Enlargement of microvascular dropout toward the disc-fovea axis indicates new central visual field defect in glaucoma

We aimed to evaluate the relationship between the increase in choroidal microvascular dropout (MvD) toward the disc-fovea axis and the development of central visual field defect (CVFD) in patients with glaucoma. We retrospectively reviewed the longitudinal medical records of patients who underwent at least two optical coherence tomography angiographies (OCTA) with significant macular retinal ganglion cell (RGC) damage at baseline. Patients were divided into three groups: Group 1, no CVFD; Group 2, new CVFD during the follow-up period; and Group 3, CVFD at baseline. The angular extent of MvD and the change were investigated. We had 35 eyes in Group 1, 25 in Group 2, and 43 in Group 3 with OCTA over an average of 3.1 ± 1.3 years. At baseline, MvD was significantly more frequent and larger in Group 3 compared to Groups 1 and 2; there was no difference between Groups 1 and 2, aligning with the absence of baseline CVFD. The mean final MvD extent was significantly smaller in Group 1 (9.9°) than Groups 2 and 3 (43.6 and 44.8°, P < 0.001), also aligning with the presence of final CVFD. Quantitatively, Group 2 with developing CVFD exhibited significantly greater mean increase in MvD (17.8°) than Groups 1 and 3 (0.9 and 6.0°, P < 0.001). In contrast, the changes in OCT-based thicknesses did not differ among the three groups in the period. In conclusion, in patients with glaucoma who had significant RGC damage in the macular area, longitudinal increase in MvD coincided with development of new CVFD, both in terms of the presence and in terms of angular extent, in a three-year follow-up period.