Abstract
Purpose :
Inherited retinal disorders and dry age-related macular degeneration undergo the progressive dysfunction and death of photoreceptors at different rate and locations. However, isolated functional characterization of specific regions of the retina, as for example geographic atrophy lesions or therapeutically treated areas, is often challenged by the lack of spatial targetability, and collateral bleed-through responses of nearby cells. Further, different cell and gene therapy approaches may target discrete regions of the retina and photoreceptor types. Therefore, we developed optical coherence tomography (OCT) guided variable-spot electroretinogram (vsERG) platform to enable spatially resolved and isolated measurement of retina function with minimal response from unintended region(s).
Methods :
In the novel Nanoscope Instruments’ NS-NEEL OCT guided vsERG platform, the stimulation light path for ERG and OCT are combined such that the tunable lens can deliver stimulation spot sizes ranging from 30 μm to 4 mm. Also, the precise scanning optics enable unrestricted placement of the stimulation spot on the retina. ERG responses from normal and photoreceptor-lacking areas of the rat and pig retina were measured. Different stimulation spot sizes were used with pre-selected wavelengths (455, 530 and 630 nm) at various intensities to determine functional responses from rods and the different types of cones.
Results :
VsERG measurement showed reduced ERG response from regions lacking photoreceptors compared to normal retinal regions. Both, cone and rod response (detected with photopic and scotopic stimulation respectively), exhibited lower ERG-signals in the photoreceptor-degenerated retinal regions. In addition, vsERG recording from different types of cones produced unique characteristic responses based on stimulation wavelength (blue, green and red), which decreased concomitantly with decreased size of the stimulated retinal area.
Conclusions :
Our results demonstrate that OCT-guided vsERG with selected stimulation wavelengths is suitable for functional evaluation of different types of photoreceptors in normal and diseased retina in a highly defined region with minimal contribution from adjacent areas. OCT guided vsERG based monitoring of physiological function will enable improved characterization of retinal degenerative diseases and evaluation of therapeutic interventions.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.