Longitudinal Evaluation of Chromatic Pupillometry and Retinal Thickness in Dogs With Sudden Acquired Retinal Degeneration Syndrome.

OBJECTIVE

To determine longitudinal changes in chromatic pupillary light reflexes (cPLR) and retinal layers in dogs with sudden acquired retinal degeneration syndrome (SARDS).

ANIMALS STUDIED: Clinical evaluation: Fifteen SARDS-affected and nine control dogs.

HISTOLOGY: Achieved globes from five SARDS-affected (1-7 years post-diagnosis) and eight age-matched controls.

PROCEDURES: Dogs underwent ophthalmic examination and electroretinography to confirm SARDS. Chromatic pupillometry and Fourier-domain optical coherence tomography (FD-OCT) were performed at baseline (once for control; < 1-month post-blindness for SARDS-affected dogs), and follow-up (3, 6 and 12 months post-diagnosis). The extent, velocity and latency of pupil constriction were evaluated. Retinal thickness was measured from the FD-OCT images. Ganglion cell counts were determined from histologic sections stained with hematoxylin and eosin.

RESULTS

At baseline, SARDS-affected dogs showed significantly reduced extent and velocity of red light PLR, and reduced extent with prolonged latency of white light PLR, relative to controls; white light velocity and all blue light parameters did not differ. White light PLR velocity significantly decreased over time in SARDS-affected dogs. FD-OCT in SARDS-affected dogs revealed progressive total retinal thinning but stable inner retinal thickness. Histology of SARDS-affected eyes identified diffuse outer retinal atrophy with relative inner retinal preservation; ganglion cell counts were not different between groups.

CONCLUSIONS

Chromatic pupillometry reflects the selective preservation of melanopsin-containing retinal ganglion cell function despite progressive photoreceptor degeneration in SARDS. The combined longitudinal use of chromatic pupillometry and FD-OCT provides a comprehensive assessment of the evolving functional and structural changes in SARDS-affected dogs.