Horses without ocular disease maintain similar electroretinographic responses and peripapillary retinal thicknesses across age groups.

OBJECTIVE

To determine the impact of age on equine electroretinography (ERG) parameters and retinal thickness in horses with healthy eyes. We hypothesized that ERG b-wave amplitudes would be significantly lower in older horses and that total retinal thickness would not vary significantly with age.

METHODS

Horses with clinically normal eyes comprising 3 age groups (≤ 10, 11 to 20, and ≥ 21 years) underwent scotopic and photopic ERGs, high-resolution fundus photography, and spectral-domain optical coherence tomography. Electroretinography results were compared between age groups using mean implicit times and amplitudes of the a- and b-waves for scotopic (3.0 cd⋅s/m2 white) and photopic (3.0 cd⋅s/m2 white at 2 Hz; background, 30 cd/m2 white) tests obtained with the RETevet. Optical coherence tomography-derived total retinal thickness (TRT) of the nasal, dorsal, and temporal peripapillary regions was compared between age groups.

RESULTS

15 horses were included, with 5 horses in each age group. No statistically significant differences in ERG implicit times or amplitudes were observed between age groups. No significant differences in nasal, dorsal, or temporal peripapillary TRT were identified between age groups.

CONCLUSIONS

No significant differences in retinal function as measured by ERG nor peripapillary TRT as assessed by optical coherence tomography were identified in young relative to middle-aged and aged horses without ocular disease.

CLINICAL RELEVANCE: While individual variation can be expected, aged horses maintain similar ERG parameters and TRT to young horses. In the clinical setting, reduced retinal function detected on ERG and retinal thinning should be considered pathologic and unrelated to the normal aging process.