TL;DR: Persistent pupil dilation in cats is a high-priority veterinary emergency that can signal serious issues like hypertension, glaucoma, or head trauma. Seek immediate veterinary care to prevent permanent blindness or other life-threatening complications.
What does it mean if my cat's pupils stay dilated in bright light?
Normally, a cat's pupils should constrict into narrow slits when exposed to bright light. If your cat's pupils remain wide and circular regardless of the lighting, this is known as persistent mydriasis. This condition indicates that the eye's normal reflex—or the neurological pathway connecting the eye to the brain—is compromised. It is often a sign of an underlying medical problem rather than a simple eye irritation.
Is persistent pupil dilation in my cat a veterinary emergency?
- Urgency Level: High. Please contact your veterinarian or the nearest emergency animal hospital immediately.
- Potential Causes: Dilated pupils can be a clinical sign of systemic hypertension (high blood pressure), retinal detachment, glaucoma, head trauma, or toxicity.
- Risks: These conditions are often painful and can lead to permanent blindness or life-threatening complications if not treated within hours.
How can taking a photo of my cat's eyes help the veterinary triage team?
- If your cat is stable, take a clear photo or short video of their eyes in a bright room.
- A visual record allows the vet to assess the exact size and symmetry of the pupils, check for cloudiness, and look for involuntary eye movements.
- This information helps triage staff prioritize your cat's case and prepare the necessary diagnostic equipment before you arrive.
Clinical Context (Merck Veterinary Manual)
In cats, dilated pupils in bright light (with diminished or absent pupillary light reflexes) associated with acute blindness can indicate several ophthalmic and neurological emergencies. Retinal detachment caused by systemic hypertension or intraocular hemorrhage should be considered. Intracranial disease, such as pituitary masses, paranasal masses, meningiomas, and lymphosarcoma affecting the optic chiasm, can also manifest with these signs. Central blindness, resulting from cardiac arrest during anesthesia, seizures, or severe head trauma affecting the optic tracts or occipital cortex, is another potential cause.
Chapter: Neurology, Ophthalmology
Source: The Merck Veterinary Manual, 11th Edition (Page 1700)