Tear-deficient and evaporative dry eye syndromes of the horse.

Tear-deficient dry eye (keratoconjunctivitis sicca), and evaporative dry eye, with some overlap between these two categories, are two major categories of dry eye recognized in the horse. Careful examination of the eyelid margins, the inner and outer surfaces of the upper and lower eyelids, assessment of blink and third eyelid movement, specific testing of tear production, assessment of corneal sensitivity, and slit-lamp examination of the ocular surface before and after fluorescein dye application is recommended to detect dry eye problems. Rose Bengal dye application is also recommended in many cases. Facial nerve paresis is a possible complicating factor in some instances. Evaporative dry eye deserves closer scrutiny for it may be a contributory factor when ocular surface disease such as keratomycosis is present. Factors which influence ocular surface health need more close examination in horses.