From the uninfected eye one may consistently demonstrate a bacterial flora that is considered to be "normal."1 Cultures from the lids and conjunctivae usually reveal Staphylococcus albus, often accompanied by corynebacteria, termed "diphtheroids." S aureus is less frequently encountered, though it is by no means uncommon. Other microorganisms are occasionally found. The same organisms are found on the skin with a frequency approximating that obtained in eye cultures, and the skin flora is the usual source of the eye flora.
The fact that there are several million wearers of contact lenses suggests that lenses cause little or no deleterious alteration of the bacterial flora of the eye. The lens case, often a closed container retaining moisture and material deposited on the lens when placed in the case, may provide a favorable environment for bacterial growth.2 A lens from such a case may introduce organisms onto the corneal surface
WINKLER CH, DIXON JM. Bacteriology of the EyeIII. A. Effect of Contact Lenses on the Normal Flora. B. Flora of the Contact Lens Case.. Arch Ophthalmol. 1964;72(6):817-819. doi:10.1001/archopht.1964.00970020819016