Impact of dexmedetomidine as an adjuvant to peribulbar anesthesia on the retinal vasculature in glaucoma patients: an optical coherence tomography angiography study

Objectives To assess Dexmedetomidine's effect as an adjuvant to peribulbar anesthesia on the retinal vasculature in patients with glaucoma undergoing cataract extraction surgery via optical coherence tomography angiography (OCT-A). Participants Thirty-nine glaucoma participants planned for phacoemulsification were allocated into two groups. A 10 ml mixture of peribulbar anesthesia was administered to group I. This anesthetic mixture consisted of 4.5 ml of lidocaine 2% mixed with 4.5 ml of bupivacaine 0.5%,1 ml of dexmedetomidine (50 mu g), and 150 IU hyaluronidase. Group II was administered a peribulbar anesthetic mixture consisting of 4.5 ml of lidocaine 2% combined with 4.5 ml of bupivacaine 0.5%,150 IU of hyaluronidase, and 1 ml of normal saline, totaling 10 ml. Optical coherence tomography angiography was used 10 mi before and 10 min after injection to scan optic disc total vessel density, foveal superficial deep capillary plexuses (DCP) density, radial peripapillary capillary network density, and total vessel density plus foveal avascular zone (FAZ) diameter. We also checked the intraocular pressure (IOP) before and 10 min after the anesthetic injection. Results After the administration of the peribulbar anesthetic, group II demonstrated a notably higher significance in the DCP fovea median percent change (-43.7%) compared with group I (-2%) (P<0.001). Additionally, group II experienced a considerably greater median percent change in DCP total density (-22.4%) postinjection compared to group I (-0.8%) (P value < 0.001). The postinjection median percent changes in foveal total vessel density and superficial vessel density were -16.2% and -56.8% in group II, and -1% and -2.4% in group I, respectively, with a P value less than 0.001. Moreover, following the injection, the median percentage change in the diameter of the foveal avascular zone was significantly higher in group II (-40.6%) than in group I (-2.3%) (P value < 0.001). Additionally, there was a noteworthy increase in the optic disc's total vessel density and the median percentage shift in radial peripapillary capillary network density in group II (-13.1 and -13.7%, respectively) compared with group I (-1.2 and -1%, respectively, P value < 0.001). IOP before and after injecting the anesthesia was insignificantly different between the studied groups (P =0.198 and 0.069, respectively). Conclusion The addition of dexmedetomidine to the peribulbar anesthesia demonstrates a protective effect on the retinal microvasculature against the ischemic impact of anesthetic drugs with no significant effect on the IOP. This effect holds significant implications for glaucoma patients.