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New stabilizing agent added in corneaplasty trials
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IRVINE, Calif. - An experimental, nonsurgical method of correcting refractive errors has been modified by a new drug that could shave months off the time it takes to reshape the cornea.
Advanced Corneal Systems began developing its "corneaplasty" technique about 2 years ago. The elements necessary for the procedure include a drug that temporarily alters the molecular bonds between proteglycan molecules in the cornea - making it more malleable for a short time - and a custom-fitted, rigid gas-permeable contact lens that reshapes the cornea.
Speeding the process
Phase 1 testing on this system had been completed and phase 2 testing was underway when scientists at Advanced Corneal Systems developed a second drug that should drastically reduce the time it takes the cornea to stabilize after it has been reshaped. The contact lens used to reshape the cornea also has been redesigned, which will speed up the process as well.
"In the past, it would take sometimes a couple of weeks to get the cornea reshaped; with the new lens, we can do it in a couple of days," said Diana Schmidt, PhD, vice president of development at Advanced Corneal Systems. "Waiting for the cornea to stabilize on its own takes anywhere from 3 to 6 months. During that time, the patient has to wear a retainer lens. We're hoping that the stabilizing drop may shorten that time period to a matter of weeks rather than months."
Dr. Schmidt could not discuss how the new drug accelerated the stabilizing process because Advanced Corneal Systems is still involved in the patenting process.
Limiting noncompliance
By reducing the recovery time for patients, the stabilizing drug should limit noncompliance, which would make corneaplasty less effective.
"For patients who are very compliant and wear their lenses every night, everything's fine, but for patients who just forget or stop using their lenses, their uncorrected vision will deteriorate back to baseline," Dr. Schmidt said.
The original procedure, which did not include the stabilizing drug, had achieved good results, according to Dr. Schmidt, with most patients improving to 20/20. However, because of lack of compliance, some of the patients were unable to maintain 20/20 vision, she added.
The addition of the stabilizing drug will require Advanced Corneal Systems to repeat these tests. Testing will begin on patients with mild to moderate myopia, from -1 to -3 D and those with mild astigmatism, Dr. Schmidt said. Tests on the original procedure are still ongoing.
Advanced Corneal Systems completed phase 1 testing off-shore using the stabilizing drug during the third quarter of 1997 and will begin phase 2 testing in the third quarter of this year. By the end of the year, the company hopes to establish that the technique is safe and effective, then the company will begin large-scale clinical studies in 1999. The procedure will not be available to the public for some time, Dr. Schmidt said.
One of the advantages of this technique is that Bowman's membrane will remain intact, whereas in photorefractive keratectomy the excimer laser destroys the layer. Dr. Schmidt said that no one can be sure how important this advantage is because the long-term effects of removing Bowman's have not been determined.
For Your Information:
- Diana Schmidt, PhD, is the vice president of development for Advanced Corneal Systems, Irvine, CA 92618; (714) 788-6000; fax: (714) 788-6010; DSmdt@aol.com.