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| CLINICAL APPROACH TO THE CANINE RED EYE » Applanation tonometry: Mean IOP ± standard deviation (SD) in the dog is reported as 17 ± 4 mm Hg15 » Rebound tonometry: Mean IOP ± SD in the dog is reported as 10.8 ± 3.1 mm Hg (range, 5–17 mm Hg)16 • A recent study has shown that inexperienced personnel can obtain comparable intraocular values in dogs using either applanation or rebound tonometry.17 Clinical Note: Minor variations in IOP are noted secondary to diurnal variations, corneal scarring and pigmentation, and stress related to the white coat effect.18-20 » » » » Corneal edema Mucopurulent discharge Signs of pain (blepharospasm and epiphora) Stromal loss, malacia, and WBC infiltration. Referral & Advanced Therapy It is prudent to refer all patients with deep stromal ulcers, descemetoceles, and ruptured eyes to an ophthalmologist for surgical evaluation in order to save the globe and vision. Surgical interventions include conjunctival flap, corneal graft, or corneal-conjunctival transposition.4,5 Recently, bioscaffold materials (ACell, acell.com) have shown promise for corneal ulcer treatment. These materials help promote healing of deep corneal ulcers and, when combined with a conjunctival flap, can be used for surgical repair of descemetoceles or penetrating corneal injuries.13 Another recent study has shown that the use of amniotic membranes can decrease scarring, promote healing of corneal injuries, and provide anti-inflammatory properties.14 GLAUCOMA Causes of Red Eye In a patient presenting with glaucoma, redness of the eye is due to episcleral injection, with deep corneal vessels that form a 360° perilimbal pattern if the condition is chronic. Clinical Note: Pain, corneal edema, and disturbance of vision may be present with glaucoma. Diagnosis The only diagnostic sign of glaucoma is increased intraocular pressure (IOP). • IOP is measured by applanation (Tono-Pen, reichert. com; I-pen Vet, imedpharma.com) or rebound (TonoVet, icaretonometer.com) tonometry. • Normal IOP in the dog varies between 10 to 20 mm Hg 16 Today's Veterinary Practice May/June 2013 Classification Primary glaucoma (Figure 10, page 15) in dogs is almost always unilateral and often associated with a narrow or closed filtration angle. • Once glaucoma becomes severe, episcleral injection is the predominate cause of redness. • Increased IOP typically results in slow pupillary light responses and mydriasis in the affected eye. • Buphthalmia (enlargement of the globe) occurs in patients with chronic glaucoma, but not in those with acute glaucoma or ocular hypertension. Secondary glaucoma is often seen with uveitis (Figure 11, page 15) or anterior lens luxation (Figure 3). Referral for gonioscopic examination or advanced imaging is required to classify type of glaucoma based on the iridocorneal angle morphology. While only the most superficial parts of the iridocorneal angle can be visualized with a goniolens, the entire ciliary cleft can be visualized with advanced imaging techniques, such as high-resolution ultrasonography or ultrasound biomicroscopy.21,22 Treatment Initial medical therapy for acute primary glaucoma is aimed at rapidly reducing IOP. • Ophthalmic solutions containing prostaglandin analogues, such as latanoprost 0.005% or travoprost 0.004% (if available), should be used to rapidly decrease IOP; latanoprost 0.005% is administered Q 1 to 2 H until IOP decreases.23 • Intravenous mannitol (1–2 g/kg, slowly administered over 15–20 min) is used as an alternative to topical prostaglandin analogues or in patients that do not respond to topical therapy within 2 hours. » Withhold water for 4 hours after administering mannitol.24 » Adverse effects may occur in dehydrated or systemically ill animals, especially those with cardiac or renal disease; therefore, patient monitoring is critical when administering any osmotic diuretic, such as mannitol. • Oral carbonic anhydrase inhibitors (CAIs), such as