On the conformity of soft lenses to the shape of the cornea.

The assumption that a properly fitted soft contact lens conforms to the shape of the cornea in the central region was tested by measuring the apparent radius of curvature of the back surface of various soft contact lenses on the eye, with a high illumination keratometer. Real radius of curvature was calculated by means of an appropriate formula. It was found that soft lenses conform closely to the corneal shape. The mean difference between the radius of the back surface of the lens and corneal radius of curvature was +0.015 mm in the horizontal meridian, and +0.023 mm in the vertical meridian. The lenses were slightly flatter than the cornea in each meridian. The difference in conformity between the horizontal and vertical meridians was not significant. Slight differences were found in the degree of conformity of the three soft contact lens designs studied. The thicker, lower water content lenses showed slightly less conformity.