In this work, researchers quantified the variation of significant retinal blood vessel (BV) position outside optic nerve head (ONH) among glaucoma patients. More specifically, they investigated quantitative relationships between BV position and glaucoma diagnostic parameters
Positional shifts of major retinal blood vessels (BVs) with glaucoma progression are relevant for two reasons. First, as major BVs are visible on fundus images regardless of glaucoma severity, possible systematic shifts in glaucoma progression could be used in clinical diagnosis.
Second, as significant temporal BV positions correlate with the peaks of retinal nerve fiber layer thickness, it has been proposed to use major temporal artery positions on a circle with the radius of 1.73mm around the ONH to adjust circumpapillary retinal nerve fiber layer thickness (cpRNFLT) norms for optical coherence tomography measurements.
Though, if major temporal artery positions would substantially shift with glaucoma progression, it would be essential to quantify the BV shifts and to explicitly consider them to use BV positions in eyes with severe glaucoma as anatomical markers for pre-disease cpRNFLT peaks.
Researchers studied the relationship between major retinal blood vessel (BV) positions and glaucoma parameters based on pairs of Cirrus optical coherence tomography scans and Humphrey visual fields of 445 eyes from 445 glaucoma patients in the cross-sectional study between 2011 and 2014.
A trained observer marked the significant superior and inferior temporal BV (artery and vein) positions on four concentric circles around the optic disc. Analysis of variance was performed to analyze the group differences of BV positions related to the factors of radius, BV type, myopia status and glaucoma stage.
Subsequent t-tests were implemented to further study the effect of glaucoma stage on BV positions. The radial variations of BV positions were correlated to mean deviation and circumpapillary retinal nerve fiber layer thickness (cpRNFLT).
The study found significant main effects of BV type, radius and myopia status for superior and inferior BV positions and of glaucoma stage for superior BV positions (all p≤0.006) with significant superior artery nasalization in advanced compared to mild glaucoma on the two smallest circles (subsequent t-tests, p<0.05).
In addition, MD (r = -0.10, p = 0.04) and cpRNFLT (r = -0.12, p = 0.02) were significantly correlated to the angle difference of superior arteries between the innermost and outermost circles. In conclusion, researchers demonstrated that peripapillary superior artery positions are significantly nasalized for advanced glaucoma.
There were certain limitations in the study firstly correlations between superior artery nasalization and glaucoma diagnostic parameters were quite weak due to the confounding factors of large variance of individual BV anatomy.
Second, researchers didn't have longitudinal data in the study to evaluate the relationship between BV nasalization and functional progression rate. Future studies are needed to investigate a possible link between BV nasalization and visual field loss patterns.