Thank you. To confound things further, it's possible for a glaucomatous eye to also suffer from uveitis. A specialist veterinary ophthalmologist (please see here: www.acvo.org) should be considered when initial testing isn't confirmatory. Playing devil's advocate, I must tell you that middle ear inflammation (causing a Horner's syndrome) will cause a miotic (smaller than normal) pupil - not a mydriatic one (larger than normal). I'm going to post my synopsis of anisocoria (unequal pupil size) for you. There are quite a few considerations - some serious, some innocuous...
The two most common causes of anisocoria are the feline leukemia virus (FeLV) and the spastic pupil syndrome - a condition unique to cats in which owners report anisocoria which may sometimes be transient and independent of ambient light levels. Clinically, cats with this syndrome appear to be healthy, are visual, and have no ocular abnormalities beside unusual behavior of the pupils. Unfortunately, most affected cats test positive for FeLV at the initial presentation but not all which confounds the diagnosis.
Anisocoria also results from primary iridal (iris) disease (uveitis)- any inflammatory process causing miosis (an abnormally small pupil); and primary neurologic disorders involving cranial nerve III and Horner's syndrome (as mentioned above in association with middle ear inflammation).
The initial database should involve testing for FeLV and a complete ophthalmic examination including menace response, dazzle, palpebral, pupillary light, and vestibulo-ocular reflexes. Fluoroscein staining of the cornea should be performed looking for corneal trauma and intraocular pressure should be measured (the elevated pressure of glaucoma will enlarge the pupil (mydriasis) and the lowered pressures of uveitis will make the pupil miotic).
Much of the above is beyond the capability of many generalist vets so his vet may recommend referral to a board certified veterinary ophthalmologist. Please see here: www.acvo.org
Please respond with further questions or concerns if you wish.