Abstract
Purpose :
Since vascular factors may be involved in the pathogenesis of glaucoma, the distribution and pattern of vascular dropout may reflect particular phenotypes. Previous optical coherence tomography angiography (OCTA) case reports have described a wedge-shaped vessel defect that projects from the optic nerve head (ONH) around the fovea in an arcuate manner, similar to retinal nerve fibre layer (RNFL) defects. This study investigates the prevalence and quantification of this vessel loss and its relationship to other parameters.
Methods :
Spectral domain OCT and OCTA images from 299 subjects with suspect, early or moderate primary open angle glaucoma were reviewed (age: 67.5±10.65 years; mean deviation (MD): +2.38 to -11.45DB, mean= -1.63). Good quality OCTA images from 545 eyes were exported to ImageJ for analysis and to identify defects. Area and vessel density within the defect were quantified at the superficial vascular complex (SVC) level. Focal RNFL thinning was determined as a wedge-shaped defect of multiple confluent points below the 95% confidence interval.
Results :
Vessel wedge defects were present in 10.8% of OCTA images (59/545 eyes; 68.9±10.31 years; MD: +2.11 to -11.45DB, mean= -3.27, p<0.001 compared to total cohort). Of these, 83% were located inferotemporally, including 6 eyes with both superior and inferior involvement. 47 wedge defects were able to be fully quantified due to location of the wedge relative to scanned area. Vessel density within the wedge defect averaged 16.45±6.08%, which was 81% of the global macular SVC density. Wedge area was on average 5.51±4.54 mm2, with a width of 0.36±0.16 mm at the ONH. In all eyes with wedge vessel loss, wedge-shaped RNFL thinning was identified in the corresponding region of the OCT scan. Those with vessel wedge defects also had, on average, 5µm thinner peripapillary RNFL when compared to the total cohort (p=0.001). However, analysis between global vascular and structural parameters showed only weak or no correlations.
Conclusions :
This study quantified wedge-shaped vessel loss in a cross section of glaucoma patients and showed that approximately 11% of subjects have defects, predominantly inferiorly, that correlate with RNFL loss. The association between localised vessel loss and RNFL loss suggests there may be a common physiological cause, yet the temporal relationship between these factors is still to be defined and should be explored in a future longitudinal study.
This is a 2021 ARVO Annual Meeting abstract.