A challenging case: Uveitis and secondary glaucoma in a cat - Veterinary Medicine
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A challenging case: Uveitis and secondary glaucoma in a cat
This cat's acute onset of hyphema and uveitis was initially attributed to trauma, but the ocular problems progressed despite treatment. These clinicians narrowed a long list of differential diagnoses to identify the cause.


VETERINARY MEDICINE


DIAGNOSIS

The results of aqueous humor PCR testing for bartonellosis were negative. The results of serum assays for antibodies against Toxoplasma species were IgG = 1:64 and IgM = 1:128. An IgM titer > 1:64 is consistent with recent exposure and active infection.9 Serum electrophoresis showed a normal distribution of the immunoglobulins. The mild elevation in serum globulins was likely due to antigenic stimulation or inflammation.

TREATMENT

Ten days later, the cat was presented to the ophthalmologist for a recheck examination. Progressive buphthalmos was noted in the right eye. Laser diode iridotomy was performed while the cat was anesthetized to control the IOP and for cosmetic reasons. Multiple holes were created at two-thirds the distance from the pupil to the base of the iris to deflate the iris bombé, allowing the iris to collapse away from the filtration angle,10 which enabled aqueous humor to flow out through the filtration angle and avoid worsening glaucoma.

The cat was treated for systemic toxoplasmosis with azithromycin (10 mg/kg orally once a day for seven days and then every other day for six weeks).11 An oral corticosteroid was also needed to control the arachidonic acid pathway and decrease permeability of the blood-ocular barrier to control uveitis and secondary glaucoma.12 Thus, an anti-inflammatory dose of prednisolone (0.5 mg/kg) was given orally once daily and was tapered over six weeks.

A topical nonsteroidal anti-inflammatory drug (NSAID), diclofenac 0.1% ophthalmic solution, was also administered initially four times a day and then twice a day in both eyes. A bacitracin-neomycin-polymyxin B ophthalmic ointment was administered four times a day to help prevent an infection in the ulcer in the right eye. The ulcer was likely a result of exposure keratitis secondary to buphthalmos. Avoiding infection is imperative because infected corneal ulcers can progress rapidly with stromal degeneration and corneal perforation, some in as little as 24 hours.13

The cat was discharged the same day that laser diode iridotomy was performed. Because the cat had clinical signs of toxoplasmosis two months earlier, it was highly unlikely that it was still shedding oocysts.14 The clients were advised that the best ways to avoid toxoplasmosis were to scoop cat feces daily before sporulation could occur and to avoid eating raw meat. It was also recommended that the cat not be allowed to hunt.14

FOLLOW-UP


3. The cat's left eye remains visual but the pupil is irregular in shape because of posterior synechiæ, where portions of the iris have attached to the anterior lens capsule.
IOPs were evaluated weekly, revealing a trend toward normal pressure. A month after referral to the ophthalmologist, the IOPs in both eyes were 14 mm Hg. The iris bombé had resolved in the right eye. However, the right eye remained nonvisual with a cloudy anterior chamber. The left pupil appeared irregular in shape because of focal regions of posterior synechiae, but it remained visual (Figure 3). The fundi were never able to be clearly visualized.

Six weeks after initiating the ophthalmologist's treatment protocol, the cat had improved, and all medications were discontinued except for the twice-daily diclofenac ophthalmic drops. Additionally, 40 mg of oral aspirin every third day was added after the prednisolone was tapered. The owners were instructed to monitor for gastrointestinal side effects while the NSAIDs were being administered; none were reported. The cat continues to improve and is eating well and has gained a half pound.

DISCUSSION

Uveitis is inflammation of the uveal tract (the iris, ciliary body, and choroid). The intraocular immune response is unique because the eye is an immunologically privileged site, which means the eye can modify intraocular antigen presentation and control the type and amount of inflammation.8 Immunocompetent lymphocytes migrate back to the eye as a result of activated inflammatory mediators. If the inciting antigen is not removed, chronic inflammation develops because of the immunocompetent lymphocytes in the uvea.2 Because of this pathophysiology, uveitis can result from systemic infection, autoimmune disease, neoplasia, or trauma.


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Source: VETERINARY MEDICINE,
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