Microbial contamination of soft contact lenses & accessories in asymptomatic contact lens users

Contact lenses, especially the soft contact lenses are increasingly being used for cosmetic or therapeutic purposes. Lack of compliance and poor hygiene towards lens care is strongly associated with microbial contamination and has been proved to result in eye infections12. Microbial keratitis is one of the serious complications of contact lens use and if not treated timely, may result in permanent visual damage to the cornea. In developed countries, the incidence of contact lens associated keratitis has been increased up to 30 per cent of all keratitis cases34. The present study was planned to assess the knowledge of young medical and dental students who were using contact lens about the risk of microbial contamination associated with improper use and maintenance of contact lenses, type of microbial flora involved and their potential to cause ophthalmic infections.

Material & Methods

The study was conducted at Aacharya Vinoba Bhave Rural Hospital (AVBRH) and Jawaharlal Nehru Medical College, Sawangi (Meghe), Wardha, Maharashtra, India, during April-May 2012. Fifty medical and dental students who were asymptomatic contact lens users and who volunteered to be included in the study, were asked to fill a questionnaire containing details of lens use and six steps of lens cleaning and storing protocol. Those who followed five or more steps, three or four steps and less than three steps were classified as belonging to high, medium and low compliance groups, respectively. The study protocol was approved by the Institutional Ethics Committee and each participant gave written informed consent.

One sample each were collected from concave surface of contact lenses, lens case and tip of solution bottles with the help of sterile cotton tipped swabs that were pre- moistened with sterile brain heart infusion (BHI) broth. Sample of lens care solution was directly cultured on solid media as a drop. All samples were inoculated onto 5 per cent sheep blood agar, Mac Conkey's agar and Sabouraud's dextrose agar. The blood agar and Mac Conkey's agar were incubated at 37° C for 24-48 h, while Sabouraud's dextrose agar was incubated at 25° C and examined daily for growth of fungi and discarded at the end of three weeks. Organisms grown were identified using standard microbiological techniques5.

The data obtained were analyzed in terms of percentage contamination obtained, type of microbial flora involved and its relation with the lens care practices followed by the users using Fisher Exact test.

Results & Discussion

Thirty seven (74%) participants showed growth of organisms in at least one of the samples. Overall rate of microbial contamination among the total samples was 52 per cent (104/200). Lens case was the most contaminated sample (62%) followed by lenses (56%), tip of solution bottles (48%) and lens care solution (42%). All 104 contaminated samples grew bacteria on culture (Figure). None of the sample was positive for fungus. Pseudomonas species predominated in lenses (28%), against Staphylococcus aureus in lens cases (30%), bottles (24%) and lens care solutions (18%). Our study showed significantly higher rate of microbial contamination (P<0.05) among those who showed medium to low compliance to the lens cleaning protocol in comparison to high compliance group as shown earlier by Tuli et al6. Rates of contamination in low, medium and high compliance groups were 100, 93.75 and 43.75 per cent, respectively. Of the 50 participants, 32 were occasional users, 36 were using contact lens for >2 yr, and 18 were using for cosmetic purpose (Table).

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Fig

Microbiological profile of contaminated samples. CONS, coagulase negative Staphylococcus; NFGNB, Nil fermenter Gram-negative bacilli.

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Table Per cent distribution of contaminated samples according to the frequency, duration and reason for contact lens use

Increased rate of contamination was seen among daily users (83%) and those using lenses for purely cosmetic purposes (88%) reflecting carelessness and lack of compliance on the part of the users regarding lens care. The total rate (74%) of microbial contamination in our study was similar to the studies by Lipener et al7 (86.6%) and Emina et al8 (70.27%). Lens cases were the most frequently contaminated item (62%) followed by contact lenses as also found by others79101112.

Although Pseudomonas has been reported as the most frequent isolate from lenses and accessories3713, S. aureus was found to be the predominant isolate in our study. Yung et al9, have also found S. aureus, coagulase-negative staphylococci and Serratia species as the most common microorganisms.

In conclusion, our preliminary results showed that the lens care practices amongst the participants were not optimum resulting in high level contamination. Increased awareness among the users about the lens care practices and regular cleaning and replacements of lens cases and solutions are warranted.