As the dust begins to settle after the outbreak of fungal eye infections among contact lens wearers and attention turns to the lessons the industry can learn from the experience, further studies have been published on the safety of contact lenses and the risks compared to laser refractive surgery.
It was back in August that the Centers for Disease Control and Prevention (CDC) published the results of its investigation into the US cases of Fusarium keratitis (News, August 24). Chang et al (1) identified 164 confirmed cases, of whom 154 wore soft contact lenses. Although these cases were significantly more likely than controls to report using ReNu with MoistureLoc, Fusarium was not recovered from the factory, warehouse, solution filtrate or unopened solution bottles.
The authors concluded that these cases were associated with the use of ReNu with MoistureLoc but the mechanism was unclear. They say that further studies may help to determine if the infections were caused by an interaction of the solution's ingredients with Fusarium that might have permitted growth of the organism.
RUBBING RECOMMENDED
In the CDC study, no single hygiene practice was independently associated with disease, but poor hygiene practices were common and similar among case patients and controls. Re-using solution already in the lens case was a significant factor, the authors said.
An editorial (2) in the September issue of Contact Lens & Anterior Eye by Snyder of the University of Alabama, looked at the implications of the outbreak for lens care product manufacturers and, in particular, for patients' lens care and handling procedures. Snyder said he had always recommended the 'rub' step for his patients and would welcome less emphasis on 'no rub' along with the inclusion of 'rub' instructions on lens care product labelling in future.
When patients were compliant in properly managed contact lenses by following the appropriate protocol with an approved lens care system, the chances for complications, including infections, were minimised, he said.
INFECTIONS INCREASING
While recent publications have focused on fungal infections, a paper published by Joslin and co-workers (3) in the American Journal of Ophthalmology reported an outbreak of Acanthamoeba keratitis (AK) among contact lens wearers in Chicago.
The retrospective, population-based study compared all AK cases diagnosed at the University of Illinois from June 2003 to November 2005 with historical cases from June 2000 to November 2002. Among the 40 recent cases, 95 per cent of patients wore contact lenses. Current AK diagnosis rates were significantly higher than historical rates, leading the authors to conclude that AK cases are increasing in frequency.
Meanwhile, researchers in Belgium have found that the number of patients requiring hospitalisation for contact lens-related corneal ulcers is increasing. Verhelst and colleagues (4) at the University of Antwerp Hospital analysed files of patients hospitalised for contact lens-induced corneal ulcers in the eight Belgian university hospitals from January 1997 to December 2003.
A total of 107 patients were documented and the number of cases rose from five in 1997 to 22 in 2003, an increase only partially explained by the increasing prevalence of lens wearers. A total of 99 subjects used soft contact lenses, of whom nine used disposables, 73 planned replacement and 17 conventional lenses. Only six patients used extended wear lenses and three used daily disposable lenses.
A further reminder that contact lens infection can occur in daily disposable users comes in a case report in the December issue of Contact Lens & Anterior Eye (5). A 70-year-old man presented to the Norfolk and Norwich University Hospital with a red eye, reduced vision and corneal epithelial changes. AK was not suspected initially because the patient wore daily disposable contact lenses, leading to a 17-day delay in initiating treatment.
The authors conclude that AK can occur in patients who re-use daily disposable lenses. They warn that this diagnosis can be difficult to make and suggest it should be considered in all patients who wear contact lenses, including daily disposables. All daily disposable users should be reminded that the benefits of this modality are only possible if patients wear the lenses once and throw them away, they say.
RISK OF LASIK versus CLs
Alongside this series of papers on contact lens-related infections, a letter in the October issue of Archives of Ophthalmology from Mathers and co-workers (6) compared the risks of refractive surgery with those of contact lens wear (News, October 13). The authors used previous studies to estimate the rate of infection with each form of vision correction.
They estimate the lifetime risk of bacterial keratitis over 30 years at one case per 100 for daily-wear contact lenses and a lifetime risk of vision loss to 20/70 of one in 2,000. In contrast, the authors used a study conducted among US Army personnel to propose that the incidence of vision loss greater than two lines following refractive surgery may be one case per 10,000.
Mathers et al concede that these calculated risks are approximate and note that highly oxygen permeable contact lenses should lessen the risks for contact lens wear, although laser surgery will also become safer. They also acknowledge that the data sets used to estimate risks cannot be compared directly and long versus short-term risks are difficult to equate. However, despite these limitations, they conclude that the relative risk of vision loss from refractive surgery and contact lenses may need to be reassessed.
? To access the abstracts and full text of these papers go to www.ncbi.nih.gov/entrez/ and search by author's name. Papers published in Contact Lens & Anterior Eye, the journal of the British Contact Lens Association, can be accessed free online by BCLA members, who also receive six free issues of the journal per year. CLAE is published by Elsevier, a sister company to Reed Business Information, publisher of Optician.
REFERENCES
1 Chang DC, Grant GB, O'Donnell K et al. Multistate outbreak of Fusarium keratitis associated with use of a contact lens solution. JAMA, 2006296:8 953-963).
2 Snyder C. Lens care complications - where's the rub? CLAE, 2006 29:4 161-162.
3 Joslin Epidemiological characteristics of a Chicago-area Acanthamoeba keratitis outbreak. Am J Ophthalmol, 2006142:2 212-7.
4 Verhelst D, Koppen C, Van Looveren J et al. Contact lens-related corneal ulcers requiring hospitalization: A seven-year retrospective study in Belgium. Acta Ophthalmol Scand, 2006:84:4 522-6.
5 Niyadurupola N and Illingworth CD. Acanthamoeba keratitis associated with misuse of daily disposable contact lenses. CLAE, 2006 29:5 269-71.
6 Mathers WD, Fraunfelder FW and Rich FR. Risk of Lasik surgery vs contact lenses. Arch Ophthalmol, 2006124:10 510-11.