In a dog with cataracts, pupillary light reflexes are typically:

• A. Normal
• B. Absent
• C. Diminished only in bright light
• D. Absent in the affected eye and present in the other eye

Answer: (A)

The pupillary light reflex is a subcortical reflex arc: light is detected by the retina, signals travel to the pretectal area and Edinger–Westphal nucleus, and the iris sphincter muscle constricts via the oculomotor nerve. Cataracts reduce the amount of light reaching the retina and blur vision, but they do not inherently disrupt the reflex pathway itself. As long as enough light gets through the lens to activate the retinal cells, the reflex can be elicited and both pupils will constrict normally. Therefore, in most dogs with cataracts, pupillary light reflexes are normal, even though the animal’s vision may be impaired.

In cases where the cataract is extremely dense and blocks light completely, the reflex in the affected eye may be diminished or absent, while the opposite eye can still show a normal consensual response. However, that is not the typical scenario—hence normal PLR is the best answer.