Contact Lenses and Dry Eyes: New Thoughts Emerge

Folks with a proper fitting pair of contact lenses would rather surrender their firstborn (okay, too harsh, make it the TV remote) than give up the convenience and crisp vision offered by their daily disposables! That means they would possibly continue wearing contacts even if they were told that it was no longer a good idea.

Eye doctors often identify contact lens wearers that have developed dry eyes, typically middle-aged females. Up until now the dry eyes were attributed to the fact that baseline maintenance tear production decreases with age and with decreased sex hormone synthesis.

Oh, forgive this digression. Did you notice I used the phrase "sex hormone" and not simply estrogen? Researchers now say the balance between androgens (present in both genders, more so in men) and estrogen (present in both genders, more so in women) is critical in moderating tear production. Both men and women develop dry eyes but more so women, possibly because of the abrupt estrogen shift that occurs in women. We know for a fact that hormone replacement therapy in eligible menopausal women can greatly relieve their dry eyes.

Back to the conflict involving dry eyes in contact lens wearers. One myth perpetuated by eye doctors is the "competing sponge" theory. Dry eye patients already make insufficient moisture for the naked eye. Introducing that thirsty soft contact lens will absorb what little water is available in the tear film to further dessicate the cornea.

Useful, new information is now available. In many patients the contact lens itself is responsible, not hormones, not sponges. The presence of the contact lens partially (or totally) numbs the surface of the cornea. Here's what happens. The delicate sensory nerves residing within the superficial cornea, (the tiny nerve fibers that sense smoke or overly chlorinated pool water), also sense very tiny changes in tear film chemistry (pH, osmolarity, etc.). These nerves automatically send the appropriate signal to the lacrimal glands: make less tears, make more tears. Loss of corneal sensation interrupts that critical tear feedback loop. Numb corneas don't send signals!

The race is on to develop contact lenses that do not anesthetize the ocular surface, thus permitting continued, comfortable wear for many folks who stand ready to surrender that TV remote.

Related Topics:

• WebMD Video: Contact Lens Comfort
• WebMD Video: UV Contacts

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