BASIC INVESTIGATION Prevention of Bacterial Colonization of Contact Lenses With Covalently Attached Selenium and Effects on the Rabbit Cornea Steven M. Mathews, OD, PhD,* Julian E. Spallholz, PhD,† Mark J. Grimson, PhD,‡ Richard R. Dubielzig, DVM,§ Tracy Gray, BA,* and Ted W. Reid, PhD* Purpose: Although silicone hydrogel materials have produced many corneal health benefits to patients wearing contact lenses, bacteria that cause acute red eye or corneal ulcers are still a concern. A coating that inhibits bacterial colonization while not adversely affecting the cornea should improve the safety of contact lens wear. A covalent selenium (Se) coating on contact lenses was evaluated for safety using rabbits and prevention of bacterial colonization of the contact lenses in vitro. Methods: Contact lenses coated with Se were worn on an extended-wear schedule for up to 2 months by 10 New Zealand White rabbits. Corneal health was evaluated with slit-lamp biomicroscopy, pachymetry, electron microscopy, and histology. Lenses worn by the rabbits were analyzed for protein and lipid deposits. In addition, the ability of Se to block bacterial colonization was tested in vitro by incubating lenses in a Pseudomonas aeruginosa broth followed by scanning electron microscopy of the contact lens surface. Results: The covalent Se coating decreased bacterial colonization in vitro while not adversely affecting the corneal health of rabbits in vivo. The Se coating produced no noticeable negative effects as observed with slit-lamp biomicroscopy, pachymetry, electron microscopy, and histology. The Se coating did not affect protein or lipid deposition on the contact lenses. Conclusion: The data from this pilot study suggest that a Se coating on contact lenses might reduce acute red eye and bacterial ulceration because of an inhibition of bacterial colonization. In addition, our safety tests suggest that this positive effect can be produced without an adverse effect on corneal health. Key Words: contact lens, bacterial colonization, selenium (Cornea 2006;25:806–814) C ontact lenses are worn by approximately 90 million people worldwide. 1 Early contact lenses had to be taken out of the eye daily for removal of accumulated protein and lipids discharged by the eye and for sterilization. In addition, poor oxygenation of the cornea, caused by the relatively low oxygen transmissibility of early conventional hydrogel lenses, also limited wearing time. Although nearly all contact lens wearers still remove their lenses daily, the recent arrival of silicone hydrogel lenses, which provide greater oxygen transfer to the cornea, allow the longer-term 30-day wear that is now permitted by the Food and Drug Administration (FDA). However, despite the improved corneal physiology provided by the new highly oxygen-permeable 30-day lenses, bacteria that cause acute red eye or even corneal ulceration are still a clinical concern. When a contact lens is placed on the eye, the surface of the contact lens is colonized by bacteria more than 50% of the time. 1,2 The role that this colonization plays in the success of contact lens wear has been a topic of interest for decades. Studies that look at this issue generally fall into 2 categories: studies that have an interest in the characteristics of the bacterial colonization in asymptomatic patients and studies that looked at bacterial colonization in patients with acute red eye or infection. Several earlier studies 2–9 used culturing techniques or scanning electron microscopy (SEM) to look at bacteria that are loosely and/or tightly bound to contact lenses taken from asymptomatic patients. There seems to be general agreement across studies to date that the makeup and density of bacterial colonization do not change with changes in the contact lens material. 8,9 How the number of bacteria varies over time and wearing schedule remains less clear. 5–10 Acute inflammatory reactions or infections have been reported to be associated with bacterial colonization of the soft contact lens surface, particularly when the lenses are worn for extended periods. 10–18 Although microbial keratitis does not seem to be exclusively associated with bacteria of a particular Gram stain, gram-negative bacteria seem to be asso- ciated with contact lens–induced acute red eye (CLARE), 10,12,13 and gram-positive bacteria are associated with contact lens– induced peripheral ulcers. 15 Baleriola-Lucas et al 10 found a clear association between acute red eye responses in extended-wear Received for publication February 24, 2005; revision received November 9, 2005; accepted February 5, 2006. From the *Department of Ophthalmology and Visual Sciences, Texas Tech University Health Science Center, Lubbock, TX; the †Department of Nutrition, Texas Tech University Health Science Center, Lubbock, TX; the ‡Department of Biological Sciences, Texas Tech University Health Science Center, Lubbock, TX; and the §Department of Pathobiological Sciences, University of Wisconsin, School of Veterinary Medicine, Madison, WI. Supported by Vistakon Research Grant from the American Optometric Foundation. Reprints: Steven Mathews, OD, PhD, Texas Tech UHSC–Ophthalmology, 3601 4th Street, Lubbock, TX 79430 (e-mail: steven.mathews@ttuhsc.edu). Copyright Ó 2006 by Lippincott Williams & Wilkins 806 Cornea  Volume 25, Number 7, August 2006