20 October 2010

Dr. Eileen Lo says, “The best contact lenses is no lenses at all”

When Polymethylmethacrylate (PMMA) lenses, known as “hard” contact lenses, were introduced to the market during early 1960s, they challenged eyeglasses which seemed to be the only corrective option for millions of people. Wearing the hard contact lenses, patients were reporting some interesting experiences. Some noted that they could see clearly for a period after they removed their contacts without the aid of glasses. They might wear their contacts all day and remove them to go to a cocktail party or such. Doctors noted that in some cases progressive myopia slowed down in people who had repeatedly year after year manifested increases in prescription. Doctors discovered that lenses that were fit flatter than the curvature of the cornea were the reason for both phenomenon, so they started purposefully fitting the contact lenses flatter. The results were dramatic in some cases. Patients with  less than a certain amount of minus power could remove lenses and see, sometimes for an entire day. The resulting therapy was later called Orthokeratology or orthoK for short.

While interesting and helpful for many patients, PMMA material is not permeable to oxygen, so there were some inherent risks in extending wear of these lenses to achieve the desired effect. Also, fitting them to achieve the desired effect was an arduous and inexact science.

In the 1970s plastics for contact lenses were developed that had a higher permeability to oxygen. The flourosilicon elastomers proved safer and healthier for the eye and reduced the risks of orthokeratology, but fitting these lenses was still challenging for doctor and time consuming for patients.

In the 1990s plastics were developed that reached a new level of oxygen permeability. These “hyper-permeable” lenses made sleeping in gas permeable contacts much safer. In the late 1990s, a company also developed a lens shape, known as “reverse geometry” that greatly increased the ease of fitting and success for orthokeratology patients.

Today, combining the healthier materials with the reverse geometry dimensions, orthokeratology is now mainstream. It provides excellent vision sans glasses or contacts for thousands of people worldwide. Studies have been performed that demonstrate the safety and efficacy of the procedure, and other studies have been performed that demonstrate that orthokeratology is successful at managing myopic shift, providing the only known way of providing myopia control for contact lens wearers.

To learn more, please make an appointment with Dr. Eileen Lo who is an experienced orthoK practitioner and receive a consult.