A large proportion of the respondents reported some behaviours considered risk factors for infection. Specifically, 43% reported using their lenses longer than recommended, 41% reported occasionally showering while wearing the lenses, 32% did not change the solution in the cases daily, 29% did not clean the lens cases, 22% sometimes rinsed the lenses with tap water and 21% sometimes failed to wash their hands before handling their lenses.
The real-time PCR detected the DNA of Acanthamoeba in 87 of the 177 samples (49%). There was no significant difference in the contamination of contact lenses between male and female participants. Nor was there a statistically significant difference according to the hygiene habits of the users.
Of those who reported failure to clean their lens cases, 61% had contamination with Acanthamoeba versus 29% of those who cleaned their cases. This correlation approached statistical significance (P = 0.062).
The researchers also performed a real-time PCR to detect the two most common species associated with microbial keratitis, P. aeruginosa and S. aureus. They did not find any statistically significant association between the presence of these organisms and hygiene habits, but they found that Acanthamoeba was more likely to be present in the absence of P. aeruginosa.
The researchers also cultured contact lenses and their solutions on non-nutrient agar plates seeded with inactivated E. coli. They were only able to cultivate amoeba on one sample (0.6% of the total samples.)
The owner of this contact lens was a female who reported wearing her contact lenses longer than recommended, not washing her hands before handling her contact lenses, and sometimes rinsing her contact lenses with tap water or showering while wearing them. She also said she felt some eye discomfort, a possible indication of the presence of an organism such as Acanthamoeba, bacteria or fungi.
Among all the participants, the researchers didn't find any statistically significant correlation between eye discomfort and any of the hygiene habits. Once again, not washing contact lens cases came the closest; of the 49 people who failed to wash their cases, 31 (63.3%) had eye discomfort. And of those, 20 (64.5%) had Acanthamoeba DNA on their lenses (P = 0.073).