Customized aberration correction could be next step in IOL design
Targeting a spherical aberration of 0.1 µm will help achieve better contrast sensitivity in patients, surgeon says.
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Personalized correction of spherical aberration will be the next step forward in cataract surgery, according to an ophthalmologist who spoke on the topic at last year’s European Society of Cataract and Refractive Surgeons meeting.
George Beiko, BM, BCh, FRCS(C), argued that targeting a postoperative spherical aberration of 0.1 µm will help to achieve better contrast sensitivity in patients after cataract surgery.
“In the same way I wouldn’t give my average IOL patients a 20 D power IOL, I would advocate that we should correct each patient’s spherical aberration individually,” he told the audience in Lisbon.
According to Dr. Beiko, past work in this field has shown that the spherical aberration of the average cornea is about 0.27 µm. The Advanced Medical Optics Tecnis IOL is designed to correct this amount with a corresponding negative spherical aberration.
However, he said he believes that the previously calculated standard deviation of ± 0.02 µm from the mean 0.27 µm is too small, and the patient population is more widely distributed.
Dr. Beiko said his own studies have found a standard deviation of ± 0.119 µm, which means that 99% of patients are within a range of 0.00 µm to 0.60 µm as opposed to the range of 0.21 µm to 0.33 µm suggested by previous work.
“We’re saying, no, you need more than one lens, you need a range of lenses to help everybody,” he told Ocular Surgery News in an interview.
Targeting spherical aberration
Dr. Beiko tested his hypothesis by choosing patients with an existing positive corneal spherical aberration of 0.37 µm and implanting the Tecnis lens, with its spherical aberration of –0.27 µm, to target a postop spherical aberration of 0.1 µm.
He selected 13 patients with this positive spherical aberration value, and he compared those patients to a group of 20 who were not selected for a specific aberration value. The unselected patients had a mean spherical aberration of 0.292 µm.
The corneal spherical aberration was measured using the Oculus Easygraph topographic system. Postoperative contrast sensitivity was measured using the Stereo Optical VT 1600x.
“The group that was chosen for 0.37 µm outperformed under photopic and under mesopic conditions with statistical significance,” he said. “So the hypothesis that, if you target 0.1 µm you get better visual results, seems to hold.”
Achieving majority correction
Dr. Beiko explained that there are other factors that can contribute to a patient’s spherical aberration, including the posterior cornea and the retina, but he said that they count for less than 5% of the performance on contrast sensitivity.
For Your Information:
- George Beiko, BM, BCh, FRCS(C), can be reached at 180 Vine St., Suite 103, St. Catharine’s, ON L2R 7P3, Canada; +1-905-687-8322; e-mail: george.beiko@sympatico.ca. Dr. Beiko has no direct financial interest in any of the products mentioned in this article.
- Jared Schultz is an OSN Staff Writer who covers all aspects of ophthalmology. He focuses geographically on Europe and the Asia-Pacific region.