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DISCUSSION
Estimation suggests that there are approximately 125 million contact lens wearers worldwide where the United States alone may have as many as 38 million contact lens wearers [9, 10]. With millions of individuals wearing contact lenses, even a small percentage of complications create a major public health problem [24].
Our study population forms a majority of female students which are gendercomparable to other studies in this age group [9, 11, 12]. The median duration of contact lens wear among our participants was 3 years. For the current pair of lens, the mean duration was 30(2.5) days and the daily use was almost up to 10 hours.
Pritchard et al[13] found that frequent replacement of soft lenses for daily wear as compared to nonreplacement daily wearing is reported less likely to cause contact lensinduced complications and improves satisfaction with lens wearing. Besides the association of length of wear with bacterial colonization, the duration of lens wearing is also associated with other physiological alterations. Simon et al[14] reported that the severity of cytological changes increased with duration of lens wearing.
An increasing span of contact lens wearing has been associated with the morphological changes in the corneal endothelium. Contact lens wearing also caused increased corneal thinning proportional to the duration of contact lens wearing [15]. These findings indicated that with the increase of duration of lens wear and the morphological and cytological changes, wearers are susceptible to infections, especially true with the presence of pathogenic bacteria such as Pseudomonas sp.S. aureus and other gram negative bacteria. Manifestations related to contact lens wearing like dry eye, red eye, foreign body sensation or grittiness, itchiness, blurred vision and watery eyes are among common associated problems with contact lens wearing [13, 16].
We isolated 82% bacteria from the lenses and 32% from storage solutions. In majority of contact lens contamination by one type of bacteria was predominant (Figure 2). Isolation of bacterial colonies in our samples shows close similarity with previous findings [1, 58, 1620].
The most common gram positive bacteria isolated from the contact lenses is coagulase negative staphylococcus which is also a normal constituent of ocular microbiota [14, 1722]. Pseudomonas sp. and Serratia sp. are the two most common gram negative bacteria being isolated [1, 5, 6, 19]. However, these bacteria were isolated infrequently and showed a low isolation frequency.
The colonization of contact lenses with the normal ocular microbiota may indicate that the most likely source of bacteria Figure 2Number of different species of bacteria (in percentage) isolated from contact lenses and solutions
is the lid margin which was introduced during the handling of lens or during normal daily wearing, as previously suggested [18, 21, 22]. Other practices, such as rubbing or touching the area around the eyes during contact lens wearing, may also cause the colonization of bacteria on the surface of contact lenses.
Whereas the colonization by gram negative bacteria is proposed to be originated from domestic water supply [18]. These microorganisms are waterborne bacteria and occur naturally in water droplets. Another potential source of bacteria is the lens cases. Devonshire et al[2325] . Shows that cases used with conventional wearing and disposable systems were both contaminated which may lead to colonization.
Our study also showed contaminated storage solutions with coagulase negative staphylococcus predominating. There are also other bacteria isolated from storage solutions but are in a lower frequency (Figure 1). The presence of microorganisms in storage solutions raised the questions of the efficacy of these agents in disinfection properties [26, 27]. Donzis et al [26] found that 13% of commercial contact lens care solutions were contaminated. They also reported that contaminated commercial solutions were opened and used for a longer period of time than uncontaminated solutions. The contaminating bacteria are thought to have been introduced to the lens storage as a result of lens handling and subsequent failure to disinfect lenses [6, 2427].
The fact that lenses were colonized by normal ocular microbiota during uncomplicated wear supports that these bacteria could be nonpathogenic. Colonization of the lens surface with bacteria that are commensal to the eye may inhibit the adhesion of pathogenic species to the lens [1, 18, 20].
However, essential knowledge regarding contact lens and its accessories and hygienic practice when handling them are imperative to prevent undesirable adverse effects from contact lens wearing. Strict adherence to the manufacturers guidelines may reduce the rate of highly morbid complications.
ACKNOWLEDGEMENTS
The authors would like to acknowledge laboratory staff of the Medical Microbiology Department, School of Medical Sciences, University Sains Malaysia, for their assistance during the period of the study and all the undergraduate students of the Health Campus, School of Medical Sciences, University Sains Malaysia, who have participated in this study.
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