Bacterial flora of the eye and contact lenses

A modification of the bacterial flora

In France, about 4 million people wear contact lenses! 125 million worldwide!
According to a new study published in the New York journal mBio, wearing contact lenses can modify the bacterial flora naturally present on the surface of the eye. Wearers would have a large proportion of bacteria from the skin flora on the surface of their eyes.

The team of researchers followed 58 adults who wear or do not wear contact lenses for six weeks. They took 250 samples from the conjunctiva and the lenses (The conjunctiva is a transparent mucous membrane. It lines the inside of the eyelids).
This was done using a laboratory technique called "16S rRNA sequencing", which allows the identification of bacterial species. The researchers thus discovered in the carriers, a presence in great quantity of cutaneous bacteria little or not pathogenic like:

- Methylobacterium: Present in soil, dust, fresh water but are not pathogenic.
- Lactobacillus: Present in rich environments containing carbohydrate substrates such as intestinal, oral or vaginal mucosa of humans and animals. They are not pathogenic.
- Pseudomonas and Acinetobacter: They are responsible for respiratory or skin infections.
There are also, in smaller quantities, other skin bacteria such as :
- Haemophilus: responsible for otitis, sinusitis, pharyngitis, conjunctivitis.
- Staphylococcus: responsible for skin, nasal and urinary infections.

Two possible hypotheses:

For Dr. Maria Dominguez-Bello, who led this study, there are two hypotheses to explain this change in ocular microbiota:
"Either the bacteria were transferred from the finger to the lens and then to the eye, or the contact lenses exert a selective pressure on the bacterial flora of the eye. This favors the development of bacteria from the skin flora," she explains in a statement.

Contact lens wearers are at increased risk for infections that may be related to the presence of skin bacteria. However, the researchers believe that it is still too early to provide advice to contact lens wearers. In conclusion, they emphasize the importance of following good hygiene practices for the care, handling and wearing of contact lenses.

Here are some tips on how to handle your lenses with minimal risk

- Wash your hands before and after handling the lenses.
- Maintain the lens case by cleaning it with soap and rinsing it thoroughly.
- Use proper cleaning products to clean them (do not use tap water, saliva or mineral water).
- Change the product every day if you wear them every day, and every 48 hours otherwise.
- Never sleep with your lenses unless you have a prescription for them.
- Respect the wearing period! Never exceed this period: daily, bi-monthly, monthly, annually.
- Massage each lens with the product in the palm of your hand for a few seconds.
- Put the lenses in before applying makeup and take them out before removing makeup.
- Remove lenses before showering or bathing.
- Discard any damaged or dropped lenses on the outside (possible contamination).

Remove the lenses and consult an ophthalmologist promptly if you experience tearing, irritation or redness of the eye, blurred vision or increased sensitivity to light, pain, halo around lights, or a foreign body sensation.