Ocular Microbiology and Immunology Group
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2013 OMIG Abstract 16

A Model System for Testing the Effect of Biofilms on Drug Diffusion Through
Contact Lenses
K.M. Brothers; A. Nau; R.M.Q. Shanks
The Charles T. Campbell Laboratory, UPMC Eye Center, Department of Ophthalmology,
University of Pittsburgh School of Medicine, Pittsburgh, PA

Purpose: Bandage lenses are widely used when the epithelial surface of the cornea is compromised in cases of corneal abrasions, ulcers, penetrating corneal trauma, after anterior segment surgery, corneal prostheses and when pain relief is needed as in Thygeson’s punctate keratitis. It is known that biofilms readily grow on contact lenses in vivo.  Topical therapeutics such as antibiotics and steroids are frequently co-administered to patients using soft bandage lenses, and must pass through the contact lens to reach the cornea.  Our goal was to measure the impact of biofilms on drug delivery through contact lenses using an in vitro diffusion model.

Methods: Staphylococcus epidermis (ATCC 35984) biofilms were grown overnight on Air Optix Aqua (lotrafilcon A), and Kontur Precision Sphere lenses (methafilcon A) in brain heart infusion medium containing 0.2% glucose to an average of 3x10⁵ colony forming units per lens. Lenses were placed upright onto a 0.45 mm filter insert that remained hydrated with 1 ml phosphate buffered saline (PBS) below the filter insert.  Diffusion of therapeutics through lenses (+/- biofilms) into PBS was measured after 24 h at room temperature. Dexamethasone (40 µl of 6 mM) and fluorescein-conjugated dexamethasone were used as test therapeutics.  Diffused therapeutics were measured by absorbance or fluorescence and quantified using a standard curve.

Results: S. epidermis biofilms impeded passage of dexamethasone through both Air Optix and Kontur lenses by 44% and reduced diffusion of fluorescein-conjugated dexamethasone by 25%, (p<0.05, Student’s T-test).

Conclusions: We have developed a model to quantify diffusion of therapeutics through contact lenses. Using this model, it was shown that biofilms obstruct passage of a clinically relevant drug through two different contact lens types. These results highlight potential complications regarding the dosing of corticosteroids in patients who are wearing bandage contact lenses.

Disclosure: S=Research to Prevent Blindness, NIH grant AI085570, NIH Core Grant EY08098

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