Noncompliance with lens care instructions represents the primary risk factor for contact lens case contamination, according to results from a recent study.
Anastasopoulos is research operations manager, Clinical Vision Research Australia, Australian College of Optometry, Melbourne.
The time course of contamination of contact lens cases used by patients in daily wear of senofilcon-A silicone hydrogel lenses and factors predicting contamination were investigated in a large, prospective, masked study.
The study enrolled 132 subjects fitted with 2-week replacement senofilcon A contact lenses. Of the two lens care solutions used, one product was preserved with polyquaternium-1 and myristamidopropyl dimethylamine (MAPD) and the other with polyhexamethylene biguanide (PHMB). Both were used in a rinse-only regimen.
About 40 patients in each of the three follow-up groups completed the study. When they returned for follow-up, specimens from both the contact lens cases and lenses were cultured for bacteria, although the patients were not told at enrollment that cultures would be performed.
The level of contamination was graded on a 5-point scale where 0 = nil and 4 represented >300 CFU/ml. Noncompliance with various care instructions was assessed via a questionnaire and an overall noncompliance score was also calculated.
Within the group of patients who returned after 7 days, 56% of contact lens cases showed some level of bacterial contamination. However, there were no significant differences in contamination rates between follow-up groups or between the two lens care solutions at any follow-up visit.
Rates of moderate to heavy contamination were higher in the 14- and 30-day follow-up groups, but the differences compared with the 7-day follow-up group were not statistically significant, Anastasopoulos reported.