A one year old moggy male cat was presented in the Teaching Veterinary Clinical Complex, College of Veterinary Sciences and Animal Husbandry, Central Agricultural University, Mizoram, India with a history of anorexia since last three days with aimless movement. On clinical examination the right eye of the cat was found to be cloudy and blind with complete dilatation of pupil. The case was diagnosed as glaucoma in the right eye. The cat was treated with mannitol, carbonic anhydrase inhibitor, β-blockers and corticosteroid. The glaucoma recovered uneventfully within ten days.
Glaucoma is typically associated with elevated intraocular pressure (IOP) resulting from impaired aqueous humor outflow and leads to irreversible damage to the optic nerve and retina (Dubielzig et al., 2010). Primary glaucoma is relatively common and has strong breed predilections in dogs but is rarely diagnosed in cats. Secondary glaucoma is as frequent as primary glaucoma and constitutes 95% to 98% of glaucoma cases in cats (Gillian and Leandro, 2015). They are usually secondary to an ocular or systemic disorder that impairs aqueous humor outflow (uveitis, neoplasia, lens luxation, trauma). Glaucoma most often affects middle-aged to older cats (Gillian and Leandro, 2015), although it can occur in kittens. Congenital glaucoma is very rare (Sole et al., 2007). In the present case study the glaucoma is secondary in origin and is due to trauma.
A one year old moggy male cat was presented in the Teaching Veterinary Clinical Complex, College of Veterinary Sciences and Animal husbandry, Central Agricultural University, Aizawl, Mizoram, India with a history of not taking any food since last three days with aimless movement.
In clinical examination there was watery discharge, progressive uveitis in both eyes (Figure 1A). The right eye became enlarged with complete dilatation of pupil, cloudiness and blindness which was confirmed by putting hand in front of the eye. The left pupil was irregular shaped. Other clinical parameters such as temperature (101.1º F), respiration (20 beats/ min) and pulse (90/ min) were within the normal range. Further the case was diagnosed as glaucoma in the right eye.
The case was treated with Mannitol @ 1g/kg body weight intravenously for 3days, Triamcinolone acetonide @ 0.25 mg/kg body weight subcutaneously as a single dose, Prednisolone @1 mg/kg body weight orally once a day and Dorzolamide @ one drop in each eye twice a day for two weeks.
Results and Discussion
Eyes with glaucoma require frequent monitoring and adjustment of medications. Over time, affected eyes may become less responsive to topical medications. Changes in medications or an enucleation may be needed, especially if the eye is blind and becoming larger (Lellan and Miller, 2011). However the present case was controlled after seven days with medications and completely recovered after 10 days. The goals of the above therapy are to lower the pressure, save or maintain vision. Treatment of secondary glaucoma involves administration of anti-glaucoma drugs and therapy for the underlying cause. Carbonic anhydrase, an enzyme present in the ciliary body epithelium, contributes to aqueous humor production. Carbonic anhydrase inhibitors (CAIs) can decrease aqueous humor production in cats by over 40% (Sole et al., 2007). Dorzolamide 2% effectively lowers IOP when administered it might be considered a safe first-line drug of choice for dogs and cats with glaucoma, regardless of cause (Rachida et al., 2012). The β-blockers decrease IOP by reducing blood flow to the ciliary body, thereby decreasing aqueous humor production (Lellan and Miller, 2011). β- blockers have limited use as a single agent since they only modestly lower IOP in glaucomatous cats. While the β-blocker, timolol, may have significant additive effects when combined with CAIs in cats (Wang et al., 1999).
In glaucoma case the mannitol is an important systemic agent for decreasing IOP in severe and refractory glaucoma and should be used in emergency cases only. Mannitol increases the osmotic concentration of blood per fusing the eye, causing a marked reduction in aqueous humor productionand vitreous volume (Stadtbaumer et al., 2006). Vitreal “dehydration” directly decreases IOP and allows the intact lens to move posteriorly, increasing outflow of aqueous humor and reducing papillary block. Topical corticosteroid therapy is generally considered to be indicated for the management of chronic lympho plasmacytic uveitis in cats (Maslanka, 2014). However, steroid induced ocular hypertension is an important consideration both in the management of glaucomatous cats that have evidence of ocular inflammation, and in the monitoring of cats with chronic uveitis that may receive long term topical corticosteroid therapy (Lellan and Miller, 2011). As is the case in a subset of the human population, normal cats treated with either topical dexamethasone or 1% prednisolone exhibit a significant increase in IOP after about 2- 3weeks of treatment two or three times daily.
Glaucoma does not always respond to medications; the medications must be administered pain stakingly. Prognosis for secondary glaucoma varies, depending on the cause. The present case was respond well to medications, and the cat was recovered within ten days of post treatment.