Abstract
Purpose: :
Recent reports have indicated that disruption of the photoreceptor outer segments may be visible with high resolution 3D Fourier domain OCT (3D-OCT) yet may not be visible with time domain OCT (TD-OCT). To study this question, we compared the detection of photoreceptor outer segment disruption (POSD) with TD-OCT to detection with 3D-OCT.
Methods: :
3D-OCT scans (128 x 512) were obtained using a Fourier domain OCT instrument (3D-OCT-1000, Topcon, Japan) in 50 eyes of 28 consecutive patients undergoing simultaneous conventional time-domain (6 x 512) StratusOCT (ver. 4.0, Carl Zeiss Meditec, CA) for various diagnoses in a tertiary retina practice. Two graders reviewed each set of scans in an independent, masked fashion specifically identifying the inner segment - outer segment (IS-OS) junction. Photoreceptor outer segment discontinuities (POSD) were graded as "present," "absent," "questionable" or "can't grade." Discrepancies between graders were adjudicated. For purposes of analysis, findings still deemed as questionable after adjudication were considered as "present." The ground truth for each case was determined by merging the findings from both methods to generate the maximal possible level of detection for each finding.
Results: :
POSD was detected in a total of 15 out of 50 eyes (30%). TD-OCT detected POSD in 6/15 scans (40%) while 3D-OCT detected POSD in 14/15 scans (93%). TD-OCT detected POSD in 1 case (7%) where 3D-OCT failed to detect it. 3D-OCT detected POSD in 8 cases (53%) where TD-OCT failed to detect it. Using the combined findings as the ground truth, the overall sensitivity of TD-OCT for detection of POSD was 40% while the sensitivity of 3D-OCT was 93%.
Conclusions: :
3D-OCT is more sensitive than TD-OCT for detection of photoreceptor outer segment disruption. Our results verify other reports that high resolution OCT demonstrates this finding more reliably. Posterior outer segment disruption may explain visual symptoms in some patients with otherwise unexplained visual loss.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • photoreceptors • imaging/image analysis: clinical