Corneal Sensitivity with Contact Lenses of Different Mechanical Properties

Purpose. To examine the changes in corneal sensitivity after overnight wear of contact lenses with different mechanical properties. Methods. Twenty young-adult subjects wore a silicone hydrogel, rigid gas-permeable, or orthokeratology (OK) contact lens in randomized order for a single night of wear in the right eye only. All lenses were matched in Dk/t (similar to 46 ISO Fatt). Changes in corneal apical radius r(o), asphericity Q, and corneal refractive power (Medmont E300) were measured. Changes in central corneal sensitivity were also measured by a masked investigator using two instruments: Cochet-Bonnet (COBO) aesthesiometer and Non-Contact Corneal Aesthesiometer (NCCA). Results. There were significant differences in corneal topographic change from baseline between the lens types for ro, Q, and corneal refractive power. There were also significant differences in the change from baseline (mean +/- SD) in corneal sensitivity between lens types using the COBO (silicone hydrogel, 0.02 +/- 0.17 g/mm(2); rigid gas-permeable, 0.03 +/- 0.20 g/mm(2); OK, 0.22 +/- 0.33 g/mm(2)). A significant increase in threshold from baseline was only seen in the OK lenses (p = 0.006). There was no change in sensitivity thresholds from baseline for any lens type using the NCCA (p > 0.05). Conclusions. Central corneal sensitivity is reduced after a single overnight wear of OK lenses, as measured using the COBO aesthesiometer. This suggests that the mechanical force exerted by contact lenses may influence corneal sensitivity.