TL;DR: Fixed dilated pupils in a cat are a critical veterinary emergency that may indicate serious neurological trauma or systemic disease. Seek immediate emergency care to prevent permanent vision loss or life-threatening complications.
What is mydriasis and why are my cat's pupils fixed and dilated?
When a cat's pupils remain wide and open regardless of how much light is in the room, it is a condition called fixed mydriasis. In a healthy eye, the iris should constrict the pupil in bright light to protect the sensitive retina. If the pupils are fixed and non-reactive, it suggests a significant breakdown in the neurological or physical pathways between the eye and the brain.
Is my cat having a veterinary emergency if their pupils are fixed and dilated?
- Urgency Level: High. Yes, this is considered a veterinary emergency.
- Fixed pupils can indicate life-threatening or sight-threatening conditions such as severe head trauma, acute high blood pressure (hypertension), retinal detachment, toxicity, or neurological disease.
- You should contact your veterinarian or an emergency animal hospital immediately, as early intervention is critical to preventing permanent damage or loss of life.
How does taking a photo of my cat's eyes help the veterinary team?
- Capturing a quick, clear photo or video of your cat’s eyes provides a vital triage tool for the clinical team.
- Clinical signs can change during transport due to adrenaline or shifting light conditions, making the original state harder to diagnose.
- A visual record allows the veterinary team to assess the severity of the neurological deficit more accurately the moment you walk through the door.
Clinical Context (Merck Veterinary Manual)
In cats presenting with acute blindness and dilated pupils, potential ophthalmic emergencies include sudden acute retinal degeneration syndrome (SARDS), optic neuritis, and retinal detachment. Intracranial disease and central blindness should also be considered if pupils are dilated and unresponsive to light. Etiologies range from systemic diseases (e.g., canine distemper, mycosis, granulomatous meningoencephalomyelitis), neoplasia, trauma, orbital cellulitis, systemic hypertension, intraocular myeloma, pituitary or paranasal masses, meningiomas, lymphosarcoma, cardiac arrest during anesthesia, seizures, to severe head trauma. A normal pupillary light reflex (PLR) may be present in cases of intracranial disease or central blindness.
Chapter: Ophthalmology, Emergency
Source: The Merck Veterinary Manual, 11th Edition (Page 1700)