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Post-LASIK topography-driven customized ablation is promising, but not yet perfect
A realistic analysis of results shows that improvements are no more than 60%.
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ALGARVE, Portugal — Topography-driven customized ablation is a promising procedure and a definite step forward in the correction of post-laser in situ keratomileusis (LASIK) decentration. However, the technique is still far from perfect and the results are not satisfactory in all cases. This is according to Klaus N. Ditzen, MD, who spoke at the meeting of the European Society of Cataract and Refractive Surgeons here.
“From my experience, I’ve seen that this procedure works in about 60% of cases. I am still enthusiastic about it, and believe that it can be improved to give us good results up to 100%. At the present time, however, we can’t deny that there also are failures and problems,” Dr. Ditzen said.
Dr. Ditzen performs the TOSCA (topography supported customized ablation) procedure with the MEL 70 (Asclepion-Meditec AG, Jena, Germany) flying spot laser in combination with the C-Scan (Technomed Technology, San Clemente, Calif.) and Tomey TMS-3 Auto- Topographer (Tomey Corp., Waltham, Mass.) system. So far, he has treated 13 cases of post-LASIK decentration.
In five eyes, the primary treatment was carried out for myopia and in eight eyes for hyperopia. LASIK was performed with the Bausch & Lomb Surgical (Claremont, Calif.) Automated Corneal Shaper system. Flap diameter was 8.5 mm and flap thickness was 160 µm. Primary ablation was performed with the 193 nm MEL 70 with a new 1.8-mm Gaussian spot scanning system at 35 to 50 Hz.
Patients had decentered ablation from the previous procedure, or irregular astigmatism. Some had monocular diplopia or complained of glare and halos due to small optical zones.
Results
After TOSCA ablation, monocular diplopia disappeared in all cases. In seven eyes (53%), the optical zones were enlarged but the overall effects of the procedure on the quality of vision were not completely satisfying. In many cases, patients complained of blurring and color effects. In eight eyes (60%), there was a gain of one or two lines, but in the remaining five eyes (40%), there was a loss of two or more lines. Some degree of irregular astigmatism was reported in most eyes.
“The system is not as good as we would like it to be. We need more precise and sophisticated software to guide the ablation in connection with the topography and a better tracking system for the eye,” Dr. Ditzen said. “The centration of the pupil in the topography must correspond to the centration of the excimer laser at all times of the ablation. This is the principal difficulty, and the weak point, of the technique because eyes tend to move, and you get a different picture of them every 10 seconds. The problem is only partially overcome by fixing the eye with the suction ring and this, of course, renders the duration of the procedure crucial. Finally, although small decentrations can be resolved with a reasonable percentage of success, larger decentrations are difficult to deal with.”
Dr. Ditzen believes that an intensive collaboration between excimer laser and topography system manufacturers is “absolutely necessary.” He also is convinced that a wider survey on the results of the procedure is important in order to give a more objective evaluation of the technique and to ascertain its strengths and weaknesses.
“There is one aim I am sure we should pursue,” he said. “We need to be able to take intraoperative topographies, thus establishing a dynamic link between topography and laser ablation. This would be the real accomplishment of the technique.”
For Your Information:
- Klaus N. Ditzen, MD, can be reached at Bismarckstrasse 4, 69469, Weinheim, Germany; (49) 6201-12026; fax: (49) 6201-183610; e-mail: kditzen@aol.com. Dr. Ditzen has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Asclepion-Meditec AG can be reached at Prüssingstrasse 41, D-07745, Jena, Germany; (49) 3641-653332; fax: (49) 3641-653026.
- Bausch & Lomb Surgical can be reached at 555 W. Arrow Highway, Claremont, CA 91711; (800) 423-1871; fax: (909) 399-1525.
- Technomed Technology can be reached at 944 Calle Amnecer, Ste. D, San Clemente, CA 92673; (949) 366-9964; fax: (949) 366-9938.
- Tomey Corporation can be reached at 300 Second Ave., Waltham, MA 02451; (800) 358-6639; fax: (781) 290-5885.