- Corneal pachymetry ≤ 400 microns at the thinnest point measured by Pentacam in the eye(s) to be treated when the isotonic riboflavin solution is used or ≤ 300 microns when the hypotonic riboflavin us used, provided that the corneal thickness after treatment with the hypotonic riboflavin solution is > 400 microns. Corneal pachymetry ≤ 450 microns at the proposed insertion site for the Intacs