Evolution in wavefront-guided treatment yielding improved visual outcomes

March 1, 2006

Chicago—A number of incremental advances that have occurred in wavefront-guided treatment during the past year have added up to enhance outcomes of these customized procedures significantly, said Capt. Steven C. Schallhorn, MD, at the refractive surgery subspecialty day sponsored by the International Society of Refractive Surgery at the American Academy of Ophthalmology annual meeting.

"The technology that is available to us now has reduced the variability of refractive outcomes, resulting in more patients with a postoperative uncorrected visual acuity (UCVA) that is the same as or better than their preoperative best spectacle-corrected visual acuity (BSCVA). Such results are significantly better than what we were achieving several years ago," said Dr. Schallhorn, director, Cornea and Refractive Surgery, Naval Medical Center, San Diego.

New technology based on iris or scleral vessel recognition to register the wavefront profile with the ablation is one of the recent innovations contributing to improved outcomes with wavefront-guided treatment. To illustrate its impact, Dr. Schallhorn presented UCVA results from a multicenter international study in a group of eyes with ≥1.50 D of cylinder undergoing wavefront-guided LASIK with (n = 59) and without (n = 57) iris registration. While similar proportions of patients in both groups achieved UCVA of 20/25 or better, UCVA of 20/20 or better was achieved by 92% of eyes treated with iris registration technology compared with only 82% of eyes having a procedure without that feature.

Improved laser ablation

Proper positioning of the laser ablation pattern has also been improved by new technology that compensates for pupil centroid shift. This should eliminate the risk of a subtle decentered ablation caused by a shift in the pupil center in those lasers that track the pupil margin. With recent upgrades, lasers now also provide faster treatment times that are likely to improve outcomes.

"Faster treatment speed should improve outcomes because it lessens variability associated with corneal hydration, and also should also translate into better patient fixation," Dr. Schallhorn said.

Studies performed by Dr. Schallhorn and colleagues and by other investigators also showed the potential for keratome choice to influence visual recovery and quality of visual outcomes and demonstrated better results were achieved using the femtosecond laser (IntraLase Corp.) for flap creation compared with a mechanical instrument.

In the study conducted by Dr. Schallhorn and David J. Tanzer, MD, in which the only difference between treatment groups was the keratome used, eyes that had surgery using the femtosecond laser had significantly better low-light contrast sensitivity than the group in which flap creation was performed with a mechanical microkeratome.

"A femtosecond laser-created flap should also allow surgeons to create thinner flaps more consistently, and that in turn should widen our indications for LASIK treatment," Dr. Schallhorn said.