Purpose
To investigate the prevalence of sectoral value differences due to segmentation errors in macular Ganglion cell-inner plexiform layer (GCIPL) scans using SD-OCT in glaucomatous and highly myopic eyes.
Methods
174 Cirrus HD-OCT macula scans were obtained from 77 patients. 96 eyes had high myopia (> -5D acuity) and were glaucoma suspects. 78 were defined as glaucomatous, having progressive visual field defects in more than one examination. GCIPL analysis was performed using the Cirrus 6.0 software and custom Septem retinal segmentation software. All thickness measurements were compared and sectors differing by more than 10 microns were manually reviewed by an expert observer. Cirrus review was performed on the instrument; Septem review using a Matlab GUI. A sector error was counted whenever either an error of more than 10 microns was seen.
Results
For Cirrus, 27 eyes (15.5%) reported at least one sector error. The Septem algorithm had only 6 such instances (3.4%). The chi-square test reports a significant difference in the prevalence of errors between the algorithms (p<0.001). Figure 1 shows example GCIP maps. Figure 2 shows their underlying segmentations.
Conclusions
The prevalence of errors in GCIP Cirrus thickness maps in the study is high (15.5%). Algorithms are improving, as is evidenced by the low error rate using Septem (3.4%). For current commercial devices, the emphasis on clinical judgment when assessing glaucomatous damage in such populations remains.
Keywords: 549 image processing •
550 imaging/image analysis: clinical •
605 myopia