Measurement of corneal swelling variations without removal of the contact lens during extended wear.

Purpose: To validate the use of noncontact scanning slit pachymetry and OCT pachymetry measurements without contact lens (CL) removal, to determine corneal swelling variations during extended wear (EW).

Methods: Central corneal thickness (CCT) was measured with ultrasonic (US) pachymetry, noncontact scanning slit pachymetry (Orbscan II; Bausch & Lomb, Tampa, FL), and optical coherence tomography (OCT) 1 week before the wearing of CLs and during 1 week of EW. High-Dk (lotrafilcon A) and low-Dk (etafilcon A) soft CLs were randomly fitted for EW in the right and left eyes of 20 subjects with normal ocular health. Orbscan and OCT were also performed without CL removal after 3 and 7 days of wear.

Results: CCT measured with Orbscan and OCT showed a high correlation with US pachymetry. There were corneas with edema and without edema. Bland-Altman analysis showed a high level of agreement between Orbscan and OCT, with and without CL removal and with US pachymetry. High repeatability of Orbscan (r(2) = 0.000) and OCT (r(2) = 0.001) measurements without CL removal was also found. Etafilcon A lenses induced significantly higher corneal swelling than did lotrafilcon A lenses measured with Orbscan and OCT.

Conclusions: Orbscan and OCT are accurate, noninvasive, and reproducible techniques for evaluation of CCT without CL removal. OCT has more accuracy and repeatability than does Orbscan. Both techniques allowed for measurement throughout the study period of the CCT differences induced by CL wear.