaging

PURPOSE. To compare the measurements of drusen area from manual segmentation of color fundus photographs with those generated by an automated algorithm designed to detect elevations of the retinal pigment epithelium (RPE) on spectral domain optical coherence tomography (SD-OCT) images. METHODS. Fifty eyes with drusen secondary to nonexudative age-related macular degeneration were enrolled. All eyes were imaged with a high-definition OCT instrument using a 200 3 200 A-scan raster pattern covering a 6 mm X 6 mm area centered on the fovea. Digital color fundus images were taken on the same day. Drusen were traced manually on the fundus photos by graders at the Doheny Image Reading Center, whereas quantitative OCT measurements of drusen were obtained by using a fully automated algorithm. The color fundus images were registered to the OCT data set and measurements within corresponding 3- and 5-mm circles centered at the fovea were compared. RESULTS. The mean areas (+/- SD [range]) for the 3-mm circles were SD-OCT 1.57 (+/- 1.08 [0.03-4.44]); 3-mm color fundus 1.92 (+/- 1.08 [0.20-3.95]); 5-mm SD-OCT 2.12 (+/- 1.55 [0.03-5.40]); and 5-mm color fundus 3.38 (+/- 1.90 [0.39-7.49]). The mean differences between color images and the SD-OCT (color - SD-OCT) were 0.36 (+/- 0.93) (P = 0.008) for the 3-mm circle and 1.26 (+/- 1.38) (P < 0.001) for the 5-mm circle measurements. Intraclass correlation coefficients of agreements for 3-and 5-mm measurements were 0.599 and 0.540, respectively. CONCLUSIONS. There was only fair agreement between drusen area measurements obtained from SD-OCT images and color fundus photos. Drusen area measurements on color fundus images were larger than those with SD-OCT scans. This difference can be attributed to the fact that the OCT algorithm defines drusen in terms of RPE deformations above a certain threshold, and will not include small, flat drusen and subretinal drusenoid deposits. The two approaches provide complementary information about drusen.