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Hannah M Follett, Ching Tzu Yu, Owen Bowie, Chloe Guillaume, Dana Merriman, Phyllis Summerfelt, Joseph Carroll; Non-invasive assessment of retinal structure in the elderly 13-lined ground squirrel. Invest. Ophthalmol. Vis. Sci. 2022;63(7):4416 – F0095.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize retinal phenotypes in elderly thirteen-lined ground squirrel (13-LGS) eyes.
Eleven (2M, 9F) elderly 13-LGS (> 5 years old) were included. OCT imaging was used to assess anterior segment structure (22 eyes) and retinal morphology (20 eyes). NIR reflectance and SW-AF imaging were used to assess retinal and RPE health (22 eyes). Adaptive optics scanning light ophthalmoscopy (AOSLO) images were used to examine the cone mosaic (8 eyes). Retinal thickness and cone density measurements of elderly animals were compared to a control group of 1 year old animals (n=12 eyes, OCT; n=6 eyes, AOSLO).
NIR images showed abnormal expansion of the hyperreflective optic nerve head (ONH) signal, with a concomitant hypofluorescent signal on SW-AF images in 14 eyes. Hypofluorescent puncta were observed on SW-AF images in 10 eyes. Anterior segment OCT revealed lens opacifications in 19/22 eyes, obviating AOSLO imaging of 2 animals and precluding AOSLO analysis for 1 other animal. Posterior chamber OCT showed numerous abnormal phenotypes including hyperreflective vitreous laminations (20/20 eyes), hyperreflective inner retinal puncta (6/20 eyes), and a hyporeflective outer retinal cavity (1 eye). Disrupted outer retinal lamination adjacent to the optic nerve head (ONH) was observed in 17/20 eyes. Retinal and choroidal thickness values were within normative ranges for 5/20 eyes - the remaining 15 eyes had at least one retinal location with altered thickness of at least one layer, with 54% of the outliers being associated with disrupted retinal lamination within 5° of the ONH (Fig. 1). AOSLO images from 2 eyes showed a loss of discernable structure within 2.5° inferior of the ONH. The cone mosaic was otherwise normal, appearing contiguous with 91% of locations having density values within the normative range (Fig 2).
Elderly 13-LGS have abnormal lamination surrounding the optic nerve head and variable differences in retinal thickness when compared to young adult 13-LGS controls. In addition, the anterior segment findings can impose challenges with high quality imaging in all animals. It will be important to control for age in cross-sectional studies of 13-LGS retinal structure.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
Fig. 1 - Retinal thickness for elderly animals (circles) vs young controls (shaded region).
Fig. 2 - Cone density for elderly animals (circles) vs young controls (shaded region).
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