A retrospective study has revealed trends in Acanthamoeba keratitis (AK) cases in contact lens wearers in China. Although contact lens wear is not the most common risk factor for AK in China, it remains an important cause in many cases. Researchers recently found that more than two-thirds of cases were associated with orthokeratology (ortho-K) lenses. The most common risk behavior of ortho-K users was rinsing lenses, cases or both with tap water. In soft lens wearers, wearing lenses while showering or sleeping topped the list of risky behaviors.

The study reviewed the medical records of 61 cases (64 eyes) of AK related to contact lens use. A total of 32.8% of the patients wore soft lenses and 67.2% used overnight ortho-K. 

In the 20 eyes found in the early stage of AK, 13 had positive results according to Giemsa-stained smears, and 0.9% sodium chloride (NaCl) wet mounts revealed trophozoites in seven. Confocal microscopy combined with clinical signs were able to diagnoses six of these eyes. In ortho-K patients, 87.8% rinsed their lenses, cases or both with tap water. Also, 55% of soft lens wearers wore their lenses while showering.

The team also found that the rate of therapeutic keratoplasty in the ortho-K group dropped after 2005, which the researcher attribute to increasing awareness of AK by practitioners, early diagnosis and effective medical treatment. They recommend optometrists teach contact lens wearers, especially ortho-K wearers, to strictly adhere to good contact lens hygiene practices and avoid lens exposure to tap water to minimize the risk of AK. For highly suspected early-stage cases of AK, especially those characterized by epitheliopathy, they suggest 0.9% NaCl wet mounts and confocal microscopy to facilitate an early diagnosis.