Detection of Localized Retinal Nerve Fiber Layer Defects in Glaucoma Using Enhanced Spectral-Domain Optical Coherence Tomography

Abstract

To compare retinal nerve fiber layer (RNFL) defects on fundus photographs with circumpapillary RNFL (cpRNFL) thinning or disruption on images obtained by speckle-noise-reduced spectral-domain optical coherence tomography (enhanced SD OCT), single-scan SD OCT, and single-scan time-domain OCT (TD OCT). Retrospective, comparative case series. Forty-four eyes of 44 patients with open-angle glaucoma with localized, wedge-shaped RNFL defects on red-free photographs and 35 normal eyes of 35 volunteers. Cross-sectional images of the cpRNFL and cpRNFL thinning, compared with the confidence interval limit of the normative database where the RNFL defect was photographically identified, were compared between the 3 types of OCT instruments: enhanced SD OCT (SD OCT with eye tracking and averaging of 16 images at the same location to reduce speckle noise; Spectralis HRA+OCT; Heidelberg Engineering, Heidelberg, Germany), single-scan SD OCT (RTVue-100; Optovue, Fremont, CA), and single-scan TD OCT (Stratus; Carl Zeiss-Meditec, Dublin, CA). Cross-sectional images of localized RNFL defects on red-free fundus photographs, sensitivity for detecting the photographic RNFL defect, and sensitivity and specificity for detecting glaucoma as having at least 1 abnormally thinned sector on the cpRNFL thickness map on OCT. Among the 44 eyes with glaucoma, 65 RNFL defects were identified on red-free fundus photographs. The cpRNFL boundaries were clearer on enhanced SD OCT images than on single-scan SD OCT or TD OCT images, particularly in regions corresponding to the RNFL defects. Enhanced SD OCT revealed various degrees of cpRNFL thinning, and disruption of cpRNFL reflectivity was seen in the same location as the photographic RNFL defect for 23 (35.4%) of the 65 RNFL defects. The RNFL defects were significantly less likely to be detected by single-scan TD OCT or SD OCT (P = 0.002 and P = 0.006, respectively) when the RNFL was not disrupted. Enhanced SD OCT was more sensitive in detecting the RNFL defects that were not disrupted compared with single-scan TD OCT (P<0.0001) or SD OCT (P<0.0001). Enhanced SD OCT had better sensitivity and specificity for detecting glaucoma compared with single-scan TD OCT or SD OCT (sensitivity, P = 0.006 and P = 0.001; specificity, P = 0.001 and P = 0.004, respectively). These results suggest that speckle-noise reduction can improve the detection of photographic RNFL defects in which cpRNFL reflectivity on OCT images is not disrupted. Proprietary or commercial disclosure may be found after the references.