Glenview, IL—Acanthamoeba keratitis might be a rare corneal disease, but its deleterious impact on vision and incapacitation of the patient cannot be over-emphasized.
The potential for severe visual loss, substantial associated pain, and lengthy period of therapy exists.
However, timely recognition, establishment of a specific diagnosis, and rapid aggressive therapy are keys to the best possible outcomes in this patient population, said Elmer Y. Tu, MD.
Delayed recognition is the most common controllable factor leading to a poor outcome, said Dr. Tu, professor of clinical ophthalmology, University of Illinois Eye and Ear Infirmary, Glenview, IL.
Recognition often is delayed, Dr. Tu pointed out, because Acanthamoeba is rarely acute, but rather presents as a subacute or chronic parasitic infection that primarily affects the cornea, mimicking closely the presentation of noninfectious disorders, such as dry eye and non-specific epithelipathies, or other subacute infections like fungi, microsporidia, and herpes.
“Most patients are treated first for other diagnoses, which delays recognition and appropriate treatment for weeks or even months,” Dr. Tu said. “It is critical that physicians understand the risk factors associated with Acanthamoeba keratitis, because it can look like anything else.”
Importantly, most cases of Acanthamoeba keratitis develop in patients who wear contact lenses, with the incidence rates the same between hard and soft lenses, and 7% to 11% of patients can have bilateral disease.
Interestingly, the risk of development of Acanthamoeba keratitis in the United States has increased significantly over the past 10 years.
“The reason that recognition is so important was demonstrated in our 2007 study in which the main prognostic factor that determines the visual outcome is the anatomic level of the disease,” Dr. Tu said.
He and his colleagues reported in Ophthalmology (2008;115:1998-2003) that the disease stage at presentation in our first 65 patients was 10 times more likely to have a worse visual outcome if the presence of Acanthamoeba went unrecognized in its early stages.
The prognosis is guarded in the presence of deep stromal keratitis, ring infiltrates, and extracorneal inflammation. In contrast, the prognosis is good when findings are restricted to epitheliitis, or anterior stromal disease with or without radial neuritis.