This little cat was presented to me today having come out of a bush yesterday with its two pupils different sizes. What might be the cause of this and how might we verify our diagnosis?
This anisocoria is probably caused by some mild uveitis associated with trauma. Tonometry would be a useful tool to investigate this, as uveitis leads to a lower intraocular pressure, probably because released prostaglandins open up the unconventional outflow pathway for increased aqueous drainage from the eye, thus causing mild hypotony. The intraocular pressure was indeed lower, being 11mmHg compared with 16mmHg in the normal right eye. We used a mydriatic to ensure that no synechiae formation occured and left the eye to sort out the inflammation on its own, given that it was mild – we could have prescribed some topical steroid drops as well I guess.