Asymmetry of Peripapillary Retinal Blood Vessel Position and Thickness in Healthy Right and Left Eyes

Abstract

Purpose : There is considerable inter-individual and inter-eye variability in retinal nerve fibre layer thickness (RNFLT) measurements. Additionally, the position and thickness of retinal blood vessels (RBV) is related to RNFLT variability. We conducted this study to determine if there is asymmetry in RBV position and thickness between right and left eyes (R-L), and to determine if R-L asymmetry in RBV position explains most of the R-L asymmetry of RNFLT.

Methods : We used OCT data from a previous multi-centre study on healthy White subjects. Peripapillary circle scans with 3.5mm diameter, aligned to the fovea to Bruch’s membrane opening axis, and including 768 A-scans averaged 100 times, were used to measure RNFLT and RBV thickness and position (Figure 1). Additionally, we used infrared images to identify which of the measured RBV corresponded to the four major vessels (superior temporal vein – STV, superior temporal artery – STA, inferior temporal vein – ITV, and inferior temporal artery – ITA) and compared their positions between right and left eyes. The R-L asymmetry of RNFLT and RBV thickness was computed for each scan (Figure 2). A linear model was used to estimate the association between RNFLT and RBV asymmetries.

Results : We included both eyes of 219 individuals whose mean (SD) age was 50.9 (17.8) years. The mean number of RBV measured per eye was 15.0 (2.2). The mean RBV thickness was 7.1 (2.3) pixels. STV and STA were more superior in left eyes than in right eyes, by 2.3° and 3.6° respectively (P < 0.01). ITV and ITA positions were not statistically different between right and left eyes. There was no clear trend of R-L asymmetry in RBV thickness (Figure 2C). RNFLT was thicker in right eyes in the temporal superior sector and thicker in left eyes in the superior and superior-nasal sector (Figure 2F). The RBV thickness asymmetry was only weakly associated with RNFLT asymmetry (R² = 0.12).

Conclusions : There is little R-L asymmetry in RBV position and it only accounts for a small portion of the RNFLT asymmetry. This study suggests that R-L RNFLT asymmetry is due to anatomical configurations other than RBV position.

This is a 2020 ARVO Annual Meeting abstract.