Retinal hemodynamic effects of sub-Tenon anesthesia

TL;DR

This study investigated whether sub-Tenon anesthesia affects retinal blood flow during cataract surgery, finding that observed changes were likely due to imaging artifacts rather than real effects.

Contribution

The study provides evidence that sub-Tenon anesthesia does not cause measurable retinal hemodynamic changes, countering prior speculation.

Findings

Observed decreases in retinal vessel and perfusion density were not statistically significant after excluding low-quality OCTA images.

No significant changes in blood pressure or intraocular pressure were found after sub-Tenon anesthesia.

The initial findings were likely due to OCTA image artifacts rather than true hemodynamic effects.

Abstract

Sub-Tenon anesthesia techniques are commonly employed in ophthalmology. However, there is speculation that these techniques may have hemodynamic effects on the eye, potentially affecting patients with impaired ocular perfusion. This study aims to evaluate the impact of sub-Tenon anesthesia during cataract surgery on retinal vessel density (VD) and perfusion density (PD) in eyes affected by diabetic maculopathy (DM) or retinal vein occlusion (RVO), using optical coherence tomography angiography (OCTA).

The study included 20 patients receiving sub-Tenon anesthesia with unpreserved mepivacaine 2% for unilateral cataract surgery: 10 with DM and 10 with RVO, analyzing a total of 40 eyes (20 treated and 20 untreated). Blood pressure, intraocular pressure (IOP), and retinal microvascular changes measured via OCTA (VD, PD) were documented before and shortly after sub-Tenon anesthesia. The contralateral eye, which did not receive anesthesia, served as a control.

A negative association between sub-Tenon anesthesia to VD and PD was observed, with a VD-change of −1.5 ± 2.8 mm/mm2 (p = 0.02) in the treated eye compared to 0.7 ± 3.4 mm/mm2 in the untreated eye (p = 0.36) and a PD-change of −3.7 ± 7.0% (p = 0.029) in the treated eye compared to 1.6 ± 8.2% in the untreated eye (p = 0.38), suggesting a potential hemodynamic effect of sub-Tenon anesthesia. However, the quality of OCTA images strongly influenced these findings. After excluding lower-quality images (signal strength index <6), no statistically significant difference was observed between the intervention and control eyes, indicating a false positive correlation due to image artifacts. In the overall population, no significant changes in blood pressure and intraocular pressure were observed before and after the injection.

This study did not prove retinal microvascular changes associated with sub-Tenon anesthesia. The observed VD and PD reductions were likely caused by OCTA image artifacts rather than true hemodynamic changes.

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