Early Intervention Improves Outcomes in Fungal Keratitis

Difficult access to natamycin continues to hinder treatment. Dermot McGrath reports.

Eyes with yeast fungal keratitis were shown to have better clinical outcomes than eyes with filamentous keratitis in a large-scale retrospective study carried out over 15 years at a Portuguese centre.

“Our study also showed commencement of antifungal therapy within 72 hours of clinical onset was associated with greater visual acuity improvement,” said Rosa Pinheiro MD.

Fungal keratitis is considered one of the major causes of ocular morbidity, particularly in developing countries, she explained.

“Recent reports in the scientific literature indicate the incidence is increasing in temperate regions such as Portugal. While the risk factors are well known, there are fewer largescale studies of fungal keratitis compared to bacterial keratitis.”

Although the recent Mycotic Ulcer Treatment Trial (MUTT) did study the outcomes of various treatment regimens for filamentous mycotic keratitis, the topical natamycin used in that study is not readily available in Portugal.

Dr Pinheiro’s retrospective study compared risk factors, clinical features, and management outcomes of culture-proven filamentous and yeast fungal keratitis. The team identified all cases of fungal keratitis from the microbiologic records between 2005 and 2020 at Coimbra University Hospital in Portugal. They noted demographic data, risk factors, logMAR visual acuity (VA), therapeutic management, and functional outcomes.

Of the 49 eyes of 49 patients identified with fungal keratitis, 33 had filamentous fungus (group 1), and 16 had yeast fungus (group 2). The most prevalent fungi were fusarium and aspergillus (group 1), while candida was the most prevalent for those with yeast fungus (group 2). Patients with filamentous fungi had significantly better visual acuity at presentation and a greater visual acuity improvement following treatment.

The most prevalent risk factors overall were systemic diseases (62%), previous ocular surgery (41%), and penetrating keratoplasty (34%).

“These are all well-known predisposing factors to fungal keratitis. Penetrating keratoplasty was performed in 43% of our patients and is considered an effective treatment for fungal keratitis that does not respond to antifungal medication,” Dr Pinheiro said. The overall enucleation rate of 16% compared favourably to a previous Portuguese study that reported a rate of 28%.

No correlations were found between filamentous and yeast fungi and contact lens use, history of trauma or surgery, corneal perforation, and previous penetrating keratoplasty. Interestingly, initiation of antifungal therapy within 72 hours of clinical onset was associated with a greater visual acuity improvement, Dr Pinheiro said.

“Antifungal therapy took an average of eight days to prescribe, but in 31% of patients, it was administered empirically within the first 72 hours of onset. This turned out to be the only predictive factor of greater visual acuity improvement.”

Sorcha Ní Dhubhghaill MD, PhD underscored the problem many treating physicians in European countries had in sourcing topical natamycin at an economically viable price. “It is produced in such small quantities that the manufacturers charge something in the range of 400 to 500 euros per 15 mL bottle, yet it is so cheap and readily available in other countries,” she said.

Bruce Allan MD confirmed there were no problems of availability in the United Kingdom and said his hospital uses natamycin as a first-line treatment for fungal infections.

Dr Pinheiro presented at the ESCRS Virtual Winter Meeting 2022.

Rosa Pinheiro MD is on the faculty of the University of Coimbra, Portugal.

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