Contact Lenses & Birth Control Pills

Does anyone know what the correlation between taking birth control pills and the possible inability to wear contact lenses is?  Wonder why difficulty wearing contact lenses would be a side effect?

The packaging states the warnings/side effects - but doesn't explain Why the pills may affect vision:
"If you wear contact lenses and notice a change in vision or an inability to wear your lenses, contact your healthcare provider.

Contact lens wearers who develop visual changes or changes in lens tolerance should be assessed by an ophthalmologist.

Most side effects of the pill are not serious. The most common are...difficulty wearing contact lenses. These side effects, may decrease or subside within the first three months of use."

[John C Hagan III, MD, FACS, FAAO]

Wearing contact lens and taking birth control pills is not the problem it used to be. This is both because the contact lens are better and the dosages of hormones smaller. It use to be a big problem with hard plastic contacts less so with gas permeable contacts and least of a problem with soft contact lens. Similar problems can occur with pregnancy, menarche and menopause.

The mechanism can be one of several ways: the eye tissue may dry making it more sensitive and cutting down wearing time, the cornea may retain fluid and change shape which may cause fitting, feeling and visual problems.

JCH III MD Eye MD