Protocol for assessment of the pupillary light reflex in dogs without chemical restraint: preliminary investigation

Objective To explore the use of a modified pupillometry technique in dogs without chemical restraint. Materials and Methods Following dark adaptation, pupillary light reflexes were assessed in six dogs with sudden acquired retinal degeneration syndrome, in the unaffected eye of eight dogs with unilateral primary glaucoma (“predisposed”), and in 11 healthy dogs. Responses to red, blue and white lights were recorded and relative pupil sizes subsequently determined based on video recordings of each test. Results Mean testing time was 2.3 minutes (range 1.8 to 3.1 minutes), excluding time for dark adaptation. Baseline pupil size in dogs with sudden acquired retinal degeneration syndrome was greater than in normal and predisposed eyes. Pupil constriction was reduced in predisposed compared to normal and sudden acquired retinal degeneration syndrome eyes when stimulated with high‐intensity blue light. Compared to normal eyes, those with sudden acquired retinal degeneration syndrome had reduced pupil constriction when stimulated with low‐ and high‐intensity red light, low‐intensity blue light and white light. Clinical Significance Quantitative measures of pupil function were obtained from healthy and diseased eyes without the need for chemical restraint. Further investigations are warranted to validate the technique and evaluate its use in the management of canine glaucoma.