Effects of rigid contact lens truncation on oxygen access to the central cornea under static and dynamic conditions

Truncation is most commonly used for stabilization of bifocal and toric front surface lenses. Lenses with small edge defects also can be truncated and polished rather than being discarded. The purpose of this study was to determine whether corneal physiology is compromised when truncated lenses are worn. Contact lenses were manufactured with three amounts of truncation (0, 0.2, and 0.4 mm) in two contact lens materials (polymethylmethacrylate and itabisfluorofocon A). All lenses were fitted “on K” on the right eye of each of six subjects, with all other parameters kept constant. As expected, central corneal oxygen uptake rates measured with the itabisfluorofocon A material were significantly lower, indicating less hypoxic stress or oxygen deprivation, than those measured with polymethylmethacrylate across conditions (nonblink and blink) and amounts of truncation. No significant differences in central corneal oxygen uptake were found among amounts of truncation across conditions and materials.