Clinical characteristics of Acanthamoeba keratitis infections in 28 states, 2008 to 2011

The aim was to describe a geographically and clinically diverse sample of cases of Acanthamoeba keratitis (AK) and establish the risk factors for poor outcomes among patients with this disease.

We conducted a retrospective, population-based case series of 116 patients with AK identified through a national surveillance network. Data were collected via a medical record review by diagnosing ophthalmologists and by phone interviews with patients. Exact logistic regression modeling was used to determine risk factors for poor visual outcomes.

Among patients with data available on contact lens use, it was found that 93.3% wore contact lenses. The median time from symptom onset to care seeking was 2 days, whereas the median time from symptom onset to diagnosis was 27 days. Keratoplasty was performed in 27 of 81 patients with available outcome data and was more likely in patients >40 years old [odds ratio (OR) 5.25, 95% confidence interval (CI) 1.49-21.92]. When adjusted for age, the risk factors for keratoplasty included the presence of a ring infiltrate (OR 40.00, 95% CI 3.58-447.0) or any sign of stromal invasion (OR 10.48, 95% CI 2.56-55.09). One-third of patients with available data on best-corrected visual acuity had a best-corrected visual acuity <20/200, with the presence of a ring infiltrate as the only significant predictor of this outcome when adjusted for age (aOR 3.45, 95% CI 1.01-12.31).

AK remains challenging to diagnose. Consequently, patients with advanced disease are more likely to have poor outcomes, particularly if they are older. The increasing awareness of AK among general eye care providers may shorten referral times and potentially improve outcomes.