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Beware: Contact Lenses Change Eye Bacteria For The Worst

Beware: Wearing  contact lenses change the eye’s bacterial populations for the worst, says a new study published in mBio®, an online open-access journal of the American Society for Microbiology. This might explain why lens-wearers are more prone to infections.


The human body generally contains more bacterial cells than its own. This intimate coexistence is based on the mutual benefits entailed in the interactions. In short, humans need these microorganisms that occur naturally in different proportions and of different species in regions of their bodies to function properly. The balance that constitutes the correct number of bacteria and species thereof can, however, be disrupted, and the consequences will thereafter follow. A new study shows how contact lenses can change the composition of the microbial community of the eyes, thereby potentially causing infections.

Contact lenses modify the eye microbiome such that the latter becomes more comparable to the skin bacterial community. By inserting contact lenses, a certain amount of skin bacteria are thus introduced into the eye.

The bacterial populations of the eye (more specifically, in the conjunctiva) and the skin beneath the eye were compared in 58 adults (lens-wearers and non-wearers). The results show a greater variety of bacteria on the ocular surface than on the skin or on the contact lenses. This was how it was found out that the microorganisms from the ocular surface of people wearing lenses were more skin-like (bacteria Pseudomonas, Acinetobacter, Methylobacterium, and Lactobacillus were found in greater proportions) as opposed to those people not wearing lenses. On the other hand, non-lens wearers had a greater abundance of these bacteria in their skin samples than in their eye.

Furthermore, bacteria Haemophilus, Streptococcus, Staphylococcus, and Corynebacterium were in lower proportions in the eyes of lens-wearers as compared to non-lens wearers. The conjunctiva of non-contact-lens-wearers were more rich in bacteria Haemophilus, Neisseria, Streptococcus, Staphylococcus, Rothia, and Corynebacterium, marked with a lower abundance of Pseudomonas, Acinetobacter, Sphingobium, and Methylobacterium.

How do the skin bacteria get into the eye through the lenses? Senior study author Maria Dominguez-Bello suggests that the transfer might happen from the fingers to the lens, and then to the eyes. Or, what is also possible is that the lenses cause skin bacteria to thrive more than the eye microorganisms, constituting an example of selective pressure.

As has been mentioned previously, the balance of the different types of bacteria in the different regions of the body’s internal environment serves a purpose. For instance, the bacteria in the skin protect the skin from being infected by harmful bacteria, among other benefits they confer. So, Dominguez-Bello points out how contact lenses have been mentioned to be a risk factor for eye infections — their findings might shed light on cases entailing greater risk of developing eye infections in those individuals who wear contact lenses.

The findings are, however, not conclusive enough to recommend anything based on them to lens-wearers.


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