Eversion of the membrana nictitans occurs in a number of large breeds of dogs including Great Danes, Weimaraners, German shepherds, akitas and springer spaniels. Inversion also occurs, but less frequently. These anomalies commonly appear early in the dog's life, usually without antecedant disease; thus suggesting a congenital predisposition. The central shaft of the T-shaped cartilage of the nictitating membrane becomes curled, giving the membrana a rolled appearance. The effect is more damaging cosmetically than physically. However, an increase in tearing and mucus secretion may be noted.