Intraocular pressure, ocular perfusion pressure, retinal perfusion and electrophysiology in brain-dead organ donors

Abstract

Purpose : The relationship between intraocular pressure (IOP), ocular perfusion pressure (OPP), retinal perfusion and retinal electrophysiologic responses have been explored previously only in animal models. These studies have demonstrated that elevated IOP reduces OPP and when this exceeds the autoregulatory capacity of the retina vasculature, retinal perfusion and electrophysiologic responses are reduced. This study aimed to evaluate these interactions for the first time in the living human eye.

Methods : Three research-consented brain-dead organ donors, designated AOC039, AOC040, and AOC041, underwent ocular examination with biometry, fundoscopy, optical coherence tomography angiograph (OCTA; Spectralis, Heidelberg Engineering), and electroretinography (ERG, Diagnosys LLC). Prior to organ procurement, the anterior chamber was cannulated and IOP was directly measured and stepwise elevated at 10, 30 and 50 mmHg. Both eyes were evaluated in two donors (AOC040 and AOC041), and only the right eye in AOC039 due to time constraints. Systemic blood pressure was monitored continuously during testing by their life-support equipment. Photopic ERG and photopic negative response and OCTA-based perfused retinal capillary density were evaluated as OPP was reduced.

Results : Reductions in retinal capillary density and inner retinal function defined by OCTA and photopic ERG were observed in three human brain-dead donors associated with elevation in IOP and concomitant reduction in OPP (Table 1). Reductions in a-wave, b-wave, and PhNR amplitudes and latencies appeared to be correlated to OPP. There were more appreciable changes in perfusion and functional responses in eyes with lower systemic blood pressure (Figure 1).

Conclusions : In the living human eye, retinal perfusion and inner retinal function is acutely impacted by elevation of IOP, and this impact appears related to systemic BP and OPP. This novel approach will provide a viable model to study the autoregulatory responses to IOP elevation in the living human eye.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.