Laser eye surgeries like LASIK and especially photorefractive keratectomy (PRK) can be painful on the eyes for a few days following the procedure. To alleviate the pain anesthetic eye drops are used, which have to be regularly administered by the patient. Not only is that inconvenient, but one can actually overdose a bit on them drops.
Now researchers at University of Florida are reporting that they developed a way to load topical anesthetics into contact lenses to provide extended delivery of pain relief in a uniform fashion. And since many of the patients that undergo eye procedures have been wearing contacts prior, they’re already used to putting them on.
From the study abstract in Langmuir:
Here we focus on creating dispersion of highly hydrophobic vitamin E aggregates in the lenses as barriers for drug diffusion for increasing the release durations. This approach has been shown previously to be successful in extending the release durations for some common hydrophilic ophthalmic drugs. The topical anesthetic drugs considered here (lidocaine, bupivacaine, and tetracaine) are hydrophilic at physiologic pH due to the charge, and so these cannot partition into the vitamin E barriers. However, these surface active drug molecules adsorb on the surface of the vitamin E barriers and diffuse along the surface, leading to only a small decrease in the effective diffusivity compared to non-surface-active hydrophilic drugs. The drug adsorption can be described by the Langmuir isotherm, and measurements of surface coverage of the drugs on the vitamin E provide an estimate of the available surface area of vitamin E, which can then be utilized to estimate the size of the aggregates. A diffusion controlled transport model that includes surface diffusion along the vitamin E aggregates and diffusion in the gel fit the transport data well. In conclusion, the vitamin E loaded silicone contact lens can provide continuous anesthetics release for about 1–7 days, depending on the method of drug loading in the lenses, and thus could be very useful for postoperative pain control after corneal surgery such as the photorefractive keratectomy (PRK) procedure for vision correction.
American Chemical Society press release: Contact lenses provide extended pain relief to laser eye surgery patients
Abstract in Langmuir: Transport of Topical Anesthetics in Vitamin E Loaded Silicone Hydrogel Contact Lenses