Mycotic Keratitis and Lens Care
BY MICHAEL A. WARD, MMSC, FAAO
As I write this column, the U.S. Food and Drug Administration and Centers for Disease Control and Prevention are actively investigating cases of Fusarium keratitis among contact lens wearers who reported using Bausch & Lomb's ReNu with MoistureLoc MPS formulation. It's probable that by the time you read this article, the cause of this outbreak will have been discovered and remedied.
Figure 1. Mycotic keratitis
Mycotic (fungal) keratitis (Figure 1) is an uncommon complication of contact lens wear. At least 35 genera of fungi have been historically associated with corneal disease. The genera Candida, Fusarium, Cephalosporium and Aspergillus are the most commonly reported causative agents in fungal keratitis in the United States.
Fungi prefer tropical (warm and humid) environments, which is consistent with their greater reported prevalence in the Southeastern United States. The true incidence is unknown because fungal keratitis is not a reportable disease. However, retrospective studies provide some insight as to the spectrum of fungal keratitis. Rosa et al (1994) reported that Fusarium sp accounted for 62 percent of 151 cases of fungal keratitis in south Florida over a 10-year period (1982 to 1992) and revealed that the most common risk factor is trauma, including contact lens wear.
Tanure et al (2000) at Wills Eye Hospital reviewed 24 cases in Philadelphia between 1991 and 1999, and reported Fusarium sp as the most common filamentous fungus and Candida sp as the most frequent cause of fungal keratitis. The two most common predisposing factors in the Philadelphia study were chronic surface disease (41.7 percent) and contact lens wear (29.2 percent).
Ritterband et al (2006) at New York Eye and Ear Infirmary reviewed their clinical experience in New York over a 16-year period (1987 to 2003) and identified 61 cases of fungal keratitis. The reported risk factors in New York were different from previous reports, identified as HIV positivity (24.6 percent) and chronic surface disease (22.6 percent), followed by trauma, H. simplex keratitis and lens wear. Other investigations reported risk factors that include extended wear and lens wear during water activities.
Treatment and Prevention
Fusarium solani is reportedly the most virulent and drug resistant of the 20-plus species of the Fusarium genera. Topical administration of natamycin 5% appears to be the mainstay of treatment, with amphotericin B, ketoconazole and itraconazole reported as adjunctive therapies. Penetrating keratoplasty is required in some cases.
Cases of contact lens-associated corneal ulcers are devastating to affected patients and practitioners and injurious to our industry. What's more, most lens-associated corneal ulcers are preventable with proper practitioner instruction coupled with patient compliance with the instructions. Lens care instructions should include hand washing, daily use of fresh solutions (do not top-off), daily rinsing and air drying of storage cases, regularly replacing storage cases and scalding the case weekly with freshly boiled water. In addition, patients should replace lenses as prescribed and avoid wearing contact lenses during water activities.
For references, please visit www.clspectrum.com/references.asp and click on document #128.
Mr. Ward is an instructor in ophthalmology at Emory University School of Medicine and Director, Emory Contact Lens Service.