Microvasculature dropout (MvD) area and angular circumference change rates are linked with circumpapillary retinal nerve fiber layer (cpRNFL) loss rates in eyes with primary open-angle glaucoma (POAG), according to research published in the American Journal of Ophthalmology.

The primary objective of this study was to determine whether MvD changes were associated with progressive cpRNFL thinning, and to establish whether these changes could signal glaucoma progression.

Researchers included a subset of 91 eyes of 68 patients (mean age 69 years, 50% women) from the Diagnostic Innovations in Glaucoma Study (DIGS) (Clinicaltrials.gov identifier: NCT00221897) in the analysis. The team performed 6 optical coherence tomography (OCT) and 6 optical coherence tomography angiography (OCT-A) imaging procedures over a mean 4 year period.


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Baseline analysis revealed 53 (58.2%) eyes with peripapillary MvD (21 inferior hemisphere, 4 superior hemisphere, 28 both). An additional 17 (18.6%) eyes without MvD at baseline developed it over the course of the study.

The researchers note that mean MvD area and MvD angular circumference nearly doubled from baseline to final follow-up visit (0.15 mm2 to 0.32 mm2 and 41.3° to 85.4°, respectively, P <.001 for both). They determined that mean rates of change were 0.05 mm2/year in MvD area and 13.22 degree/year in angular circumference. The rates of change were 0.02 mm2/year lower in eyes with a mean intraocular pressure (IOP) higher than 16 mmHg compared with those with lower mean IOP (P =.049).

After adjusting for confounders, the researchers found that the rate of MvD area change and baseline visual field mean deviation (VF MD) were associated with cpRNFL progression (-8.80 µm/year per 1 mm2/year increase; P =.008 and 0.06 dB/year per 1 dB worse; P <.001, respectively). They determined that MvD angular circumference rate of change (coefficient -0.30 μm/year per 10 degree/year; P =.009) and baseline VF MD (coefficient 0.05; P <.001) were the main factors associated with cpRNFL thinning.

In an univariable analysis, the team determined that MvD area change was linked with RNFL thinning in eyes with early glaucoma, but not in eyes with moderate to advanced glaucoma.

“With more than four years of follow-up, this study demonstrated that more than two-thirds of POAG eyes showed evidence of MvD throughout the follow-up,” according to the researchers. The team asserts that evidence of an association between faster cpRNFL thinning and more rapid increases in MvD area and circumference “may be useful for assessing progression in glaucomatous patients. These findings enhanced the current understanding of the role of MvD in glaucoma pathogenesis and may provide an additional strategy for monitoring glaucoma using OCT-A technology.”

Study limitations include the role of ocular magnification effects associated with axial length influencing OCT-A measurements of MvD area and the use of en-face images using the automatic demarcation of the Bruch’s membrane opening.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 

Reference

Micheletti E, Moghimi S, Nishida T, et al. Rates of choroidal microvasculature dropout and retinal nerve fiber layer changes in glaucoma. Am J Ophthalmol. Published online May 9, 2022. doi:10.1016/j.ajo.2022.04.024