Diurnal change of retinal vessel density and mean ocular perfusion pressure in patients with open-angle glaucoma

Abstract

Purpose: To investigate, in primary open-angle glaucoma (POAG) and healthy subjects, the pattern and magnitude of diurnal variation in optical coherence tomography angiography (OCTA) retinal vessel density (RVD).

Design: Prospective, observational cross-sectional study.

Participants: A prospective study was conducted on 20POAG patients and 19 healthy subjects.

Methods: Peripapillary/macular RVD (using swept-source OCTA), intraocular pressure (IOP), and systemic blood pressure (BP) were measured five times a day (8 a.m., 11 a.m., 2 p.m.,5 p.m. and 8 p.m.). The magnitudes and patterns of diurnal changes in RVD, diastolic BP, and mean ocular-perfusion pressure (MOPP) were analyzed and compared between the POAG patients and the healthy subjects.

Main outcome measures: The patterns and magnitudes of diurnal RVD change in OCTA.

Results: Intra-visit repeatability (0.755-0.943) and inter-visit reproducibility (0.843-0.986) for the RVD measurements showed excellent reliability. In the POAG patients, the magnitude of diurnal change in peripapillary RVD (9.71±7.04%) and macular RVD (7.22±4.73%) were significantly greater than that in the healthy group (5.73±3.85%, P = 0.013 and 5.51±3.45%, P = 0.042, respectively). The magnitudes of diurnal variations of IOP and MOPP in the POAG group likewise were greater than those in the healthy group (P = 0.003 and 0.039). As for the patterns of diurnal RVD change, interestingly, at 8 p.m., the macular RVD of the healthy group increased to the highest level (44.12±2.95%) while that of the POAG group decreased to the lowest level (40.41±2.54%).

Conclusions: In POAG eyes, diurnal change of IOP, MOPP and RVD was significantly greater than in the healthy eyes. These findings suggest that diurnal RVD changes might reflect the hemodynamic variation of POAG.

Fig 1. Swept-source optical coherent tomography angiography (SS-OCTA) scan and of the peripapillary area and macula showing superficial vascular plexus.

Swept-source optical coherent tomography (SS-OCT) scan (4.5 x 4.5 mm) of the peripapillary area and macula showing superficial vascular plexus as entire en face region (top). The value of the retinal vessel density (RVD) was calculated based on the intensity of the OCTA image. The “Density Map” (bottom) is a color map generated according to the brightness averages of the OCTA images.

Fig 2. Patterns of diurnal variation of RVD and hemodynamic parameters in healthy subjects and POAG patients.

The average RVDs in the peripapillary (optic disc head, superior, inferior, temporal, nasal) and macular (fovea, superior, inferior, temporal, nasal) areas are shown at the top. SBP, DBP, IOP, and MOPP were recorded every 3 hours from 8 a.m. to 8 p.m. The RVD and hemodynamic variations in each group were analyzed by ANOVA, and the inter-group comparison was assessed by a linear mixed model.

Fig 3. Representative cases of diurnal variation of peripapillary retinal vessel density (pRVD) and macular retinal vessel density (mRVD).

(A) A 44-year-old woman enrolled among the healthy subjects demonstrated an average pRVD of 55.87% and an average mRVD of 42.07% at 8 a.m. At 2 p.m., MOPP was the lowest, 48.22mmHg, and pRVD, 55.79%, was slightly decreased compared with 8 a.m., but at 8 p.m., MOPP had increased again to 52.22mmHg,with elevated pRVD and mRVD of 56.37 and 42.02%, respectively.(B) A 46-year-oldwoman with POAG (VF MD, -19.72 dB) had a MOPP of 59.66mmHg, an average pRVD of 50.96%, and an average mRVD of 43.57%, all of which were the highest daily values. At 5 p.m., the pRVD and mRVD had decreased to 48.33 and 39.07%, respectively, accompanied by a MOPP of 53.30 mmHg. However, at 8 p.m., all had decreased further, to 45.66, 37.76, and 46.22% for MOPP, pRVD, and mRVD, respectively.