Custom ablation with new integrated laser system improves visual quality

Postoperative wavefront analysis shows a significant reduction of optical aberrations in study.

Issue: June 1, 2004

ByMichela Cimberle

ROME – Customized LASIK treatment with the new Nidek Advanced Vision Excimer (NAVEX) laser system can achieve excellent refractive results and enhance visual quality, according to one surgeon.

“The system is very versatile, as you can select from different ablation profiles and optical zone diameters. So you can really tailor the ablation to the patient’s cornea, taking away the minimum amount of tissue and reducing optical aberrations,” said Ermanno Scerrati, MD.

The NAVEX system combines the Nidek OPD-Scan topo-aberrometer, Final Fit customization software and the Nidek EC-5000 excimer laser. The OPD-Scan provides preoperative and postoperative topography and aberrometry, as well as retinoscopy for manifest refraction measurement. The data are then processed by the Final Fit software, which produces a customized treatment program.

“The surgeon can follow the indications given by the computer or introduce any variation he or she wants. The final data are then transferred into the laser that performs the customized treatment,” Dr. Scerrati explained.

“One of the advantages is that you know beforehand what you are going to obtain from a morphological, refractive and aberrometric point of view, and you have plenty of freedom in modifying any of these data,” he added.

Source: Scerrati E

Saving tissue

Tissue-saving capability is another important advantage of the NAVEX system.

In all the eyes he treated, Dr. Scerrati used small 4.5-mm optical zones with large, smooth transition zones.

“This is the best treatment option particularly for medium-high refractive errors in eyes with reduced corneal thickness. From the patient’s point of view, it is just like having a 9.5- to 10-mm optical zone, but much less tissue is removed,” he said.

“Smooth transition zones also prevent night halos and glare, and have the same capability of reducing aberrations as large optical zones.”

The system is flexible, allowing for whatever optical zone diameter is wanted. The best ablation profile can also be selected from seven options of corneal asphericity, Dr. Scerrati said.

“Up to now we have only used profile n4. The more you get up in the scale, the better the results will be in terms of corneal morphology, but you will remove an increasingly greater amount of tissue,” he explained.

Final Fit software displays a breakdown of the ablation into spherical, cylindrical and irregular components.

Image courtesy of Nidek

Preliminary data

In a preliminary study, the results of 10 eyes of five patients treated with the NAVEX system were analyzed. Mean age of the patients was 35 years, mean spherical equivalent was –2.84 ± 0.97 D. Dr. Scerrati performed a standard LASIK flap with nasal hinge, using a Nidek MK 2000 microkeratome. All patients were examined at day 15, 1 month and 3 months after surgery.

“We had very stable, predictable results. The mean SE at 3 months was +0.04 D. Uncorrected visual acuity was 20/15 or better in six eyes, 20/20 or better in three eyes and 20/25 or better in one eye. Unaided vision was equal to preoperative BCVA in four eyes and 1 line better in six eyes,” he said.

Postoperative OPD-Scan wavefront analysis showed a significant reduction of optical aberrations. Three months after surgery, total RMS decreased from 4.194 preoperatively to 1.108.

Individual aberrations, like spherical aberration and coma, were also significantly reduced, the study showed.

“By treating the aberrations, particularly spherical aberration and coma, the NAVEX customized system improves visual quality. There is no contrast loss, as in conventional LASIK, but rather an increase in contrast sensitivity. The most striking difference with conventional LASIK is the quality of night vision, which is sharp and clear, without problems of halos and glare,” Dr. Scerrati pointed out.

Further studies on a higher number of patients are in progress.

Source: Scerrati E

For Your Information:

Ermanno Scerrati, MD, can be reached at Via Marittima 210, 03100 Frosinone, Italy; phone/fax +39-0775-858101; e-mail: ermaeye@virgilio.it.

Nidek, manufacturers of the NAVEX laser system, can be reached at 47651 Westinghouse Dr., Fremont, CA 94539-7474; e-mail: contact@nidek.co.jp; Web site: www.nidek.com.