Customized contact lens treatments for in-the-eye medication
Fick, James M
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Hydrophilic polymer (polymacon, alphafilcon-A) and silicone-based (balafilcon-A) hydrogel contact lenses, before and after surface modification by radio-frequency glow-discharge treatment (RFGDT), were used to monitor methylene blue/silver nitrate drug-surrogate uptake and elution. The drug-loading protocol included ethyl alcohol-swelling delivery into silicone/hydrocarbon compartments and then osmotic delivery into water-dominated compartments. Light and scanning electron microscopy (SEM) were employed to examine the drug-surrogate distributions throughout the lens specimens and revealed a presence of superficial/subsurface deposits of silver and methylene blue. Infrared spectroscopy revealed modified absorption peaks, accordingly. Energy-dispersive x-ray (EDX) analysis and inductively coupled argon plasma atomic emission spectroscopy (ICP) confirmed silver lens depot concentrations and were employed to measured eluate concentrations, while visible spectrophotometry and ICP spectrometry monitored methylene blue and silver elution rates in static versus simulated eye-blinking conditions. Laboratory results confirmed the feasibility of using ethyl alcohol as a potential swelling agent, and the practicality of using RFGDT, SEM, EDX, ICP, and visible spectrophotometry methods as potential analysis instruments for methylene blue and silver concentrations. The differential diffusion rates of drug surrogates from the RFGDT versus as-manufactured silicone-hydrogel (balafilcon-A), alphafilcon-A, and polymacon were compared at each experimental condition using ANOVA statistics. The conclusions reached are that (1) initial drug uptake of surface modified lenses increased in this order: polymacon < alphafilcon-A < balafilcon-A lenses; (2) drug release rates of the polymacon, and alphafilcon-A remained unaffected by the RFGDT; (3) increased release rates occurred from the RFGDT-surface-modified balafilcon-A lenses; and (4) dynamic forces increased the release rates for all contact lenses.