Multicolor imaging changes with retinal depth and healthy aging

Abstract

Purpose : Multicolor imaging is a subset of hyperspectral imaging which has shown utility in Alzheimer’s and Parkinson’s disease. This study investigates whether multicolor imaging in influenced by retinal depth and also whether multicolor imaging alters with healthy aging in two strains of wild-type mice.

Methods : Wild-type B6C3H and Sv129B mice (n=11 to 18/group, gender-balanced) were imaged using the Heidelberg Spectralis OCT2 Multicolor module. B6C3H mice were assessed at ages corresponding from young to middle-aged adults (3, 5, 8 months old) and Sv129B mice at old and very old ages (15, 18 months old). A 30° area centred on the optic nerve head was imaged infrared (IR, 815nm) green (GR 518nm) and blue (BR, 486nm) wavelengths at the retinal nerve fibre layer surface and then every 2D for 20D to span the retina. Data were analysed in FIJI, and after masking major blood vessels and optic nerve head the mean reflectance returned. Data were expressed as a ratio of short over long wavelength reflectances (averageBR&GR/IR) and analysed using linear-mixed-models with post-hoc Benjamini, Krieger and Kekutieli analysis.

Results : In the B6C3H strain there was a significant retinal depth effect with the reflectance-ratio decreasing deeper into the retina (p<0.0001). Additionally with advancing age there was a decrease in reflectance ratio across the retinal depth spectrum (p<0.05). In the Sv129B strain an interaction effect was found between retinal depth and advancing age (p<0.0001). With advancing age in the Sv129B strain there was a decrease in reflectance more in the inner than the outer retina (p<0.05). An interaction effect (p<0.0001) was observed when the B6C3H and Sv129B data were combined, with B6C3H young to middle-age groups exhibiting a higher reflectance-ratio particularly in the inner retina than the Sv129B old and very old-age groups (p<0.05).

Conclusions : Multicolor imaging exhibits a repeatable pattern of decreasing short/long wavelength ratio from the inner to outer retina. With advancing age multicolor imaging demonstrates a decrease in reflectance-ratio which is a pattern observed across two wild-type mouse strains and spanning young, middle and older ages. By characterizing multicolor changes in normal healthy eyes paves the way for application of a clinically available multicolor device to proteinopathies such as Alzheimer's and Parkinson’s disease.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.