Until now, fungal keratitis has been rarely reported in the healthy soft contact lens wearing population. Historically, the vast majority of contact lens related microbial keratitis has been caused by bacterial pathogens such as Pseudomonas aeruginosa.
Fungal organisms include the single cells yeasts like Candida, and multi-cellular filamentous fungi, such the Fusarium species recently associated with fungal keratitis in contact lens wearers. Fungal keratitis has typically occurred after trauma associated with plant matter and was more commonly encountered in immune compromised individuals and those with chronic ocular surface disease. Fungal infections are more prevalent in warmer climates such as South Florida. The higher incidence of fungal keratitis among otherwise normal contact lens wearers is new finding.
The classic description of fungal keratitis is a grayish-white corneal infiltrate with a rough, dry texture and feathery borders. Satellite lesions are common and hypopyon and endothelial plaque may also be observed. Intact and slightly elevated epithelium overlying a deep stromal infiltrate may also be seen.
Despite these somewhat unique characteristics, it is often difficult to clinically differentiate between fungal and bacterial keratitis. For that reason many clinicians believe that antifungal therapy should be preceded by antibiotic therapy and initiated only after the diagnosis is established by positive corneal culture, corneal tissue biopsy, or confocal microscopy. Microscopic evaluation of corneal scrapings may also reveal fungal elements.
Natacyn (natamycin 5%) is the only commercially available topical agent indicated for the treatment of fungal keratitis. It is often effective against filamentous fungi such as Fusarium. Other therapeutic agents include a variety of topical and oral anti-fungal medications.
Steroid and combination agents containing steroids should never be used unless a definitive diagnosis has been well established, the infection is well under control, inflammation is a major factor increasing morbidity and the benefits of using a steroid clearly outweigh the substantial risks. Under the current advisory, all clinicians should be especially vigilant. Approach suspicious ulcers with caution; when presumed bacterial keratitis does not respond rapidly to appropriate antibiotic therapy, fungal infection should be suspected. Delayed treatment may worsen the course of the disease and the patient's prognosis.
Patients are likely to become increasingly aware of this health issue, making communication critical. Staff should be educated regarding the current situation and be able to manage patient questions and concerns. They should be aware that the risk of developing fungal keratitis is extremely small. There are over 30 million contact lens wearers in the United States and fewer than 30 cases of fungal keratitis have been reported in the US during this recent outbreak. Still, patients with signs or symptoms of microbial keratitis should be scheduled immediately. Indications that a patient may have microbial keratitis include:
Patients who call in with these symptoms should be advised to remove their lenses immediately and to seek care as soon as possible.
Although still under intense investigation, the only identifiable risk other than contact lens wear is poor hygiene. This is an excellent time to reinforce proper lens care including the following steps:
More detailed information to follow.