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Do not rely on eye tracking systems alone: surgeon
Researchers found a relationship between high myopia and poor decentration with and without the aid of tracking systems.
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LISBON — Monitoring the patient and ensuring proper light fixation during refractive surgery are still important for proper centration, despite advances in eye tracking systems, one surgeon says.
“Perfect stabilization is impossible,” Ahmed Osman, MD, told attendees at the European Society of Cataract and Refractive Surgeons meeting. Dr. Osman, professor of ophthalmology at Alexandria University in Egypt, presented a study comparing tracker-asssisted and manual ablation zone centration in 180 eyes.
Dr. Osman performed LASIK for myopia and myopic astigmatism in two groups. Group 1 included 120 eyes of 60 patients who underwent LASIK using tracker-assisted ablation with the Carl Zeiss Meditec MEL-70 G-scan flying-spot excimer laser or the Visx Star S4 IR laser. Group 2 included 60 eyes of 30 myopic patients treated with the Nidek EC-5000 laser without an eye tracker.
The decentration measurement was determined by the distance between the pupillary center and the center of the ablation on a difference map with a normalized scale of corneal topography. Mean decentration was similar in the two groups: 0.57 mm in group 1 vs. 0.52 mm in group 2. Decentration was found to be more common in patients with high myopia, he said.
“Eye tracking systems are important for centration, but we should not rely on them alone,” Dr. Osman said.
Higher myopia, more decentration
The researchers analyzed the relationship between the degree of myopia and decentration and found that there was a significant association.
“Decentration was significantly more severe in the high myopia,” Dr. Osman said. According to his results, the mean amount of decentration in eyes with low myopia in the tracker-assisted ablation group was 0.32 mm vs. 0.76 mm in eyes with high myopia. In the nontracker-assisted group, the mean amount of decentration in eyes with low myopia was 0.41 mm vs. 0.85 mm in eyes with high myopia.
“The greater the diopters of myopia, the greater the decentration,” he said.
The researchers measured contrast sensitivity under low and high illumination conditions both with and without correction.
There was a trend toward better postop best corrected visual acuity at various levels of contrast sensitivity with tracker-assisted ablation under low illumination conditions. Dr. Osman added that there was a significant difference under low contrast conditions after the 1 month and 3 month follow-up. Dr. Osman maintained that ophthalmologists must continue to play a proactive role in monitoring patient light fixation.
For Your Information:
- Ahmed Osman, MD, is a professor of ophthalmology at Alexandria University. He can be reached at aosman@dataxprs.com.eg. Dr. Osman has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Jared Schultz is an OSN Staff Writer who covers all aspects of ophthalmology. He focuses geographically on Europe and the Asia-Pacific region.