CENTRAL BLINDNESS ASSOCIATED WITH A PITUITARY-ADENOMA IN A HORSE

A tentative initial diagnosis of total blindness of the right eye and incomplete vision loss of the left eye most likely due to retrobulbar optic nerve disease was made in a 21-year-old Thoroughbred mare. Postm ortem examination confirmed the presence of the pituitary-associated t umor. The lesion was well marginated, of uniform density and was consi stent with a pituitary adenoma. Pituitary pars intermedia adenomas hav e been reported to occur primarily in aged horses and are an infrequen t cause of vision deficits. The most common clinical signs associated with pituitary tumors in horses include polyuria, polydipsia, hirsutis m and failure to shed coat, swaybacked or potbellied appearance, hyper hidrosis, lethargy, dullness, weight loss, chronic infections, chronic laminitis, buccal ulcers, and estrus suppression and are generally th e result of pituitary-adrenocortical axis dysfunction. Diagnostic test ing should be aimed at evaluation of this axis.