title: Induced corneal astigmatism with hydrophilic contact lenses.
abstract: Changes in keratometer readings were measured in 87 patients, wearing hydrophilic contact lenses for three to more than eighteen months. Twenty-four eyes in the group had an increase of +0.75 or more in the keratometer readings, which invariably involved the vertical reading and was often associated with a distortion of the mire reflex. The change was high as +2.75 diopters. If greater than +1.00 diopter, it was associated with decreased visual acuity with forward correction and with the hydrophilic contact lenses. All but one of the patients who showedchanges of greater than +0.75 diopters over their baseline keratometer readings, were wearing their lenses on an average of 14-16 hours a day. The keratometer readings reverted to the baseline levels with a loss of the distrotion, if the patient reduced the wearing time to less than 12 hours daily. We believe that a maximum average daily wearing time of 12 hours is the safety limit required to minimize the development of induced corneal astigmatism.
mesh_terms: D000293:Adolescent; D000328:Adult; D001251:Astigmatism / Q000209:etiology*; D003263:Contact Lenses, Hydrophilic / Q000009:adverse effects*; D003315:Cornea; D005260:Female; D006801:Humans; D008297:Male; D013997:Time Factors; D014792:Visual Acuity