Effects of Indirect Pupillary Light Reflex Stimulation With Colored Light on Corneal Specular Microscopy Performance in Dogs.

Blue light for indirect PLR stimulation improves corneal specular microscopy success rates and efficiency in conscious dogs.

This prospective study evaluated the effects of indirect pupillary light reflex (PLR) stimulation using differently colored lights (white, red, and blue) on the efficiency of corneal specular microscopy in conscious dogs. Twenty client-owned dogs with healthy corneas (38 eyes) were enrolled. One eye underwent specular microscopy while the contralateral eye was exposed to one of three light colors in randomized order. Procedural duration was measured from tracking onset to imaging completion, with a 30-second time limit imposed for animal welfare. Blue light yielded the highest success rate within 30 seconds (97.4%), followed by white (93.4%) and red (88.2%) light. Linear mixed-model analysis confirmed that blue light was associated with the shortest procedural duration and greatest degree of miosis, while red light produced the weakest pupillary constriction and longest procedural times. Although pupil diameter and light condition were closely correlated, pupil diameter alone was not independently associated with procedural duration after adjusting for light condition, making it difficult to fully separate the contributions of miosis from other wavelength-dependent physiological or optical effects. The authors suggest that intrinsically photosensitive retinal ganglion cells, which are maximally sensitive to short-wavelength (blue) light, may contribute to the enhanced PLR response. Clinicians performing corneal specular microscopy in awake dogs may improve imaging efficiency and procedural success by using blue light for indirect contralateral PLR stimulation.

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