Irregular astigmatism induced by annular tinted contact lenses.

Three patients developed irregular corneal astigmatism while wearing annular tinted soft contact lenses on a daily basis for 1.5 to 3 years. There was severe keratometer mire distortion, and photokeratoscopy revealed central and midperipheral corneal topographical irregularities in four of six eyes. In a masked protocol, scanning electron microscopy of four contact lenses revealed physical deformations in three lenses worn on affected eyes. We propose that latent stress vectors were created when the affected contact lenses were tinted. With patient usage, the stress vectors matured into physical deformations that induced irregular astigmatism. The astigmatism resolved upon discontinuing wear of these lenses, and the patients were able to wear other lenses with no recurrence of symptoms.