The choroidal microvasculature of the parapapillary area as a biomarker of glaucoma development in the fellow eye of patients with unilateral glaucoma

Purpose To investigate the factors associated with the development of glaucoma in the healthy eyes of unilateral glaucoma patients. Materials and methods This was a retrospective observational case series study. All participants had unilateral primary open-angle glaucoma at the initial visit and were divided into two groups: one in which the fellow eyes developed glaucoma during the follow-up period and one in which the fellow eyes remained healthy. A complete ophthalmic examination, including best-corrected visual acuity testing, slit-lamp examination, intraocular pressure measurement, retinal nerve fiber layer and optic disk photographs, a 30-2 visual field test, and optical coherence tomography with angiography, was performed over a follow-up period of at least 3 years. Results A total of fifty-six patients were enrolled, and over the course of the study period, 11 patients developed glaucoma in the fellow eyes, while the fellow eyes of 45 patients remained healthy. At the baseline, the glaucomatous eye had a larger area of beta parapapillary atrophy, lower parapapillary choroidal vascular density (pCVD) within the area, and a lower prevalence of microvascular dropout than normal fellow eyes (P < 0.001, 0.013, 0.001, respectively). In the multivariate analysis, a reduced pCVD in the gamma parapapillary atrophy (gamma PPA) region was significantly associated with the development of glaucoma in normal eyes (odds ratio, 0.566; 95% CI, 0.342, 0.935; P = 0.026). Conclusions The pCVD within the gamma PPA region at baseline is the risk factor for the development of glaucoma in the normal fellow eye of patients with unilateral glaucoma.