Glaucoma is a slowly progressive neurodegenerative disease of the optic nerve, thus glaucomatous optic disc damage is irreversible in nature. Recently studies reported that OCTA-derived microvasculature parameters are reversible after IOP lowering treatment.1-3 A recent study by Liu et al. is in line with previous studies that retinal perfusion improves after IOP lowering surgery. This study has a strength in that it had a relatively long-term follow-up period of 6 months.
Meanwhile, the clinical implication of this finding is still unclear. Liu et al. speculated that restoration of retinal perfusion may represent the recovery of injured but viable retinal ganglion cells (RGC). However, in this study, VF parameters that reflect the RGC function did not change after surgery. Given that there is controversy on the VF improvement after IOP lowering surgery, the notion that perfusion restoration leads to the functional recovery of RGC cannot be fully addressed by the current study. Further case-control studies with long-term follow-up to compare the VF change according to the recovery of retinal nerve fiber layer (RNFL) perfusion is needed.
The cause of perfusion recovery of RNFL after trabeculectomy is also intriguing. Liu et al. suggested that this was directly related to the IOP reduction, rather than to the optic nerve head (ONH) structural recovery. However, in this study, the degree of perfusion recovery was not associated with that of IOP reduction. On the other hand, a study by Shin et al.2 reported that there was a significant relationship between the retinal microvasculature improvement and the maximal reduction of lamina cribrosa (LC) depth. Similarly, Kim et al.3 showed that an increase of laminar vasculature after trabeculectomy was strongly associated with the reduction in the LC curvature than with the IOP reduction. The two studies implicate that perfusion recovery of RNFL after surgery is better represented by the vascular and structural changes of the LC rather than IOP itself.2,3 Future studies on the relationship of perfusion recovery with the IOP reduction and structural changes of the ONH are warranted.
In conclusion, this study provides a basis for future investigations on the pathogenic role of the perfusion recovery on the glaucoma progression and biomechanical change of the ONH after IOP lowering surgery.