Spheroidal degeneration of cornea and conjunctiva. 3. Incidences, classification, and etiology

Spheroidal degeneration, an extracellular protein deposit in the cornea and conjunctiva, has been found in three basic patterns in the southwestern portion of the United States: (1) the primary corneal form which is seen in the horizontal meridian adjacent to the limbus; (2) secondary corneal form found anywhere in the cornea and in geographic areas free of environmental extremes usually associated with significant corneal pathology; and (3) a conjunctival form which is frequently associated with pinguecula. One of the three forms of spheroidal degeneration was found in over 40% of patients over the age of 50 years, and was seen three times more frequently in males than females; also, the corneal forms were more frequently associated with glaucoma. Although many factors may be important in the etiology of this entity, normal aging changes and sun rays probably play a major role.