Intraocular pressure increases the rate of macular vessel density loss in glaucoma

Background/aims To evaluate the relationship over time between intraocular pressure (IOP) and the rate of macula whole image vessel density (wiVD) loss and whole image ganglion cell complex (wiGCC) thinning in glaucoma Methods From 62 patients in the Diagnostic Innovations in Glaucoma Study, 59 Primary open-angle glaucoma and 27 glaucoma suspect eyes with mean follow-up of 3.2 years were followed. Optical coherence tomography angiography (OCT-A)-based vessel density and OCT-based structural thickness of the same 6×6 mm GCC scan slab were evaluated. Univariable and multivariable linear mixed models were performed for all eyes and also a subset of them in which peak IOP <18 mm Hg to investigate the effect of IOP parameters on the rate of wiVD and wiGCC change. Results The mean baseline visual field mean deviation (95% CI) was −3.3 dB (−4.4 to –2.1). Higher mean IOP (−0.07%/year per 1 mm Hg (−0.14 to –0.01), p=0.033), peak IOP (−0.07%/year per 1 mm Hg (−0.13 to –0.02), p=0.004) and IOP fluctuation (IOP SD) (−0.17%/year per 1 mm Hg (−0.32 to 0.02), p=0.026) were associated with faster macular vessel density loss. Faster wiGCC thinning was associated with higher mean IOP (−0.05 µm/year per 1 mm Hg (−0.10 to –0.01), p=0.015), peak IOP (−0.05 µm/year per 1 mm Hg (−0.08 to –0.02), p=0.003) and IOP fluctuation (−0.12 µm/year per 1 mm Hg (−0.22 to –0.01), p=0.032). In eyes with peak <18 mm Hg, faster wiVD progression was associated with higher mean IOP (p=0.042). Faster wiGCC progression was associated with higher mean IOP in these eyes (p=0.025). Conclusion IOP metrics were associated with faster rates of overall macular microvascular loss and also in the eyes with peak IOP <18 mm Hg. Future studies are needed to examine whether additional IOP lowering reduces the rate of microvascular loss in patients with glaucoma. Trial registration number NCT00221897.