corneal reshaping
Corneal Reshaping: Is it Really for You and Your Patients?
OM presents both sides of the issue.

Is accelerated corneal reshaping (orthokeratology, corneal refractive therapy) an effective method of temporarily eliminating refractive error? Alan Glazier, O.D., F.A.A.O., of Rockville, Md., responds to various health and practice management counterpoints related to this method of vision correction.

COUNTERPOINT: In my practice, I don't currently fit patients with corneal reshaping lenses and both health and patient satisfaction issues play into my decision. I've heard about side effects presented by the reshaping contact lenses. Don't other types of contact lens materials, which provide high-oxygen transmissibility, better serve patients?

DR. GLAZIER: The most significant risk for extended contact lens wear is keratitis from Pseudomonas aeruginosa, an anaerobic bacterium that binds to contact lenses and penetrates a compromised epithelium. Increases in oxygen transmissibility have shown to decrease binding of P. aeruginosa. The same study also showed that overnight wear of high-Dk contact lenses suppressed surface epithelial shedding, leading to a corneal environment unfriendly to Pseudomonas infection.

People who wear high-Dk ortho-k lenses while they sleep benefit from oxygen when they remove their lenses and have their eyelids open, whereas people wearing other types of contact lenses deprive their corneas of oxygen when they close their lids at night and when the cornea is covered during the day.

Extended wear of high-Dk lenses followed by an entire day of oxygen exposure without lenses can help re-establish corneal integrity and reduce overall risk of epithelial penetration by P. aeruginosa.

Long-term issues

COUNTERPOINT: I have concerns for damage to the cornea and/or epithelium. Corneal reshaping lenses apply pressure for a significant period -- about eight hours each day. Over time, wouldn't this "pushing" cause permanent damage? In addition, if a patient decides that he would like to discontinue wear, doesn't it take a significant amount of time for the cornea to recover and return to its original curvature? This has significant implications, especially for those patients who would consider refractive surgery.

DR. GLAZIER: In the past, experts believed that ortho-k flattened the entire cornea, reducing myopia. Data presented at the Global Orthokeratology Symposium in July 2004 indicates the epithelium being pushed, or redirected away from the central cornea to provide the greatest flattening effect.

It has been shown that simply discontinuing lens wear can restore the original architecture of the cornea. The epithelium continually regenerates, so any damage that "pushing" may cause to the epithelial structure is reversible. One study has shown that just one night of no lens wear restored central corneal thickness. The study also found that recovery of corneal curvature was complete one week after patients discontinued lens wear.

Visual acuity

COUNTERPOINT: My goal is to provide my patients with the best possible vision correction. With corneal reshaping lenses, I understand that I can't tell my patients in advance how their vision will improve. They must wait, sometimes weeks, to experience and understand the benefits of these lenses. Promoters of corneal reshaping claim it's suitable for those who enjoy active lifestyles because these patients won't have to wear a mode of vision correction during sports or other activities. But I'm concerned that these patients would enjoy better vision with other modes of vision correction.

To me, these points raise patient satisfaction issues. Considering that other options that provide patients with immediate vision correction are available, how satisfied will my patients be in corneal reshaping lenses?

DR. GLAZIER: Looking through an external refractive element can degrade quality of vision. Physical issues related to having a piece of plastic in the eye are common during daytime contact lens wear, even in high-Dk lenses.

One study evaluated patients' perceptions of visual quality of life differences by having subjects wear overnight corneal reshaping lenses or daily wear soft lenses for eight weeks, then answer a questionnaire. The subjects then wore the alternate mode for eight weeks and again answered the questionnaire. Of 45 subjects completing the study, 32 chose to continue with the corneal reshaping lenses and 13 chose to stay with the soft lenses, a 71% preference for overnight ortho-k.

COUNTERPOINT: When my patients experience problems associated with traditional contact lens wear (e.g., corneal ulcers), I can tell them to discontinue wear for a few days and rely on their glasses. With corneal reshaping lenses, I'm concerned that such breaks in lens wear would interfere with the patient's visual acuity as the cornea would revert back to its original shape.

DR. GLAZIER: It's not the contact lens that causes the corneal ulcer, but the anaerobic environment brought on, limiting the amount of oxygen that reaches the cornea. The paradigm has shifted; the advent of high-Dk materials combined with allowing atmospheric oxygen to reach the cornea is preferable to the antiquated method of having patient's remove lenses for a few days, take breaks to wear glasses and for you to recommend they not sleep in their lenses. It's in the best interest of many of our patients' corneal health, comfort and vision to provide ortho-k as an option.

Dr. Glazier runs a private practice outside of Washington, D.C. and owns an ophthalmic research and development corporation focusing on presbyopic solutions.