Inherited congenital microcoria, also referred to as congenital miosis, is characterized by bilateral small pupils (diameter less than 2 mm) that result from an underdevelopment of the dilator pupillae muscle of the iris (Holth and Berner, 1923; Simpson and Parsons, 1989). Iris transillumination defects are a constant feature. The pupil dilates poorly or not at all in response to topically administered mydriatic drugs. The disorder is transmitted as an autosomal dominant trait with complete penetrance and is associated with goniodysgenesis and glaucoma (Tawara and Inomata, 1983; Mazzeo et al., 1986; Toulemont et al., 1995).