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Intrastromal devices expand options in keratoconus patients, surgeon says
In clinical studies, Intacs, Ferrara Rings and intralamellar grafts show promise as new treatments for keratoconus.
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ANAHEIM, Calif. — Additive refractive surgical procedures — those that add material to the cornea instead of removing tissue — can be off-label options for treating severely progressive keratoconus, according to a speaker here.
“Intralamellar corneal devices and grafts are an exciting new option aimed at restoring corneal thickness and vision in keratoconus patients,” David J. Schanzlin, MD, said at the American Academy of Ophthalmology meeting. Dr. Schanzlin was the recipient of the Barraquer Award, and he delivered the Barraquer Lecture at a symposium on presbyopic correction.
In the United States, 5,000 corneal transplants are performed each year for contact-lens-intolerant keratoconus, Dr. Schanzlin said. Astigmatism persists in many of these patients, and the rate of keratoconus progression is high (17.9%).
While intralamellar additive procedures have not been proven to stop progression of keratoconus, they can improve vision significantly for these patients, he said.
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| (Images courtesy of David J. Schanzlin, MD.) | |
Intacs
Intrastromal rings and ring segments include Intacs (Addition Technology) and Ferrara Rings (Mediphacos). These devices have been used to correct astigmatism, reduce myopia and produce good visual results in keratoconus patients, Dr. Schanzlin said.
Intacs have been implanted in more than 166 keratoconic eyes worldwide, Dr. Schanzlin said. “Outcomes have been exceptional,” he said. “The improvement in best-corrected visual acuity is statistically significant in all studies.” In the United States, use of Intacs for keratoconus is not approved by the Food and Drug Administration.
In combined North American and European studies, 79% of patients gained two or more lines of vision after Intacs treatment, Dr. Schanzlin said. Results from the European Keratoconus Study revealed that 22% of patients achieved 20/30 vision after Intacs surgery, and 48% of patients achieved 20/40 vision.
Dr. Schanzlin noted that the location, orientation and size of the PMMA intrastromal segments do not predict an outcome of success. “Various sizes and orientations of arcs were used in the studies, and the success rates were still similar,” Dr. Schanzlin said.
Future technology may enable surgeons to customize segments to each patient’s refractive need, Dr. Schanzlin added.
“We may soon be able to specify the arc length, diameter and vary the thickness along the arc in order to suit our patients’ needs,” he said.
Ferrara Rings
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Ferrara corneal rings have also shown effectiveness for keratoconus in clinical studies, Dr. Schanzlin said.
Developed by Brazilian ophthalmologist Paulo Ferrara, MD, the rings are used throughout Europe and South America to treat keratoconus.
“The Ferrara Ring has a similar diameter to Intacs at 7 mm, which can achieve an even greater myopic correction,” Dr. Schanzlin said.
In a recent study carried out by Dr. Ferrara, researchers implanted 26 keratoconic eyes with the Ferrara Ring. Results were positive, with patients experiencing “even more myopic effect than with Intacs,” Dr. Schanzlin said.
“In some cases, patients got up to 10 D of correction,” he noted.
A similar study by Dr. Ferrara, published in the Journal of Refractive Surgery, found that the refraction of 36 eyes improved from an average of –7.29 ± 3.12 D to –4.80 ± 3.04 D 12 months after implantation.
Uncorrected visual acuity improved in 28 eyes (78%) and best-corrected visual acuity improved in 29 eyes (81%), according to the study.
While results for PMMA rings and inserts for keratoconus are promising, Dr. Schanzlin stressed that they are not a cure for the disease. “We have no evidence that inserts will stop disease progression, but they may slow progression,” he noted.
Dr. Schanzlin added that patients may benefit from contact lens wear or glasses after surgery to improve their vision.
Donor inserts
Dr. Schanzlin also discussed another promising treatment for keratoconus, intralamellar donor inserts.
In an early clinical study, Dr. Schanzlin said that surgeons implanted nine keratoconus patients with 7.5-mm donor buttons. The corneal graft was treated with an excimer laser for refractive adjustment, and a flap was sutured over the dome, Dr. Schanzlin said.
“Results were very promising,” he said. “Uncorrected visual acuity was better than preop visual acuity in these eyes.”
In the near future, surgeons may be able to customize these donor implants to suit patients’ corneal dimensions and refractive needs, he noted.
“Surgeons will cut buttons in various fashions with femtosecond lasers so that grafts will be customized to patients’ measurements,” Dr. Schanzlin explained. “Implantation is then made in a large lamellar pocket.”
For Your Information:
- David J. Schanzlin, MD, can be reached at the UCSD Shiley Eye Center, 9415 Campus Point Drive, La Jolla, CA 92093; 877-921-3937; e-mail: schanzlin@cornea.ucsd.edu. Dr. Schanzlin has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Addition Technology Inc., manufacturer of Intacs prescription inserts, can be reached at 155 Moffett Park Drive, Suite B-1, Sunnyvale, CA 94089; 408-541-2700; fax: 408-541-1400; e-mail: intacs@additiontechinc.com; Web site: www.getintacs.com.
- Mediphacos Ltda., manufacturer of the Ferrara Ring, can be reached at Rua Mestre Luiz, 31, Belo Horizonte, MG, 30330-070, Brazil; 800-31-1111; fax: 31-3225-8648; Web sites: mediphacos.com.br or www.ferrararing.com.br.
Reference:
- Miranda D, Sartori M, Francesconi C, Allemann N, Ferrara P, Campos M. Ferrara intrastromal corneal ring segments for severe keratoconus. J Refract Surg. November-December 2003;19(6):645-53.