This article is more than 5 years old. Information may no longer be current.
LASIK offers positive outcomes for compound myopic astigmatism with high cylinder
Click Here to Manage Email Alerts
Using a new-generation excimer laser for LASIK on patients with compound myopic astigmatism and a high level of refractive cylinder was found to be safe, effective and predictable, according to a retrospective study.
“We wanted to share the good outcomes that were obtained when treating high levels of astigmatism that previously showed unpredictable results,” lead author Jorge L. Alió, MD, PhD, an OSN Europe Edition Board Member, said.
The study included 37 eyes of 29 patients. All LASIK procedures were performed with the sixth-generation Amaris excimer laser (Schwind eye-tech-solutions).
“This laser incorporates several improvements: different levels of fluence, compensation of the cosine effect, fast repetition rate, flying spot and aspheric ablation profile, and high-speed eye tracker,” Alió said.
Positive results
The main preoperative sphere for study eyes was –2.72 D (range: –8 D to –0.25 D), and the mean preop cylinder was –3.61 D (range: –5.25 D to –3 D).
At 6 months postop, 94% of eyes achieved uncorrected distance visual acuity of 20/40 or better, 84% achieved 20/30 or better and 61% achieved 20/20 or better.
“These are better visual outcomes than we expected,” Alió, who performed 90% of the LASIK procedures, said.
No eye lost two lines of corrected distance visual acuity. All eyes achieved a corrected distance visual acuity of 20/40 or better, and 77% achieved a corrected distance visual acuity of 20/20 or better.
Predictability was better than anticipated, with 87% of eyes achieving a targeted spherical equivalent within ±0.5 D and 97% within ±1 D.
At 6 months, 67% of eyes achieved astigmatism of 0.5 D or less, and 93% achieved 1 D or less.
Only 7.5% of eyes were re-treated. “This was a lower rate than we expected, and three times lower than before,” Alió said.
The study found no significant induction of anterior corneal higher-order aberrations, a common occurrence following correction of high astigmatism.
Safer, more efficient treatment
The aspheric profile of the new-generation excimer laser “allows us to perform more regular corneal ablations with a smooth transition zone, which is where most of the corneal aberrations can be induced,” Alió said. “The Amaris considers a focus-shift balance, due to tissue removal and a compensation factor when the laser hits the periphery of the cornea in a non-normal incidence. This phenomenon is often referred to as the ‘cosine effect,’ in order to avoid the induction of aberrations and to balance the aberrations which are present in the treated eye.”
Alió recommended double-checking with the technician regarding the treatment design performed previously with the ORK-CAM software (Schwind eye-tech-solutions).
In addition, clinicians should register the eye image that was taken with the topographer and compare it with the eye-tracker image under the excimer laser just before beginning the corneal ablation, Alió said.
“This will guarantee the activation of the static and dynamic cyclotorsion. This is very important in order to achieve an effective centration of the treatment, which is a fundamental step in treating high levels of astigmatism,” he said. – by Bob Kronemyer