Effects of Quality Differences in Spectral Domain OCT on Glaucoma Diagnostics

Abstract

Purpose: : To examine whether differences in quality of spectral domain (SD) optical coherence tomography (OCT) images affect the diagnostic ability in glaucoma.

Methods: : One eye in each of 117 healthy subjects and 84 glaucoma patients were included. The median field MD was -10.69 (-31.54 to -0.07) dB in the glaucoma patients. The peripapillary retinal nerve fiber layer (RNFL) thickness was assessed by the extracted circle data of the SD/Cirrus high definition (HD) OCT 200x200 optic disc cube scan. Two OCT images per eye were acquired in one session; one image with the acquisition settings controlled by the commercial software and the other manually controlled. OCT image quality was estimated by the signal strength (SS). In participants with a difference in SS between images the sensitivity and specificity was compared between the images with the better and worse SS and evaluated for full circle, ≥ 1 quadrant, and ≥ 1 clock hour OCT average RNFL thickness below the 5^th percentile.

Results: : There was a difference in SS in 71 of the healthy subjects and in 46 of the glaucoma patients, 89% differed by 1 step better and 11% by 2 steps better on the SS scale. The RNFL thickness was on the average 1.4 microns thicker (p<0.0001) in the images with the better SS. The diagnostic sensitivity was not affected significantly by image quality, but specificity was 11% (CI95: 3 to 20%) better when applying the criterion of ≥ 1 clock hour below the 5^th percentile.

Conclusions: : The results suggest that small quality differences in SD OCT images have a significant effect on diagnostic performance.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • nerve fiber layer • optic nerve