VASCULAR DENSITY AND PERFUSION IN GLAUCOMA

 

Optical coherence tomography angiography (OCTA) is a fast, noninvasive imaging technique that offers quantitative and volumetric evaluations of both the structural and vascular features of the retina and optic nerve. The changes observed in OCTA correlate topographically with the functional alterations identified through visual field assessments and the structural modifications noted on OCT.

There have been a couple of studies to analyze the radial peripapillary capillary vessel density (RPC VD) in glaucoma.

Joseph et al. have studied the peripapillary and macular perfusion densities in 20 eyes of POAG patients, 20 of NTG, and 15 of NTG, and compared them with normal eyes by OCTA analysis.  

All POAG, PACG, and NTG patients showed a lesser peripapillary perfusion density (PD) compared to normal subjects in all quadrants, which was statistically significant (P < 0.002).

Also, all POAG, PACG, and NTG patients showed a lesser superficial perifoveal plexus PD compared to normal subjects in all zones, which was statistically significant (P < 0.004).

In NTG, the peripapillary PD of the superior quadrant showed the least PD (P < 0.001), and in PACG, the inferior, nasal, and temporal quadrants showed the least PD, which was statistically significant (P < 0.002).

The mean peripapillary flux index of the outer zone was lowest in the PACG group, which was statistically significant (P < 0.001).

All forms of glaucoma (POAG, PACG, and NTG) were associated with decreased blood supply to the ONH and the perifoveal zone.

Apart from the mechanical damage to the optic nerve head, PACG is associated with significant retinal microvascular impairment.

Significant microvascular impairment in the perifoveal area in NTG is characterized by decreased PD in the outer and full zones.

Ashour et al have shown that RPC VD is reduced in eyes with glaucomatous cupping, and not in those with physiological cupping or in normal eyes. The study included 98 eyes from 98 patients, divided into 3 groups. Group 1 included 30 eyes with primary open-angle glaucoma, group 2 included 28 normal eyes with physiological cupping (normal OCT and no evidence of glaucoma), and group 3 included 40 age-matched normal eyes (vertical cup/disc ratio ≤0.5).

The study found significantly lower RPC VD across all retinal quadrants, compared to the other groups (P<0.001) in Group 1. But no significant differences were found between Groups 2 and 3 (P=0.559). Therefore, OCTA can be used to differentiate between glaucomatous and physiological cupping.

REFERENCES:

Joseph, Rachel; Apoorva, N.; Nayak, Lakshmi D.. Comparison of vascular parameters in primary open-angle glaucoma, primary angle closure glaucoma, and normal tension glaucoma with healthy subjects using optical coherence tomography angiography. The Pan-American Journal of Ophthalmology 7(1):143, April 2025. | DOI: 10.4103/pajo.pajo_23_25

Ashour DM, Madkour NS, Ebeid WM, Mahmoud RA. Peripapillary Vascular Density Differentiates Glaucomatous Cupping From Physiological Cupping Using Optical Coherence Tomography Angiography. J Glaucoma. 2025 May 1;34(5):415-420. doi: 10.1097/IJG.0000000000002530. Epub 2024 Dec 16. PMID: 39670861.