Evaluation of Parapapillary Choroidal Microvasculature Dropout and Progressive Retinal Nerve Fiber Layer Thinning in Patients With Glaucoma

Importance Parapapillary choroidal microvasculature dropout (MvD) is considered one of pathophysiological manifestations of glaucomatous damage. Objective To evaluate the longitudinal change in the parapapillary choroidal MvD in patients with primary open-angle glaucoma (POAG), and to determine whether this change is associated with progressive retinal nerve fiber layer (RNFL) thinning. Design, Setting, and ParticipantsThis prospective observational case series was conducted at a tertiary referral center in Korea and included 68 patients with POAG who exhibited parapapillary choroidal MvD in en face optical coherence tomography (OCT) angiography (OCTA) images who were enrolled from the ongoing Investigating Glaucoma Progression Study from January 1, 2016, through July 31, 2018. The mean (SD) follow-up period was 2.5 (0.2) years and observers were masked to the clinical characteristics of the participants for measurements. The OCTA images were obtained twice at an interval of at least 2 years, during which the RNFL thickness was measured at least 4 times in serial OCT examinations. Microvasculature dropout was defined as a focal sectoral capillary dropout with no visible microvascular network identified in the choroidal layer. The MvD area was measured in the OCTA images obtained at the baseline and the final follow-up. The significance of changes in the MvD area was defined using the 95% Bland-Altman limits of agreement. The rate of RNFL thinning was determined by linear regression of the serial OCT RNFL thickness measurements. Main Outcomes and Measures The association between the change in the MvD area and the rate of RNFL thinning. Results Of 68 Korean participants, 37 (54.5%) were women, and the mean (SD) age was 54.3 (13.1) years. Among 68 eyes, 22 (32.4%) showed increases in the MvD area during the follow-up. Faster global RNFL thinning was associated with a larger baseline parapapillary atrophy beta-zone (beta = -0.55; 95% CI, -0.96 to -0.14; P = .01), disc hemorrhage detection during the follow-up period (beta = -0.75; 95% CI, -1.67 to -0.34; P = .001), and a larger increase in the MvD area (beta = -4.74; 95% CI, -7.72 to -1.75; P = .002). The MvD area was not associated with the rate of RNFL thinning at baseline or the final follow-up. Conclusions and Relevance Microvasculature dropout enlargement was associated with progressive RNFL thinning in POAG.