Better outcomes seen with addition of iris registration

Alexandria, Egypt-Patients with mixed astigmatism are considered a challenge for corneal refractive surgery because of the configuration of the bitoric ablation platform. These patients, when treated with wavefront-guided LASIK using a specific platform (CustomVue, Advanced Medical Optics [AMO]), achieved good visual outcomes that are safe and predictable, according to Mounir A. Khalifa, MD, professor of ophthalmology, Tanta University, Alexandria, Egypt.

"In bitoric ablations, centration and the torsional alignment are crucial to the outcome. Because of this, we evaluated the value of iris registration technology in the treatment of these patients," explained Dr. Khalifa, with a private practice in Alexandria, Egypt.

The patients were followed for 3 months. "The safety, efficacy, and predictability of both groups were very satisfactory, but in the group treated with iris registration technology, there was greater improvement in the visual outcomes; however, the differences did not reach significance," Dr. Khalifa reported.

When the investigators analyzed the patient data, they found a significant increase in the total higher-order root mean square in the group not treated with iris registration technology from preoperatively to postoperatively. Also, a significant difference between the postoperative data in both groups was observed. No significant change in coma or spherical aberration was seen between the preoperative and postoperative data in each group. Neither was a significant difference noted between both groups either preoperatively or postoperatively. A significant difference in trefoil was seen postoperatively between the two groups, Dr. Khalifa reported.

Secondary astigmatism

Dr. Khalifa underscored, however, that they found a very significant increase in secondary astigmatism between the preoperative and postoperative results in the group not treated with iris registration technology. A significant difference was noted between the two study groups, with the higher incidence of secondary astigmatism in the group not treated with iris registration technology.

Dr. Khalifa presented one case report from each of the study groups. In the group not treated with iris registration technology, an increase in the postoperative trefoil and the postoperative coma was seen, as was increased secondary astigmatism in both directions. The patient treated with iris registration technology, however, showed no change in trefoil or secondary astigmatism preoperatively to postoperatively.

"Wavefront-guided LASIK is safe, effective, and predictable in patients with mixed astigmatism, with or without iris registration technology. Many patients gained one or more lines in best-corrected visual acuity in both groups. Scotopic contrast sensitivity significantly improved in both groups; however, the group treated with iris registration technology had a more significant improvement," Dr. Khalifa said.

"Trefoil and secondary astigmatism showed the most significant improvement with iris registration technology, indicating more accurate axial alignment by the pupil centroid shift and more accurate radial alignment by the automatic torsional registration of the bitoric customized ablation," he concluded.