Acidification of the tear film

Raising and lowering of the pH of the tear film occurs due to the retention of carbon dioxide (hypercapnia), which is formed as a result of the application of contact lenses. This causes acidosis of the tear film, and subsequently – corneal acidosis. Today, most contact lenses (except PMMA pmma.html) have some degree of transmission, allowing the exchange of gases through the lens and prevent increasing acidification of the cornea.