Peripapillary Vessel Density In Unilateral Preperimetric Glaucoma

Purpose: To investigate vessel density (VD) of radial peripapillary capillaries (RPC) and structural alterations in patients with unilateral preperimetric glaucoma (PPG) using optical coherence tomography angiography (OCTA). Methods: This cross-sectional observational study included 13 untreated patients with unilateral PPG. PPG eyes had larger excavation and abnormal thinning of retinal nerve fiber layer (RNFL) and/or ganglion cell complex (GCC) compared with fellow eyes (F). Both RNFL and GCC thickness in F were statistically within normal limits and/or borderline. The RPC VD on optic disc (idVD), of peripapillary (ppVD) and whole image (wiVD) scan area was measured. Twenty healthy eyes (H) served as controls. Structural and vascular parameters obtained by spectral-domain OCT/OCTA (Optovue; Fremont, CA) were compared between PPG, F and H. Results: Mean RNFL and GCC average thickness in microns differed significantly (p<0.001) between PPG (82.4 +/- 7.1, 81.4 +/- 5.9), F (91.0 +/- 7.1, 88.5 +/- 3.8) and H (103.5 +/- 6.0, 99.3 +/- 5.7). PPG compared with F showed significantly (p<0.001) lower mean ppVD (43.8%+/- 3.0% versus 47.8%+/- 3.2%) and wiVD (45.9%+/- 3.5% versus 50.1%+/- 3.9%). Mean ppVD (49.7%+/- 2.4%) and wiVD (52.6%+/- 3.0%) in H were not significantly higher than in F. Mean idVD showed no significant differences among the 3 groups. Areas under the receiver operating characteristic curves (AUROCs) for RNFL, GCC, ppVD and wiVD between PPG and H were excellent (>0.9). AUROCs between F and H demonstrated an excellent diagnostic ability for structural parameters and a poor one (<0.7) for vascular parameters. Conclusion: Affected eyes of patients with unilateral PPG demonstrated significant RPC dropout. Clinically unaffected eyes showed thinner structural parameters but no significant microvasculature differences compared with non-glaucomatous eyes. Diagnostic ability of peripapillary vascular parameters was not superior to structural measurements. Microvascular dysfunction seems to be an early but not a primary event in glaucoma continuum at the stage of undetectable visual field loss. OCTA can be useful in early glaucoma diagnosis.