Macular and optic nerve head (ONH) vascular parameters can be measured with accurate reproducibility for longer than a year using optical coherence tomography angiography (OCT-A) technology, according to a British Journal of Ophthalmology report. The study provides evidence in favor of using OCT-A in addition to, but not to replace, OCT in the long-term follow-up of glaucoma. However, the research still shows stronger reproducibility using OCT-measured thicknesses. 

Investigators reviewed 88 eyes of 68 patients who were evaluated using OCT and OCT-A in at least 3 separate visits in a 1 to 1.5 year span. They used the imaging to measure a series of vascular and thickness parameters, including macular parafoveal vessel density (pfVD), ONH circumpapillary capillary density (cpCD), macular parafoveal ganglion cell complex (pfGCC), ONH circumpapillary retinal nerve fiber layer (cpRNFL), macula whole image vessel density (wiVD), ONH whole image capillary density (wiCD), macular whole image ganglion cell complex (wiGCC). 

Eyes were divided into 3 groups, healthy (n=15), glaucoma suspect (n=38), and non-progressing glaucomas (n=35). Researchers then applied a random effects analysis of variance model to estimate intraclass correlation (ICC) coefficients and estimate long-term variability. Participants were further divided into a macula cohort (which included 9 healthy eyes, 17 glaucoma suspects, and 17 eyes with glaucoma), and an ONH cohort (13 healthy eyes, 30 glaucoma suspects, and 30 glaucoma eyes). 


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Researchers report the ICC was lower for the OCT-A measurements than the OCT results, and that the long-term test-retest variability was between 2.29% and 2.39% for vascular parameters. “[S]erial measurements of OCT-A macula and ONH vascular parameters are not as high generally as the reproducibility of OCT parameters,” according to the study authors. However, the results also show that both “OCT- A measured macula and ONH vascular parameters have good long-term reproducibility, supporting the use of this instrument for longitudinal analysis.”

A significant number of poor scans and the fact that many patients were in early stages of glaucoma may have limited the study.  

The investigators also report that advanced patients’ age and lower signal strength index were both associated with decreasing long-term variability of vessel densities.

Reference

Nishida T, Moghimi S, Hou H, et al. Long-term reproducibility of optical coherence tomography angiography in healthy and stable glaucomatous eyes. Br J Ophthalmol. Published online December 21, 2021. doi:10.1136/bjophthalmol-2021-320034