Today's Veterinary Practice

MAR-APR 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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PEER REVIEWED 38 ACUTE GLAUCOMA: A TRUE EMERGENCY THE BASICS OF GLAUCOMA ■ Glaucoma is an elevation of the intraocular pressure (IOP) with associated optic nerve and retinal damage. ■ Glaucoma in dogs is always due to a decreased drainage of aqueous humor (AH)— increased production does not occur. ■ AH is drained through 2 different pathways: Most AH exits the eye via the iridocorneal angle (ICA), or conventional pathway, which is a complex sieve- like structure formed by the junction of the peripheral iris and cornea. Approximately 15% of AH drains through the nonconventional, or uveoscleral outflow, pathway. This drainage pathway is the target of the most effective glaucoma drugs, the prostaglandin analogs. ■ The balance between AH formation and drainage determines the IOP. CLASSIFICATION OF GLAUCOMA Classification of glaucoma is important to enable proper diagnosis and therapy. Glaucoma should be classified according to the underlying cause of the decreased AH drainage and the duration of the glaucoma ( TABLE 1 ). 1–3 Cause of Glaucoma Primary Glaucoma Primary glaucoma in dogs ( FIGURE 1 ) is associated with an inherited malformation and malfunction in the ICA. Over time, the capacity for AH outflow is reduced and IOP increases. Primary glaucoma is strongly breed related, and some of the most commonly affected dog breeds are the beagle, basset hound, Boston terrier, cocker spaniel, and shar-pei. Other breeds that are commonly affected include the Siberian husky, Samoyed, Labrador retriever, and toy poodle. Mixed-breed dogs are also affected by primary glaucoma. PRONE BREEDS Primary glaucoma is strongly breed related, and some of the most commonly affected dog breeds are the beagle, basset hound, Boston terrier, cocker spaniel, and shar-pei. shutterstock.com/Sigma_S Acute Glaucoma: A True Emergency Shelby Reinstein, DVM, MS, DACVO Veterinary Specialty and Emergency Center Levittown, Pennsylvania OPHTHALMOLOGY

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