Peripapillary choroidal thickness in primary open angle glaucoma and normal subjects measured by enhanced depth imaging optical coherence tomography

Abstract

To compare peripapillary choroidal thickness (CT) between primary open angle glaucoma (POAG) and normal subjects using enhanced depth imaging optical coherence tomography (EDI-OCT). This research was a cross-sectional study. A 360-degree 3.4 mm diameter peripapillary circle scan was performed for retinal nerve fiber layer (RNFL) assessment by EDI-OCT in one eye of 40 POAG patients and 41 age- and sex-matched normal subjects. The observer used the manual segmentation function to delineate the posterior edge of the retinal pigment epithelium and the sclerochoroidal interface. The RNFL thickness algorithm function was used to automatically generate the CT in corresponding sectors. The intra- and inter-observer reproducibility was evaluated by intraclass correlation coefficient (ICC). Repeated measures ANOVA and LSD-t test were used to analyze differences in CT by peripapillary location. A Pearson correlation was calculated for variation in CT relative to age and RNFL. Spearman rank correlation was calculated to test the strength of the relationship between global mean RNFL and visual field mean deviation (MD) and between CT and MD. Independent-samples t-test was conducted to compare mean RNFL and CT between POAG and normal subjects. The intra- and interobserver ICC values ranged from 0.993 to 0.999 and 0.993 to 0.998 respectively. In both groups, the CT showed a negative correlation with age at each peripapillary location (r = -0.509 to -0.608, -0.549 to -0.668; P = 0.000 to 0.001) but no significant correlation with RNFL for any location (r = -0.186 to 0.273, -0.090 to 0.132; P = 0.092 to 0.869). The peripapillary CT was thickest superotemporally and superonasal, then nasally and temporally, and was thinnest inferotemporally and inferonasal (P = 0.000 to 0.036). Compared to normal subjects, eyes with POAG had significantly thinner RNFL at all locations (t = 6.975 to 16.087, P = 0.000), but CT measurements did not differ between groups for any location (t = -0.474 to 0.367, P = 0.637 to 0.978). In POAG patients, the global mean RNFL (rs = -0.511, P = 0.001) but not CT (rs = -0.285, P = 0.079) was found to significantly correlate with visual field MD. The peripapillary CT in POAG neither differ from that in normal subjects nor correlate with RNFL and visual field index, which does not support using it as a clinical parameter in glaucoma diagnosis or management.