Castroviejo Lecture 2009: 40 Years in Search of the Perfect Contact Lens

Abstract

Purpose-To identify the pathophysiological changes produced by contact lens wear that predispose the cornea to infection and search for prospective, modifiable risk factors that could reduce the incidence of this critical complication in millions of patients worldwide.Methods-Significant experimental and clinical publications are reviewed and the results of ongoing studies are presented.Results-Pseudomonas aeruginosa (PA) is the most common pathogen causing lens-related infectious keratitis over three decades. Contact lens wear can increase the risk of infection by increasing surface cell PA binding thereby promoting invasion between broken tight junctions (TJs), and initiating direct intracellular invasion mediated by lens-induced membrane lipid rafts. Prevention of upregulation of specific surface binding receptors for PA with concomitant increase in infection risk, is a Zero Damage Game where independent interactions between lens type, mode of wear, oxygen transmissibility, polymer and toxic effects of associated care solutions ideally should collectively produce no increased ability for PA to attach and/or to invade, thus minimizing the risk for lens-associated infections. The specific hypothesis tested is: "no increased epithelial surface damage…no increased PA binding or invasion…no increased risk for infection." Testing of this new paradigm has been performed in vitro, and in animal and human clinical trials and correlated clinically with relative risk results from robust current epidemiological studies. Results to date clearly support the use of lens-related increases in PA binding (bench) as a non-invasive clinical predictor of risk for lens-related infection in subsequent large scale population studies (bedside). Currently, results suggest that use of common commercial multi-purpose care solutions (MPS) with soft lenses may alone significantly increase infection risk by enhancing lens-related PA binding as compared to use of non-preserved solutions (hydrogen peroxide). Clinical testing also shows that only peroxide solutions show significant disinfection capability against amoebic cysts. Further case-control studies to examine relative risk for infection by lens type and lens care solution are urgently needed.Conclusions-Millions of patients are dependent on contact lenses for vision worldwide; and, over three decades lens use has increased while risk for lens-related infection has remained stubbornly unchanged. Unfortunately, recent introduction of a new generation of hyper oxygen transmissible lenses used with traditional MPS solutions has not lowered overall risks for lens-related infections; however, similar lenses used with non-preserved care solutions (peroxide) recently demonstrated no significant increases in PA binding in a one-year clinical trial. Collectively, these findings along with the urgent need for amoebic cysticidal disinfection, have led to a current recommendation to patients to use non-preserved (hydrogen peroxide) care solutions in soft lens wear. Over the past forty year...

Dry Eye Disease and Microbial Keratitis: Is There a Connection?

“…17 Epithelial anatomy (tight junctions, in particular) is one of several so-called innate immune response mechanisms that play a crucial role in preventing invasion of microorganisms into the ocular surface. 18–20 Innate responses are the first line of defense against infection, responding immediately but in a nonspecific manner to invading pathogens. 21, 22 Mucous membranes (eg, conjunctiva), secreted proteins (eg, lysozyme), mechanical barriers (eg, closure of eyelids), and the aforementioned physical barriers of the ocular surface epithelia, are just some features of the innate immune system at the ocular surface.…”

Insights to Using Contact Lenses for Drug Delivery

“…Considering that CL dropout is already a pressing problem for the CL industry [46][47][48], it may be difficult to convince a non-CL wearer to wear CLs, let alone wear it for extended periods. However, the CL market is anything but small, with approximately 140 million current CL wearers worldwide that could benefit from using this technology, should the need arise for therapeutic intervention [49,50]. In addition, many spectacle wearers who undergo refractive surgery are able to wear a bandage lens for a short period of time [14,17,18,51], demonstrating the potential shortterm success of a therapeutic lens to treat disease.…”

Tear exchange and contact lenses: A review

“…1,2 Despite the introduction of many new lens materials and care systems, dryness and discomfort continue to be reported by some 30---50% of lens wearers, particularly at the end of the day. 3---7 As a result of this discomfort, 30---50% of wearers will at some point lapse from lens wear 8---10 and 25% of wearers will permanently cease contact lens wear.…”