Interocular symmetry of foveal avascular zone area in healthy eyes: an examination using swept-source optical coherence tomography angiography

Abstract

Purpose : One challenge in evaluating the influence of retinal vascular disease on foveal avascular zone (FAZ) area is that a standard procedure for determining a control value for FAZ area has not been established. Because individual differences in FAZ area are large (Fujiwara PLoS ONE 2017), the FAZ area of the healthy eyes of others is not appropriate for use as a control. One solution is to consider the FAZ area of the fellow eye as a control, particularly in the case of unilateral retinal vascular disease. However, the presence or absence of left/right differences in FAZ area of healthy fellow eyes is unknown. Therefore, we prospectively studied the FAZ area of healthy eyes using optical coherence tomography angiography (OCTA) and examined the presence or absence of left/right differences in fellow eyes.

Methods : We examined 236 eyes of 118 consecutive healthy subjects (70 females and 48 males, mean age, 39.1±18.9 years). The inclusion criteria for the eyes were a best corrected visual acuity of 20/20 or better and no history of ocular diseases. We captured OCTA images using swept-source OCT (DRI OCT-1, Topcon) and measured the FAZ area of the superficial capillary plexus using EnView software (Topcon). We analyzed the agreement of symmetry in the FAZ area of both eyes by paired t-test, Pearson's correlation coefficient, and Bland-Altman plots. We also measured axial length (AX), central retinal thickness (CRT), and retinal vascular density (RVD), and we performed multivariate regression analysis to investigate the relationships between the absolute interocular difference of FAZ area and these factors.

Results : There was no significant difference in the FAZ area between right and left eyes (0.32 ± 0.11 mm², 0.31 ± 0.11 mm², respectively, P = 0.608), and the right and left eyes were significantly and positively correlated with each other (P < 0.001, R² = 0.884). Bland-Altman plots showed that the mean interocular difference of the FAZ area was 0.03 mm² (95 % confidence interval, - 0.02 – 0.08 mm²). Multivariate regression analysis showed that age was significantly associated with the absolute interocular difference of FAZ area (P < 0.01, R² = 0.138).

Conclusions : There was no interocular left/right difference in FAZ area in healthy eyes.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.