Abstract.Based on measurements of the corneal diameter, radius of curvature variation, and thickness profile a method for calculation of the horizontal meri‐ dian's sectional tissue mass area (M) is described. Pooled values of 52 normal eyes demonstrate M to be 8.57 mm2±SD. Comparing one eye of 27 keratoconic patients with one eye of 28 normals established no significant difference in M. This result is in accordance with a hypothesis in which the keratoconic corneal thinning is a result of an increased sliding of collagen fibers rather than a result of increased collagen de‐ grada