Abstract
Purpose :
Wounds of the corneal epithelium typically result in severe ocular pain. Tetracaine eye drops inhibit the sensation of corneal pain, however the effect is short lasting and therefore the drops must be reapplied several times an hour. Due to the concern of delayed wound healing associated with repeated use, tetracaine eye drops are not prescribed for self-administration. To provide an alternative, we developed and evaluated tetracaine-eluting contact lenses (TCLs) that provide sustained and controlled tetracaine release.
Methods :
TCLs were created by encapsulating a tetracaine-polymer film within a hydrogel material (methafilcon A) commonly used for contact lenses. In vitro drug release studies were performed by immersing three different TCL formulations in phosphate buffered saline under infinite sink conditions. Efficacy from the TCL formulations was evaluated in normal rabbit eyes at predetermined time points using a Cochet–Bonnet esthesiometer, which indirectly measures the corneal sensation threshold (CST). Efficacy of TCLs were compared to vehicle contact lenses (VCL) that lacked any drug. The effect of TCLs on corneal re-epithelialization was assessed by creating a 6mm diameter corneal epithelial wound followed by the immediate placement of TCLs or a commercial contact lens wear also composed of methafilcon. The diameter of the corneal epithelial defects was measured at creation, and at 2, 4 and 7 days.
Results :
Three doses of TCLs demonstrated sustained release of a total of 240, 600, and 900 µg for low, medium, and high doses, respectively. For the low and medium doses, TCLs reduced CST for 5 hours, while the high dose reduced CST for 24 hours compared to VCLs (p<0.05, n=5/group). Corneal epithelial wound healing studies in rabbits showed 80% closure at day 2 with no significant difference compared to rabbits wearing commercial contact lenses, with most rabbits fully healed by day 4 (n=4/group).
Conclusions :
The TCL provided reduced corneal sensation in rabbits for up to 24 hours and demonstrated no delays in corneal epithelial wound healing.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.