A recent study sponsored by the National Eye Institute (NEI) of the optimal treatments for fungal keratitis showed that topical natamycin is still the mainstay of treatment. Adding oral voriconazole to the treatment regimen also may be beneficial to treat patients with Fusarium species.
In tropical areas, fungal infections are responsible for more than 50% of corneal ulcers and they carry a worse prognosis compared with bacterial keratitis–with higher rates of corneal perforations and the need for penetrating keratoplasty (PK), according to Jennifer Rose-Nussbaumer, MD.
With this serious clinical picture, it has been more than 50 years since a treatment for fungal keratitis was introduced. The last treatment introduced for corneal keratitis was natamycin.
While microbiology with Giemsa gram staining and culture plates continues to be the primary methods of establishing a clinical diagnosis for fungal keratitis, Dr. Rose-Nussbaumer, assistant professor of ophthalmology, Proctor Foundation, University of California, San Francisco (UCSF), considers confocal microscopy to be a fast and excellent way to diagnose filaments.
“We can diagnose the patient in the office in just a few minutes and prescribe the appropriate therapy at that time,” Dr. Rose-Nussbaumer emphasized.
She depends on anterior-segment optical coherence tomography to follow up on patients with fungal keratitis by evaluating infiltrates, scar sizes, and corneal thinning over time.
Regarding the rationale the use of natamycin for treating fungal ulcers, Dr. Rose-Nussbaumer cited the results of the Mycotic Ulcer Treatment Trial, which was a randomized, double-masked, non-placebo-controlled collaborative study (JAMA Ophthalmol 2013; 131:422-9) between UCSF and the NEI and N. Venkatesh Prajna, MD, Aravind Eye Hospital, Madurai, India.
In this study, smear-positive fungal ulcers were randomized to treatment with either topical natamycin or topical voriconazole. The primary outcome measure was the best spectacle-corrected visual acuity (BSCVA) at 3 months after the start of treatment.
The results indicated that in the 323 patients enrolled at the Aravind Eye Hospital, the eyes treated with natamycin improved more than those treated with voriconazole in the BSCVA (P = 0.006), the 6-day microbiologic cure rate (P <0.001), the infiltrate and scar size (P = 0.05), and the corneal perforation rate (P = 0.009).
“These results were especially applicable to patients with Fusarium ulcers who had a mean improvement of 4 lines of visual acuity in the group that was randomized to treatment with natamycin,” Dr. Rose-Nussbaumer reported.