Risk factors for Acanthamoeba keratitis in overnight orthokeratology lens wearers: a case-control study

The global increase in overnight orthokeratology (ortho-k) lens use for myopia control among children and adolescents has been accompanied by a concerning rise in Acanthamoeba keratitis (AK), a rare but sight-threatening complication. Modifiable behavioral risk factors in this population remain insufficiently characterized. This study aimed to identify and quantify key modifiable behavioral risk factors for AK among ortho-k lens wearers.

A case-control study was conducted. Cases were ortho-k lens wearers diagnosed with AK between January 1, 2021, and November 19, 2025. Controls were active ortho-k lens wearers with no history of AK, matched by age and sex at a variable ratio of 1:1 to 1:5, and recruited between April 15, 2025, and December 21, 2025. Data on demographics, lens wear history, and detailed lens care behaviors were collected using a standardized questionnaire. Univariable conditional logistic regression was used to estimate matched odds ratios (ORs) and 95% confidence intervals (CIs) and to identify risk factors.

A total of 79 participants were analyzed (median age, 13.0-14.0 years; 68.3% female), including 20 AK cases and 59 matched controls. Inadequate hand hygiene was associated with the highest risk (OR, 26.46; 95% CI, 3.29-212.79; p < 0.001). Adding solution to the lens case without discarding the old solution (topping off) was strongly associated with AK (OR, 17.40; 95% CI, 2.03-149.34; p < 0.001). Lens-related discomfort (OR, 14.52; 95% CI, 1.64-128.12; p = 0.004) and delayed lens case replacement (OR, 13.04; 95% CI, 1.49-114.00; p = 0.005) were also significant. Cleaning lenses with tap water was associated with a 9-fold increased risk (OR, 9.09; 95% CI, 0.97-85.61; p = 0.028). Omitting the rubbing step during lens cleaning and self-handling without parental supervision were observed exclusively in cases (OR undefined). Additional significant factors included eye discomfort during wear, showering while experiencing discomfort, and irregular follow-up visits (all p < 0.05).

Multiple modifiable hygiene and lens care behaviors are strongly associated with AK among pediatric and adolescent ortho-k lens wearers. Prevention strategies should emphasize strict adherence to proper hand hygiene, avoidance of tap water, mandatory rubbing during cleaning procedures, avoidance of topping off the care solution, timely lens case replacement, and prompt professional evaluation for ocular discomfort.