The Berkeley Contact Lens Extended Wear Study: Part II - Clinical results

Objective: To describe the principal clinical outcomes associated with 12 m onths use of rigid gas-permeable (RGP) extended wear contact lenses and add ress two primary study questions: (1) does extended wear (EW) of high oxyge n transmissibility (Dk/t) RGP lenses reduce the incidence of ocular complic ations, and (2) does the wearing of high-Dk/t lenses reduce the rate of fai lure to maintain 6-night RGPEW over 12 months? Design: A randomized, concurrently controlled clinical trial. Intervention: Subjects who adapted to EW with high Dk (oxygen permeability) RGP lenses were randomized to either high Dk or medium-Dk RGP lenses for 1 2 months of 6-night EW. Main Outcome Measures: Contact lens-associated keratopathies (CLAK), change s in refractive error and corneal curvature, and survival in EW. Results: Two hundred one subjects were randomized to medium or high-Dk lens es for 12 months of EW. Sixty-two percent of the subjects in each group com pleted 12 months of EW; however, the probability of failure was significant ly greater for the medium-Dk group. Although the risk of complications was similar for the two groups, the number of CLAK events that led to terminati on were 16 versus 5 for the medium-Dk and high-Dk groups, respectively. Thi s suggests that the type of adverse response or the inability to reverse an adverse event was different for the group being exposed to the lower oxyge n dose. Conclusions: The level of oxygen available to the cornea has a significant impact on maintaining successful RGP extended contact lens wear, but not on the initial onset of CLAK. The number of clinical events leading to termin ation was substantially higher for the medium Dk group, which suggests that corneal hypoxia is an important factor in the development of CLAK. Althoug h overnight contact lens wear should be recommended with caution and carefu lly monitored for early detection of ocular complications, it appears that high-Dk RGP lenses can be a safe and effective treatment for correction of refractive error for most individuals who can adapt to EW. Ophthalmology 20 01;108:1389-1399 (C) 2001 by the American Academy of Ophthalmology.