Outbreak of Fusarium Keratitis
On the 15th 2006, Bausch & Lomb (Rochester, New York) recalled its ReNu with MoistureLoc contact lens solutions from the worldwide market. This announcement, which followed a recall from the US market in April 2006, resulted from an outbreak of Fusarium keratitis associated with Bausch & Lomb’s contact lens solution. Fusarium keratitis is a vision-threatening fungal infection of the cornea. It is generally treated with antifungal medication, but can require corneal transplantation and may result in vision loss.
As of May 18, 2006, the Centers for Disease Control and Prevention (CDC) had received reports of 130 confirmed cases of Fusarium keratitis - and 31% had required corneal transplantation. Moreover, the outbreak has affected even more people worldwide, as cases were first identified in July 2005 in Hong Kong and Singapore. Left in the midst of these potentially frightening developments are the consumers who wear contact lenses, whether or not they used Bausch & Lomb products, and the ophthalmologists who treat them. To better understand the nature of the outbreak and for some insight into how ophthalmologists can respond, Medscape interviewed Editorial Board member Herbert Kaufman, MD, Boyd Professor of Ophthalmology, Pharmacology, Microbiology, and Neuroscience at Louisiana State University, New Orleans, Louisiana, and an expert in contact lens use and corneal infection. Here’s the transcript of the interview between Medscape and Dr Kaufman.
Medscape: What is Fusarium keratitis?
Dr. Kaufman: Fusarium is a fungus. Under normal circumstances, it is a rare cause of infection. Even though it’s spread around everywhere, it’s much more common - and infections from it are much more common - in warm, moist climates. In Florida, or Southeast Asia, for example, you would expect a much higher risk for Fusarium.
In the past, Fusarium infections were typically seen after vegetable injuries: orange growers, tea pickers at the tea harvest in China, that sort of thing, although they could occur at other times. They generally occur in younger people, and they typically occur more often in males.
What you need to get a Fusarium infection is, first, a high concentration of the fungus, and second, damage to the surface of the eye. In the case of contact lens use, ordinary contact lens use represents a minimal risk, although anything that damages the surface could have some risk.
More recently, Bausch & Lomb’s ReNu with MoistureLoc solutions represent a more serious risk because they hold fungus in a warm, moist setting, so that if there’s any contamination – particularly contamination of the lens case, which people often don’t clean - then the risk of getting fungus in the case and on this moisturized layer on the lens surface is greater. And these solutions, with the lens, can also cause minimal but significant damage to the surface of the cornea to the epithelium.
Medscape: What are the signs and symptoms that ophthalmologists should be aware of when examining their patients?
Dr. Kaufman: The typical patient with a fungus keratitis has pain, redness, light sensitivity, and decreased vision, and the ophthalmologist will notice a hazy area in the cornea. Sometimes the appearance of that is diagnostic. That is, there may be little spikes sticking out of the central cloudy area, out of the corneal ulcer - I’ve called these hyphate lines - or there may be satellite lesions. Occasionally, an endothelial plaque or an immune ring around the fungus occurs. But the most common tip-offs are these little linear extensions from what would otherwise be a round lesion. Also, patients with fungus keratitis tend to have a corneal ulcer on a cloudy area without the copious discharge and pus that you see with a bacterial infection. Not reliable, but a clue to the fact that it might be fungus.
Medscape: How is Fusarium keratitis treated?
Dr. Kaufman: The treatment of choice for Fusarium keratitis is a drug that I introduced many years ago called natamycin. Topical amphotericin B can also be used. Note that most drug stores don’t have natamycin, and so you need to get it from the manufacturer, Alcon.
Medscape: How often is corneal transplantation required and how successful is it?
Dr. Kaufman: Corneal transplantation is required if the scar in the center is large enough to obstruct vision, and that depends to a large extent on 2 factors. First, where is the ulcer? If it is off to the side of the cornea, not in a central optical axis, transplantation is typically not necessary. Second, it depends on how rapidly the treatment cures the fungus. Occasionally, therapy is ineffective and the infection must be surgically removed. Often, if there is a corneal ulcer in the center of the cornea, the patient will have reduced vision and glare. The question, then, is how bad is the vision, and how much the glare? Corneal transplants have a high success rate. Once the infection has quieted down and the eye is quiet, the success rate is probably over 90%.
Medscape: What can ophthalmologists tell their patients who are worried about infection? For example, are there any signs for which patients should seek immediate treatment? And is there any advice that can be given to help patients lower their risk?
Dr. Kaufman: The real risk of infection, and this epidemic, was caused by the peculiar properties of the Bausch & Lomb ReNu with MoistureLoc solution. Other contact lens solutions don’t cause this, and the risk of fungus keratitis with other solutions - whether from Bausch & Lomb or any other company - is incredibly small. This Moisture Loc solution has been taken off the market, but there might be some around somewhere, and patients should avoid it. On the other hand, any patient who has significant pain and redness in the eye or any blurring of vision ought to see an ophthalmologist as soon as possible.
Medscape: What should ophthalmologists do who have cases of Fusarium keratitis?
Dr. Kaufman: One of the hardest things to do is to diagnose it. Smears are taken, but if ordinary stains like Giemsa stains are used, they should not be heat-fixed but stained. If they’re cultured, the typical culture medium is Sabouraud’s media. But you need to be sure that it doesn’t have inhibitors, because for systemic or lung infections, inhibitors are put in to suppress the normal flora, and they will prevent growth of the fungus.
In addition to treating it properly, I think all cases at this time ought to be reported to the CDC, along with age and any inciting factor, such as contact lens wear and solution.
Medscape: Is there anything else that you would like to add regarding this crisis?
Dr. Kaufman: I think this crisis is pretty much over. The proximate cause - that is, the contact lens solution - has been identified. Exactly why this solution caused that and how to modify this solution are a subject of debate. But other contact lens solutions are clearly safe, and the use of contact lenses is safe. I would suggest that patients be meticulous in their cleaning of their contact lens cases. And if they’re going to leave a lens in solution longer than overnight, they ought to put it in the refrigerator.
References
US Food and Drug Administration. Bausch & Lomb global recall of ReNu with MoistureLoc contact lens cleaning solution. May 15, 2006. Available at http://www.fda.gov/bbs/topics/NEWS/2006/NEW01371.html.
Center for Disease Control and Prevention. Update: Fusarium keratitis - United States, 2005-2006. MMWR. 2006;55:1-2. Available at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm55d519a1.htm.
Herbert Kaufman, MD, Boyd Professor of Ophthalmology, Pharmacology, Microbiology, and Neuroscience, Louisiana State University, New Orleans, Louisiana
