PURPOSE. Silicone-hydrogel (SH) contact lens materials are stiffer and possess substantially greater oxygen transmission characteristics than conventional polymers. These characteristics provide SH lenses with obvious potential as bandage lenses. The objective of this in vitro study was to evaluate the ability of SH materials to absorb and release topical ocular medication in a controlled manner, with a view to assessing their potential use as novel drug delivery systems when being used as bandage lenses. METHOD. Triplicate drug adsorption and desorption trials were undertaken using 0.15% ciprofloxacin (Sigma). Materials: Acuvue (Vistakon), Soflens 66, Optima and PureVision (Bausch&Lomb), Focus Night&Day and Focus Monthly (CIBA Vision) and Proclear Compatibles (Biocompatibles). Lenses (–1.50D) took up drug by soaking in 2 ml of drug dissolved in buffered saline (Unisol 4; Alcon) for 24 hours. Drug concentration was measured by spectrofluorimetry (excitation: 324nm, emission: 440nm). Drug release was measured after transferring the lenses to 2 ml of buffered saline.
RESULTS. Maximum drug uptake, an average of 1800 µg drug per lens, was achieved within 1 hour with all materials. No significant difference between the lenses was observed. Significant differences were seen in the release behaviour (p<0.001). Proclear (217 µg/lens) released most drug followed by Optima > Focus Monthly > Acuvue > Soflens > PureVision (80µg/lens) > Focus Night&Day (65 µg/lens).
CONCLUSIONS. Both of the currently available SH lenses show favourable drug loading. All lenses, many of which have already been used as in eye drug delivery devices, released an amount of drug comparable to that administered with eye drops. The exceptional oxygen transmission characteristics of SH materials warrant further in vitro and in vivo studies to determine their applicability as sustained release drug delivery devices and/or therapeutic/bandage lenses.