Abstract
Purpose :
Many blinding diseases and aging impact specific geographic regions of the human retina, including the macula, the area responsible for our high-acuity color vision. Significant gaps in our knowledge about human vision exist due to technical barriers for studying phototransduction and light signal transmission specifically in the human macula. We aimed to establish criteria and methods for generating functionally viable peripheral and central human retina patches obtained from donor human eyes using ex vivo Electroretinography (ERG).
Methods :
Eye bank autopsy eyes were recovered within 2-5 hours of death; organ donor eyes within 45 min - 2 hours following cardiac death (DCD), or 1 – 20 mins following circulatory arrest in brain dead donors (DBD), and within 5 mins of death from macaques. Eyes were transported to the laboratory in oxygenated Ames medium. Retinal punches were taken from the macula and periphery and perfused with Ames media at 35-37oC in a custom ex vivo ERG device to measure light-induced electrical responses.
Results :
We recorded ex vivo ERG a-waves from macular samples in autopsy eyes and in DCD eyes up to 5 hours postmortem. Photoresponse amplitudes in the DCD maculae were not different from those recorded from freshly dissected macaque maculae (p=0.61, n=3/5 human and macaque biological/technical replicates) but declined with increasing enucleation delay (decay time constant = 74 mins). ERG b-waves were not normally present in these donors (n=20), with one exception, where we could record ERG b-waves in the peripheral samples from a research donor who died of stroke (>2 hours enucleation delay). Using DBD eyes, we were able to consistently revive ERG b-waves when enucleation delay was under 20 mins (n=5/10 biological/technical replicates). DL-AP4, known to block mGluR signaling from photoreceptors to ON bipolar cells, abolished the b-wave both in peripheral and macular samples.
Conclusions :
We established a method and distinct criteria for revival of ERG a- and b-waves in the human retina. We recorded the first ex vivo light responses from the human macula and used pharmacology to demonstrate that ERG b-wave in the human periphery and macula is mediated by photoreceptor-ON bipolar cell transmission. This approach enables future studies to advance our understanding of human vision, vision disorders and visual rehabilitation.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.