Abstract
Purpose :
Manually applied focal laser lesions is a standard model for outer retinal layer degeneration but it often lacks consistency. We have developed MURIN (MUltimodal Retinal Imaging and Navigated-laser-delivery), an automated method for spatial control of laser exposure that incorporates the programming of a patterned array of lesion deposition based on optical coherence tomography (OCT) volume projection reference image (OCT-C) of the retina taken just minutes before.
Methods :
MURIN optically combines a 780nm spectral domain OCT system with 2-channel emission scanning laser ophthalmoscopy (SLO) and a 538nm photocoagulation laser. A software package was developed to adjust laser parameters for intensity, pulse duration, number of pulses, and target lesioning locations using an OCT-C scan. Various parameters were tested to titrate the extent of retinal injury in adult Muller glia-tdTomato reporter mice (Rlbp1:CreER; Rosaai14) and microglia-GFP; Muller glia-tdTomato reporter mice (Cx3cr1GFP; Rlbp1:CreER; Rosaai14). OCT, SLO and histology was performed at baseline, day 1, 3 and 7 post-injury.
Results :
We determined that the delivery of a single 100 millisecond 50 milliwatt with a spot size of 200 micrometer diameter pulse is sufficient to generate a lesion that selectively damages the outer retina with limited loss of RPE and minimal choroidal damage. We also determined that we can greatly expand the zone of injury while avoiding major retinal vasculature and without causing further damage to the inner retina by placing multiple lesions onto the retina with our method of spatial mapping. Histology at day 7 post-injury confirmed outer retinal layer degeneration and gliotic response at the injury site without collateral effects in the peripheral retina. Interestingly, immediately after laser exposure, photoconversion of the tdTomato reporter and de novo autofluorescence emission from the outer segments were detected in the green channel at the injury site. The signal is gradually reversed but detectable by SLO up to experimental end at day 7 post-injury.
Conclusions :
MURIN permits generation of extended focal outer retinal layer degeneration using a patterned array of laser lesions based on OCT-C scans. It can be used as a reliable model to study cellular processes and interventions following spatially and temporally controlled RPE disruption and photoreceptor loss.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.