It has long been a debate whether vascular mechanism plays a role in the pathogenesis of glaucoma. As OCT angiography (OCTA) has facilitated the in-vivo assessment of the ocular perfusion, the interest in the compromise of the retinal vasculature in glaucoma has been boosted. A recent study by Lin TPH et al. adds to the literature that generalized microvascular attenuations were observed in normal-tension glaucoma (NTG) patients by using both fundus photography and OCTA. Moreover, OCTA-derived retinal capillary metrics attenuations were more strongly associated with NTG than fundus photography.
Degeneration of the retinal capillary vasculature is a potential surrogate marker of RGC axonal loss in glaucoma
These findings support the notion that compromised retinal perfusion may play a role in the pathogenic process of NTG. Also, this study highlights the clinical utility of OCTA in assessing retinal vasculature.
Meanwhile, it is still unclear whether vascular compromise is the result or cause of the glaucomatous damage. Theoretically, optic nerve head degeneration can be derived from reduced ocular perfusion.1 On the other hand, there is an increasing number of studies utilizing OCTA that support the hypothesis that reduced retinal perfusion is rather a consequence of retinal ganglion cell (RGC) degeneration.2,3 Given that an area of retinal capillary attenuation coincides with that of RNFL defect, microcirculatory insufficiency is rather a consequence of metabolic demand driven by the loss of RGC axon. If vascular compromise is a primary change, it should have followed the retinal arterial territory.2 Also, OCTAderived macula vessel density percent loss was significantly less than that for ganglion cell complex (GCC) thickness in early glaucoma eyes.3
Either way, degeneration of the retinal capillary vasculature is a potential surrogate marker of RGC axonal loss in glaucoma.
Further work is needed to elucidate the pathogenic role of the optic disc vascular perfusion on the pathogenesis of glaucomatous optic neuropathy.