LASIK outcomes are optimized thanks to advances in technique and technology

February 15, 2008

LASIK in 2007 represents a wonderful world that can provide excellent efficacy, safety, and stability.

Key Points

New Orleans-Refractive surgeons and their patients are now enjoying a "wonderful world" thanks to advances in technique and technology that have optimized the outcomes of LASIK, said Thomas F. Neuhann, MD, at the refractive surgery subspecialty day preceding the annual meeting of the American Academy of Ophthalmology.

Dr. Neuhann, professor of ophthalmology, Tech University of Munich, Germany, delivered a keynote address during a section of the meeting devoted to LASIK. He reviewed the features of LASIK that underlie its popular appeal and the developments responsible for maximizing its results and minimizing its risks. Looking to the future, Dr. Neuhann told attendees that he has hopes for even more progress.

"No new world is so wonderful that it cannot be improved," he said.

The relative comfort of LASIK, combined with the immediacy of its vision results and overall excellent efficacy, predictability, stability, and safety, account for its marketplace success, he said. The advances that have contributed to today's "wonderful world of LASIK" are apparent just by comparing the procedure in 2006 versus 2000, Dr. Neuhann added.

"Over that relatively short period, we have benefited from the introduction of better technology for flap creation, improved ablation profiles, three-dimensional tracking systems, and centration on the visual axis rather than the pupillary center," he said.

Clinical results document the impact of those developments. Dr. Neuhann reported that in a contemporary series of 319 consecutive patients, more than 90% of eyes were corrected to within 0.5 D of the intended target for both sphere and cylinder. In addition, both the safety index and the efficacy index for the cohort exceeded 1, and few re-treatments were performed in the series.

Better hardware represents a major area of progress in LASIK, Dr. Neuhann said, although the basis for the advances has been improved understanding of optics and causes of complications. The ability to scan the anterior and posterior surfaces of the cornea together with refined software algorithms have improved detection of eyes at risk for ectasia and reduced rates of its occurrence, he said.

Wavefront measurements have been enhanced because sensors are acquiring more measurements with reduced dependency on interpolation. Further, technology now allows surgeons to correlate the topography and wavefront data and differentiate between the relative contributions of the various refractive elements of the eye.

Pupillometry also has improved with the availability of infrared technology that enables quantitative measurement of the low mesopic pupil size; the result is the determination of a more realistic optical zone, Dr. Neuhann said.

The introduction of the femtosecond laser as well as improvements in that technology and in mechanical microkeratomes allow LASIK flaps to be created with better precision and reliability in terms of thickness as well as with fewer complications.

"With the opportunity to create thinner flaps reliably, we have hope of seeing earlier reversal of postoperative neuroparalysis, and there is also promise for using pharmacologic modalities, such as cyclosporine A, to promote earlier flap reinnervation," Dr. Neuhann said.

Thanks to improved ablation profiles, including wavefront-optimized and wavefront-guided profiles, surgically induced aberrations also have been minimized, he said.

"This has been a great step forward, and while we have not yet reached our goal with respect to correcting aberrations, performing customized ablation in individual eyes helps us avoid one of the most dreaded surgical complications: low-visual-quality vision at mesopic illumination," he said.

The question of the best technique for ablation centration remains controversial, Dr. Neuhann said, although at least for hyperopic treatments, it is has been demonstrated that centration on the first Purkinje image is preferable to pupil-based centration. Meanwhile, vast improvements have occurred in the realm of intraoperative monitoring, with laser platforms now featuring cyclorotational and z-axis tracking for better ablation precision. In addition, new lasers have optional integrated online pachymetry systems that allow real-time determination of flap thickness and ablation depth for improved safety in primary procedures or re-treatments.