A recent study showed that glaucoma patients being treated with medical therapy for the first time experienced increased vessel density (VD) at the optic nerve head (ONH) and other sites involved in the disease’s pathogenesis. The understanding of changes in ocular microvasculature caused by IOP-lowering medications can eventually help guide treatment and improve outcomes for glaucoma patients. 

This study used OCT angiography (OCTA) to measure and quantify the ocular microvascular parameters. Researchers recruited 20 total participants from the glaucoma clinics of the Singapore National Eye Center for this study. They observed 36 total treatment-naive eyes, 26 of which began receiving a prostaglandin analog  once daily. The remaining 10 untreated eyes were used as controls. All study subjects were either diagnosed with primary open-angle glaucoma, ocular hypertension or primary angle closure disease. 

IOP decreased by 26.1% in eyes receiving treatment and 0.18% in the controls in three weeks or more following initiation of treatment. Reduction in IOP was found to be significantly correlated with an increase in ONH VD for eyes receiving treatment. Increases in VD at the radial peripapillary capillaries were also found to be correlated with IOP. However, there was no significant correlation between IOP and VD at the macula.

“It is unknown whether the modest improvement that we observed in some of the OCTA parameters occurred by reperfusion or possibly because of revascularization. Importantly, as baseline IOP was not correlated with baseline VD or flow area, it may suggest that the changes in OCTA parameters be ascribed to changes affected by IOP reduction,” the researchers noted in their paper.

One of the major limitations of this study is the small sample size and brevity of the follow-up period, which both hinder the generalizability of the findings. Study eyes were only observed twice; once at baseline and once after three or more weeks of latanoprost treatment. “More research is needed with longer follow-up to further reveal the intricate multifactorial influences of ocular perfusion in glaucoma and how this ultimately influences glaucoma progression in the long term.”

Liu C, Umapathi RM, Atalay E, et al. The effect of medical lowering of intraocular pressure on peripapillary and macular blood flow as measured by optical coherence tomography angiography in treatment-naive eyes. J Glaucoma. June 2021;30(6):465-472.