Inter-eye Asymmetry in Retinal Nerve Fiber Layer Thinning for Subtypes of Open Angle Glaucoma

Abstract

Purpose : To assess the inter-eye asymmetry in retinal nerve fiber layer (RNFL) thinning for four different subtypes of open angle glaucoma (OAG): primary OAG (POAG), normal tension glaucoma (NTG), pseudoexfoliation glaucoma (PXG), and pigmentary glaucoma (PDG), and to compare this with normal controls.

Methods : Spectral domain optical coherence tomography (SD-OCT) (Heidelberg Engineering, Heidelberg, Germany) was used to measure RNFL thickness from a peri-papillary circular scan pattern of approximately 3.5-3.6 mm in diameter for right and left eyes of 285 participants. Each patient signed the consent forms. Inter-eye asymmetry was analyzed for each group as well as quadrants and sectors using Pearson correlation coefficients (r).

Results : A total of 570 eyes of 285 participants [102 patients with POAG, 33 with NTG, 48 with PXG, 13 with PDG, and 89 patients without glaucoma] were included in this study. RNFL thinning between right and left eyes for 3 subtypes of OAG were significantly symmetric for global RNFL (i.e., POAG, NTG, and PDG groups with r values = 0.284, 0.707, and 0.785; and p values = 0.004, <0.0001, and 0.001; respectively) as well as the superior and inferior quadrants and sectors for the NTG and PDG groups (Table 1). PXG group showed inter-eye asymmetry for global RNFL thinning (r = 0.03, and p value = 0.838) as well as for the superior and inferior quadrants and sectors (r values = 0.014-0.337, and p values = 0.174-0.924). We also found inter-eye asymmetry for RNFL thinning in the inferior quadrant and inferior-temporal sector of POAG patients (r values = 0.146 and 0.168; and p values = 0.142 and 0.092; respectively).

Conclusions : This study suggests that SD-OCT may be able to detect inter-eye asymmetry in RNFL thinning for different subtypes of OAG. The PXG group may have inter-eye asymmetry in RNFL thinning globally, superiorly, and inferiorly. POAG patients may have more inter-eye asymmetry in the inferior and inferior-temporal regions compared to other regions.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Table 1: Correlation coefficients (r) for retinal nerve fiber layer thinning symmetry between right and left eyes in different subtypes of open angle glaucoma.
POAG = primary open angle glaucoma, NTG = normal tension glaucoma, PXG = pseudoexfoliation glaucoma, PDG = pigmentary glaucoma.
*P value < 0.05 is statistically significant. If the P value < 0.05 then the two eyes are more likely symmetric in RNFL thinning.