Using OCT-angiography, investigators evaluated the time course of retinal vessel density reduction in relation to structural changes in patients with primary angle-closure disease.
Study design
This cross-sectional study included 77 control eyes, 65 primary angle closure glaucoma (PACG) eyes, and 31 primary angle closure (PAC) eyes with a history of high IOP.
OCT was used to evaluate the vessel densities of the optic nerve head (ONH), peripapillary, and macular regions, as well as structural measurements of the ONH rim area, peripapillary retinal nerve fiber layer (RNFL) thickness, and the macular ganglion cell complex (GCC) thickness.
Outcomes
As expected, vessel density and structural measurements were significantly lower in PACG eyes than in controls (all P<0.05). PAC eyes also displayed a thinner superotemporal RNFL compared with controls (127 μm vs 135 μm, P=0.01), but vessel densities were similar. This suggests that RNFL thinning secondary to high IOP spikes may occur before vessel density changes.
Additionally, an ad hoc analysis showed that OCT-A changes in vessel density may be helpful to follow progression in more advanced stages of glaucoma when the mean deviation on visual field is between −20 and −30 dB, presumably when the “floor effect" of the RNFL is in effect.
Limitations
Antiglaucoma medication could have confounded the OCT measurements by enhancing blood flow during OCT-A imaging. Several scans of poor quality also had to be excluded.
Clinical significance
Previously, we had to rely on visual field changes to monitor advanced glaucoma once traditional OCT could no longer show differences in RNFL measurements. This study highlights another way to monitor for subtle objective progression in the more advanced stages of disease.