Abstract
Purpose: :
To compare an automated algorithm for evaluation of optic discs imaged by spectral domain optical coherence tomography (SD-OCT) to stereoscopic observation of photos.
Methods: :
Stereo photos were obtained of the optic disc of 149 eyes. Independently, 3 observers traced the disc and of the cup margins using a digitizing touch-screen monitor. SD-OCT images were obtained with the CirrusTM HD-OCT (Carl Zeiss Meditec, Inc., Dublin, CA) and analyzed with an automated algorithm (CirrusTM software release 5.0).
Results: :
The mean area of the discs in photos was 2.20, 2.13, and 2.02 mm2 by three readers. The opening in Bruch's membrane by OCT had a mean area of 1.82 mm2. The cup areas were 0.57, 0.47, and 0.70 mm2 in photos, and 0.62 mm2 by the OCT. The rim areas were 1.63, 1.66, 1.32 mm2 in photos, and 1.20 mm2 by OCT. Thus, the cup areas by photos and OCT were about the same; but a smaller disc area made the rim about 0.3 mm2 smaller by OCT.The mean differences of cup/disc area ratios between reader pairs were 0.095, 0.131, and 0.161. The mean differences of OCT with the three readers were 0.136, 0.162, and 0.095. The OCT thus differed from photo readings as much as two photo readers differed from each other.For between-reader agreements, intraclass correlation coefficients (ICCs) were 0.67 to 0.86, 0.77 to 0.88 and 0.39 to 0.66 for disc, cup and rim areas. ICCs for agreement of the OCT with the mean of photo readings were similar, 0.7, 0.9, and 0.4 for disc, cup, and rim areas.For within-reader reproducibility, ICCs were 0.80 to 0.86 for the rim, but 0.95 to 0.98 for disc and cup areas. Reproducibility of the OCT gave an ICC of 0.96 to >0.99 for all three areas.
Conclusions: :
The disc area in OCT (area of the opening in Bruch’s membrane) is somewhat smaller than the area determined by landmarks seen in fundus photographs. With the cup size being the same, the rim area is likewise smaller by OCT. Readers of photographs varied among themselves. They showed excellent consistency with their own previous readings, but OCT gave even better reproducibility.
Keywords: optic disc • imaging/image analysis: clinical