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CLINICAL APPROACH TO THE CANINE RED EYE | methazolamide (2–5 mg/kg Q 8–12 H), decrease aqueous humor formation in the ciliary body. If secondary glaucoma associated with uveitis, hyphema, or lens luxation is suspected, latanoprost should not be used due to its miotic effects, especially if the lens is in the anterior chamber.17 Combinations of medications to maintain lower IOP within the normal or acceptable range for dogs are often needed. • Topical CAIs, such as dorzolamide or brinzolamide, are recommended Q 8 H.26 • Topical beta-blockers, such as timolol maleate 0.5% or betaxolol 0.5% (Q 8–12 H) are insufficient to control IOP when used alone but have a mild additive effect in lowering IOP when used in conjunction with a topical CAI.27 • If needed, a prostaglandin analogue may be used Q 12 H to help normalize IOP.28 Oral CAIs, such as methazolamide (2–5 mg/kg Q 8–12 H) have been recommended to help maintain IOP.29 However, a recent study demonstrated that, in dogs with glaucoma, addition of an oral CAI did not improve reduction of IOP over the decrease achieved with a topical CAI (dorzolamide) alone.30 In addition, when compared to a topical CAI alone, combination therapy with a topical and oral CAI was no more likely to provide long-term control in dogs with primary or secondary glaucoma.30-32 Clinical Note: Referral should be considered early in the disease process, especially if IOP fails to respond to medical management. Glaucoma is ultimately a surgical disease. Medical therapy will typically become ineffective within a year. Surgical intervention may prolong vision but has a relatively poor long-term success rate. • Laser ablation of the ciliary body (cyclophotocoagulation) or anterior chamber shunts, such as gonioimplants, used alone or together, offer longer periods of IOP control than medical management alone.33 • Endoscopic laser cyclophotocoagulation provides a longer period of control when combined with a gonioimplant, medical therapy, and frequent examinations.34-36 • Enucleation or evisceration is a humane option in most cases of blindness since the goal of therapy—if the eye is blind—should be pain relief. Prevention Generally, primary glaucoma begins as a unilateral disease but, eventually, the other eye develops it as well. Treating the "second" eye with a prophylactic medication even if IOP is within the normal range is critical in order to delay onset of disease. • Topical dorzolamide; beta blockers, such as timolol or betaxolol; and demecarium bromide are common prophylactics.31,37 • When a topical CAI is applied prophylactically, glaucoma develops, on average, in 196 days.31 Published time to onset of glaucoma for demecarium bromide and betaxolol when used prophylactically is 31 months and 30.7 months, respectively.37 ANTERIOR UVEITIS Causes of Red Eye When anterior uveitis is present, redness of the eye is due to episcleral injection, with 360° deep corneal vascularization if the disease is chronic (Figure 4 and 11). Other causes of redness related to anterior uveitis include May/June 2013 Today's Veterinary Practice 17