Predicting extended wear complications from overnight corneal swelling

Area of Science:

• Ophthalmology
• Optometry
• Corneal Physiology

Background:

• Extended wear (EW) of contact lenses, particularly rigid gas-permeable (RGP) lenses, necessitates understanding potential ocular complications.
• Corneal overnight swelling response (ONSR) is a physiological reaction to reduced oxygen permeability of contact lenses during sleep.

Purpose of the Study:

• To investigate whether ONSR serves as a reliable predictor for the development of ocular complications in patients undergoing 1-year of RGP contact lens EW.
• To assess the relationship between the degree of ONSR and the incidence of adverse ocular events.

Main Methods:

• A randomized, concurrently controlled clinical trial (Berkeley Contact Lens Extended Wear Study - CLEWS) involving over 200 subjects wearing RGP lenses for EW.
• Subjects were randomized to medium or high oxygen-permeable (Dk) RGP lenses after adaptation to EW.
• Clinical assessments, keratometry, and corneal pachometry were performed at 3-month intervals over 1 year.

Main Results:

• ONSR demonstrated a direct correlation with lens oxygen permeability (Dk) (P = 0.01) and significant inter-subject variability.
• No statistically significant difference in complication-free probability was observed between subjects with mild ONSR and those with greater corneal edema (P = 0.84).
• The risk of developing keratopathy was not significantly associated with the ONSR (relative risk = 1.00).

Conclusions:

• The corneal ONSR is not a suitable predictor for ocular complications associated with 1-year of RGP contact lens EW.
• Contact lenses inducing minimal or no corneal edema during overnight wear are not inherently safer for extended wear.