The pupil is large and more commonly occurs in young women. Tonic pupil, or Adie pupil, is a well-known cause of anisocoria.
TNP is an example of a large, abnormal pupil. Magnetic resonance angiogram (MRA) has a threshold of 3 to 5mm and may indicate other pathologies. Diagnosis is radiological with computed tomogram (CT) or magnetic resonance imaging (MRI). Patients usually experience pain with this entity. The most well-known, life-threatening cause of TNP is a posterior communicating artery aneurysm causing pressure on the third nerve. Isolated pupillary dilation is not classically considered a third nerve palsy however, careful evaluation for subtle ptosis or abnormal extraocular movement is necessary to eliminate a TNP using this criterion. "The vet explained that because of the way Smitty sleeps (with one eye open and one closed with his paw holding it shut), his pupils dilate differently."ĭo you have funny and adorable videos or pictures of your pet you want to share? Send them to with some details about your best friend and they could appear in our Pet of the Week lineup.Important etiologies of anisocoria include third nerve palsy, Adie pupil, pharmacologic mydriasis, pharmacologic miosis, traumatic mydriasis, physiologic anisocoria, and Horner syndrome.Ī third nerve palsy (TNP) may spare the pupil or cause it to dilate with no reaction to light or convergence. "We took Smitty to the vet five hours after the post on Reddit," she said. In this case, Cecile did take Smitty to be checked out quickly and luckily, the vet was not concerned. "If a cat owner sees that their cat's pupils are different sizes or shapes, particularly if it has occurred very suddenly, then they should contact their vet immediately," said Foreman. Without examining the specific cat, it is difficult to determine the cause of the pupil changes. Because of this, anisocoria can be a result of many disorders of the eye, head, and neck through their impact on this ocular pathway," said Foreman.
#Pupils two different sizes series#
Pupil size and shape is very finitely controlled by a long series of nerves-the sensory and motor pathway travels from the eye, down the neck, looping back up to the eye. "Anisocoria is not a normal phenomenon and is often a sign of an underlying problem in an animal. My cat had the same problem, it was caused by an infection." Is Anisocoria Dangerous in Cats? While another wrote: "Do take them to the vets to get it checked out. I'd recommend contacting your vet ASAP, and get advice from them," said one commenter. Reddit users online shared their reactions and advice. "There has been some sort of disruption in either the sensory or motor element of the nervous pathway in this cat which has led to this inequality in pupil size and shape," she explained.Īnother cat with a similar pupil issue was previously compared to David Bowie online due to his differently dilated pupils. In comparison, the left pupil is smaller and misshapen, a D-shape rather than a vertical slit."įoreman explained that both pupils should contract and dilate at the same time and rate in response to direct and indirect light.
This cat's right eye is what is considered normal to see when looking at a cat, a pupil that is vertically slit. Anna Foreman told Newsweek: "The cat in this picture has something called anisocoria-pupils of different sizes. Is this something serious?" Why Are My Cat's Pupils Different Sizes?Įverypaw Pet Insurance's in-house vet Dr. She snapped a picture and posted it online, asking: "Woke up to our kitty having two different sized pupils. "It suddenly appeared like that early in the morning, and later in the day, it corrected itself," explained the owner. One day, Smitty's owner was concerned about his eyes when she woke to find him with differently dilated pupils. His owner Cecile took to the internet to ask for advice when she noticed that her kitten's eyes looked a little odd. Eight-month-old Smitty worried his owner when he awoke with differently-sized pupils.
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