Soft Contact Lens Case Water Contamination Common

Contact lenses set with pair of contact lenses and container
Contact lenses set with pair of contact lenses, bottle with solution and container. Selective focus, shallow depth of field
Researchers asked patients to self-report hygiene for lenses, hands, storage cases, among other measurements.

Patients who wear soft contact lenses often engage in activities that result in their contact lenses coming into contact with water, which is linked with higher case contamination, according to a study published in Optometry and Vision Science.

The investigators sought to update the body of research on the microbial bioburden that water contact with contact lens presents for storage cases, which can contaminate the contact lens and ultimately raise the risk of lens-related adverse events.

Data for the study was derived from a clinical trial held in 2017 and 2018 of adult patients (N=165, mean age 28 years, 65% women) who wore regular replacement (1-, 3-, or 6-month schedule) soft contact lens daily (129 1-monthly soft lens, 27 6-monthly soft lens).

The patients described contact lens-related hygiene habits and water exposure during contact lens wear in a survey that produced a composite lens self-reported hygiene compliance score. The score evaluated the level of lens disinfection, hand hygiene, storage case hygiene, and storage case replacement schedule. They reported the amount of water exposure, demographics, and contact lens and disinfection system types. The researchers performed microbial analysis of the storage cases.

Most patients reported they had moderate (n=78) or poor (n=58) hygiene compliance. About 25% of patients reported incidental sleeping overnight with contact lens still applied, and nearly half (n=75) reported showering while wearing contact lenses and swimming (n=82, 53 without goggles) while wearing contact lenses in the past year. Overall, 81 participants had good and 84 had poor water contact behavior.

Average contact lens case bioburden was 3.10 log CFU/ml and median endotoxin contamination was 1.37 EU/ml. Sixty-one storage cases had up to 2 EU/ml, and 65 had more than EU/ml. Sixty-five cases had high endotoxin levels.

Endotoxin levels in contact lens storage cases were linked with bacterial bioburden levels (P <.001).

In multivariate analysis, researchers found that wearing contact lenses for more than 5 years (P =.007), using 6-month replacement frequency lenses (P =.05), napping while wearing lenses (P =.004), not rinsing storage cases after use (P =.02) and waiting at least 3 months to replace storage cases (P =.03) was linked with storage-case bioburden.

Women’s lens cases had twice the odds of having high endotoxin levels (P =.02 OR 2.54), according to the report. Purchasing lenses online rather than from a practitioner (P =.03; OR, 2.31), using storage cases for more than 1 month, and handling lenses with wet hands (P =.01 OR 2.41) were linked with high endotoxin levels (P <.02; OR, 2.48).

Showering (P =.001) was linked with higher overall storage case bioburden.

The researchers found that overall water exposure score had an ordered correlation with contact lens storage case bioburden (Spearman R=0.197; P =.01).

The researchers recommended optometrists educate patients, including those who have worn lenses for years, about the risks of noncompliance with lens care and hygiene.

Limitations of the study included a convenience sample population and lack of measurement of refractive error and motivation for contact lens wear.

Disclosure: This research was supported by Alcon Foundation. Please see the original reference for a full list of disclosures.


Arshad M, Carnt N, Tan J, Stapleton F. Effect of water exposure on contact lens storage case contamination in soft lens wearers. Optom Vis Sci. 2021;98(9):1002-1010. doi:10.1097/OPX.0000000000001772