Sight-threatening keratitis seen in orthokeratology patient

"Orthokeratology is a nonsurgical treatment in which rigid gas permeable contact lenses are used to flatten the cornea and reduce myopia. Overnight wear of the lenses is required, and infection is a potentially sight-threatening complication," Dr. Sebrow said. "Acanthamoeba is becoming recognized as an important differential in keratitis occurring in patients being treated with orthokeratology."

The patient was a girl, aged 14 years, who noticed redness in her right eye while on a camping trip. She was examined by her optometrist, who had been treating her with overnight orthokeratology for about 1 year and was referred to a local ophthalmologist who treated her with steroids and trifluridine (Viroptic, Monarch Pharmaceuticals Inc.) for herpes simplex virus keratitis. The patient then was referred to Dr. Sebrow with persistent ocular redness and epithelial defect after being treated for 4 weeks.

"The differential diagnosis included herpes simplex, Acanthamoeba, fungus, and a nonhealing epithelial defect," he said. Because the cultures were negative, Dr. Sebrow treated the nonhealing epithelial defect with topical fluoroquinolone, steroids, and lubricants. As a result of this treatment, the epithelial defect closed. By Sept. 6, 2004, however, the epithelial defect was 5 × 5 mm, and a corneal biopsy was planned, he said.

Therapeutic PK

The management plan changed because of rapid progression of the infiltrate to within 1 mm of the limbus with the presence of hypopyon. On Sept. 14, 2004, Dr. Sebrow performed a therapeutic penetrating keratoplasty (PK).

"The host button pathology revealed the presence of Acanthamoeba trophozoites in the stroma," he reported.

After the surgery, the patient received prophylaxis that consisted of chlorhexidine 0.02% (Betasept, Purdue Frederick) eight times daily and itraconazole (Sporanox, Janssen Pharmaceuticals) 200 mg twice daily. Two weeks after the surgery, the Acanthamoeba recurred in the graft. Polyhexamethylene biguanide (PHMB) 0.02% eight times daily (Baquacil, Avecia Ltd.) was added to the treatment regimen.

The patient was culture-negative in November 2004, and her treatment was tapered to facilitate re-epithelization, according to Dr. Sebrow. "However, the graft developed opacification and neovascularization over the course of the treatment. In July 2005, we performed a second penetrating keratoplasty. The patient's visual acuity is now 20/25 corrected, and there has not been another recurrence of the Acanthamoeba," he said.

"The incidence of Acanthamoeba in contact lens wearers, based on the literature, is about one case of Acanthamoeba per 30,000 wearers of hydrogel lenses and one case per 300,000 wearers of gas permeable lenses," Dr. Sebrow continued.