Artifact in optical pachometry with contact lenses in situ

We describe a measurement artifact associated with the wearing of a contact lens during optical pachometry. The contact lens essentially magnifies the image of the cornea, creating a nonphysiological apparent increase in corneal thickness. This artifact ranges from 0.27 to 1.22% with four current extended wear hydrogel lenses, depending on lens thickness and index of refraction. The implications of this artifact are discussed relative to study design and interpretation of results for contact lens-induced corneal edema.