The effect of long-term, daily contact lens wear on corneal sensitivity

Purpose. To assess the effect of long-term, daily-wear soft contact lenses and rigid gas permeable (RGP) contact lenses on corneal sensitivity using a noninvasive, air-pulse stimulus. Methods. The central and peripheral (temporal, medial, inferior) corneal sensation thresholds of 40 non-lens wearers, 40 soft lens wearers, and 40 RGP lens wearers were assessed using the Non-Contact Corneal Aesthesiometer (NCCA). The individuals who wore contact lenses were grouped according to the number of years of lens wear (10 years or less, 11-20 years, and 21 years or more). Results. Although a significant reduction in corneal sensitivity was found between the contact lens wearers and non-lens wearers (p = 0.000), no difference was found between the two lens-type subgroups (p = 0.939). This pattern of significance was repeated at each of the peripheral test locations. No relationship between corneal sensitivity and years of lens wear was found centrally (r(2) = 0.001) or at any of the peripheral test locations. No significant difference was found between the central corneal sensation thresholds for the different subgroups of lens wear duration (p = 0.469) or for any of the peripheral test locations. Conclusions. Both soft and RGP lens wear produce a similar type of corneal sensitivity loss, although the mechanism for this loss is different for the two lens types. The extent of sensitivity loss is not related to the duration of lens wear and appears to plateau after the first few months of wear. No topographical variation in sensitivity loss was found with lens type or with the duration of lens wear.