Diagnostic Accuracy and Relationship Between Optical Coherence Tomography Angiography Vessel Density and Structural/Functional Parameters in Healthy, Preperimetric, and Manifest Glaucoma Eyes.

Purpose: To evaluate circumpapillary vessel density (cpVD) in normal subjects, preperimetric glaucoma, and manifest glaucoma, assess the relationship between cpVD and both structural and functional parameters and compare the diagnostic accuracy of the structural and vascular measurements. Methods: An analytical cross-sectional study of 153 eyes of 83 individuals divided into three groups: Normal subjects, preperimetric glaucoma, and manifest glaucoma. All individuals underwent standard automated perimetry, spectral-domain optical coherence tomography (SD-OCT), and OCT angiography (OCT-A) centered on the optic nerve. We assessed structural (ganglion cell complex [GCC]/retinal nerve fiber layer [RNFL]) and functional parameters (mean deviation [MD]/loss variance [LV]). Results: Thirty-three normal subjects (66 eyes), 18 patients (30 eyes) with preperimetric glaucoma, and 32 patients (57 eyes) with manifest primary open-angle glaucoma were enrolled. The comparative study of cpVD showed a significant difference comparing glaucomatous subjects versus preperimetric glaucoma (P = 0.025) groups and normal subjects (P < 0.001). The cpVD was strongly correlated with functional parameters, MD, and LV (P < 0.001). Furthermore, cpVD was better correlated with RNFL (P < 0.001) than GCC (P < 0.001). Best regression was observed with mean RNFL (R2 = 0.752). The cpVD has a higher diagnostic value than RNFL and GCC, only between preperimetric and manifest glaucoma. Conclusions: Circumpapillary vessel damages seem to be less prominent, as it was seen only for the manifest glaucoma group. Microvascular changes appear to occur secondary to RNFL and GCC damages. They seem to be well correlated with visual function. Therefore, OCT-A is not as sensitive as SD-OCT in detecting early structural alterations.