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Custom ablation studies have shown excellent results
The Visx C-CAP Method and TOSCA/WASCA have shown excellent responses for custom ablation.
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BOSTON — While companies are touting custom ablations as something coming soon to the United States with the introduction of wavefront technology, in reality the procedure has been happening with fairly good success around the world.
The Visx Custom Contoured Ablation Pattern (C-CAP) and Topography Supported Customized Ablation (TOSCA) have been used extensively over the past 2 years to make enhancements to patients who have had laser in situ keratomileusis (LASIK) who have not responded as planned to the procedure.
The results of these custom ablation procedures were presented at the annual meeting of the American Society of Cataract and Refractive Surgery.
Sheldon Herzig, MD, started using the C-CAP system to correct corneal irregularities 1 year ago and has performed 25 procedures with this system. It was designed to eliminate corneal irregularities that affect best corrected visual acuity (BCVA) and quality of vision.
Dr. Herzig pointed out that his experience with the system has been for previous refractive surgery problems and some post-keratoplasty irregularities. While he has not performed enhancements for keratoconus, he pointed to the success of some significant studies using the system in Brazil to correct keratoconus with photorefractive keratectomy.
The CAP system extends a beam of variable thickness between 1.2 to 6.5 mm onto the cornea using a Cartesian X/Y system and maps the eye and plots an ablation plan.
He explained that for decentered ablations he calculates the necessary ablation depth by placing the topography cursor over the undercorrected area to measure its elevation and adds this to the approximate depth that should have been achieved in this area. Dr. Herzig will typically go to another section of the eye where the ablation was made correctly and use that as a reference.
Always an enhancement
Dr. Herzig presented several cases to explain his procedure. The first patient presented was a 49-year-old male 20 years postop for keratoplasty to fix keratoconus. He had a great deal of irregular astigmatism and BCVA of 20/60, some corneal thinning and posterior elevation.
Dr. Herzig did not attempt to treat his refractive error. The goal of the CAP LASIK was to eliminate the large eccentric elevation causing the irregular astigmatism. “Postop the patient’s astigmatism was more regular with BCVA of 20/40, and he was able to read comfortably because of residual myopia,” Dr. Herzig said.
The second patient he presented was a 29-year-old woman who had received a –8.00 D decentered ablation and was unhappy with night glare. Dr. Herzig treated her undercorrected area with three overlapping spheres of diameter of 2.5 mm and varying depth of 22 to 27 µm.
Postop, her glare systems were gone, but she had increased astigmatism and myopia because of peripheral flattening. “These patients should be warned that they’ll probably need a second treatment to adjust for refractive error that is unpredictable before you start,” Dr. Herzig said.
He said to expect relative central steepening when doing peripheral flattening, which will increase the patient’s myopia.
“My CAP treatments have not all been perfect. We’re limited by the information that we get from the corneal mapping system, which has its own inherent inaccuracies. I think that CAP is useful for treating gross irregularities. Fine irregularities that are symptomatic will require more advanced technology such as wavefront,” Dr. Herzig said.
He went on to explain that CAP is likely a bridge to future technologies to treat patients that are “intolerable of their symptoms today and simply can’t wait for wavefront.”
Subjective evaluations the key
Frank J. Goes, MD, showed his results using TOSCA, the MEL 70 Asclepion Meditec (Jena, Germany) Laser and the Tomey (Waltham, Mass.) TMS 3. He stated that he had been using the MEL 70 for 2 years in Antwerp, Belgium, for customized ablation using topography.
TOSCA is a workstation linked to an excimer laser that utilizes topography for a custom profile and an active eye tracker. Surgeons can use a suggested program or modify the program and it will show you how much cornea will be ablated and where.
While the TOSCA results did show that visual acuity improved, the true mark of success was that the subjective complaints improved, as well.
The indications for using TOSCA included decentered ablations, 48%, small optical zones, 20%, ghost and glaring and corneal irregularities. He said he had performed 45 cases, with 8-month follow-up, and 23 patients had follow-up of more than 1 year.
The BCVA improved in six, remained unchanged in 35, and decreased in one eye. The uncorrected visual acuity improved in five, was unchanged in 28, and only one eye had a loss. When it came to the subjective evaluation, 62% improved dramatically, 13% improved slightly, 20% were unchanged and 5% decreased.
“We’re using this treatment as an enhancement procedure. The ultimate goal is to give our patients the vision greater than or equal to the vision we can give with a contact lens,” Dr. Goes said.
Wavefront Supported Customized Ablation (WASCA) will be the next stage of customized ablation, he said. Dr. Goes added that it is in development, and the clinical trials have shown remarkable results. He does not believe TOSCA will become obsolete because “currently the wavefront-guided lasers are only good for dealing with higher-order aberrations and not yet ready for important decentrations and important aberrations.”
For Your Information:
- Sheldon Herzig, MD, can be reached at Herzig Eye Institute, The Colonade, 131 Bloor St. W, Ste. 210, Toronto, Ontario M55 IRI, Canada; (416) 929-2020; fax: (416) 929-0232. Dr. Herzig has no direct financial interest in any of the products mentioned in this article. He is a paid consultant for Visx.
- Frank J. Goes, MD, can be reached at Willem Klooslaan 6, Antwerp, 2050, Belgium; (32) 2-219-3925; fax: (32) 3-219-6667; e-mail: frankgoes@village.uunet.be. Dr. Goes has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Visx Inc. can be reached at 3400 Central Expressway, Santa Clara, CA 95051-0703; (800) 246-8479; fax: (408) 773-7055.