With optical coherence tomography angiography (OCT-A) is becoming increasingly relevant, research has been able to provide clinicians quantitative data, such as vessel density,retinal nerve fiber layer (RNFL) thickness, and deviation mapping. These findings may lead to a more robust understanding of the pathogenesis for primary open angle glaucoma (POAG). While that has yet to be fully elucidated, a study published in the Journal of Glaucoma does shows that a history of disc hemorrhages and paracentral visual field defects can be independently associated with wedge defects on OCT-A, which in this study, were present in approximately 45% of primary open-angle glaucoma patients. 

Investigators conducted examinations of any wedge defects found using OCT-A to find correlations between this sign and structural factors. OCT-A imaging for a cohort of  278 eyes of 186 consecutive patients (mean age 62.0±15.3 years, 53.6% men) — all with mild (33.45%), moderate (29.5%), and severe (37.05%) POAG — took place at University of Southern California Roski Eye Institute between October 2016 and March 2020. 

In total, 45.3% showed wedge-shaped defects in 1 or both hemispheres, 39.2% had patchy, nonshape-specific defects only, and 15.5% experienced profound loss involving both hemispheres. Upon univariable analysis adjusted for intereye correlation, significant associations emerged between wedge-shaped loss and mean RNFL per 10 µm decrease (P <.0001), vertical cup-to-disc ratio for each 0.1 increase (P <.0001), history of disc hemorrhage (DH, P =.011), paracentral deficit in visual field (VF, P <.0001), and average mean deviation dB (P =.011).


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Regarding categorical variables, important associations were found between localized wedge pattern and increased ICD-10 and HPA-graded glaucoma stages, but no correlation based on race or ethnicity. Previous research demonstrates inconsistent findings for the relationship between RNFL wedge defects and glaucoma severity. In addition, the current study found no correlations between wedge and baseline untreated IOP. Individuals with different baseline IOP values may have developed glaucoma from either mechanical or vascular origin, the investigation added.

Participants with profound loss were not included in risk modeling. Using multivariable logistic regression, odds for patients with DH history to display wedge deficiency was increased by 3.19 times, and those with paracentral VF defect had 4.38 times the odds to have wedge. Further, the odds ratio to exhibit wedge for those with RNFL thinning rose by 1.71, or 71% per 10 µm decrease; and 1.27, or 27% with each increase of 0.1 vertical cup-to-disc ratio.

Investigators note that association of wedge with DH may point to a common underlying factor. Prior studies have suggested DH is produced by mechanical stretching, traction, or a phenotype of unstable blood flow which eventually leads to weaker vessel walls less able to handle changing IOP. Yet, DH intermittently occurs in normal eyes, implying a multi-faceted cause. Other studies indicate that associations of wedge with paracentral VF loss may also be related to vascular impacts prompting ischemia of optic nerve fibers. Of patients in the current analysis with both wedge and paracentral VF loss, 40.3% displayed inferior defects, 22.6% superior, and 37.1% in both hemispheres. It was unclear why there were more inferior occurrences.

Due to the cross-sectional design, wedge defect changes across time were not evaluated. This aspect and no exploration of vascular impacts from Flammer syndrome limited the investigation. Nonetheless, this study’s data adds to a body of knowledge on possible underlying pathologies in glaucoma.

Reference

LeTran VH, Burkemper B, O’Fee JR, et al. Wedge defects on optical coherence tomography angiography of the peripapillary retina in glaucoma: prevalence and associated clinical factors. J Glaucoma. 2022;31(4):242–249. doi:10.1097/IJG.0000000000001991