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A multifocal silicone IOL seems to provide better overall vision to patients compared with other lenses available to correct presbyopia.
"[This] multifocal IOL is an excellent tool for combating presbyopia," said Dr. Black, Sunshine Eye Clinic, Sunshine Coast, Queensland, Australia. "Cataract surgery is refractive surgery. Even though we think of emmetropia as 20/20 or 6/6 vision, our patients are beginning to request more in the way of near vision performance. The ideal IOL would provide great distance vision and consistent and excellent near vision without photic phenomena."
Industry and ophthalmologists, he said, have been on a quest to overcome presbyopia.
With an accommodating lens (crystalens, eyeonics), he found that patients achieved good distance vision without photic phenomena, but the patients could not read well, Dr. Black said.
He demonstrated light passing through an Array IOL and the numerous foci. "This helped me understand why patients were having difficulty reading and were having adverse phenomena," he said.
Dr. Black added that, when he observed light passing through the multifocal silicone IOL under study-which was supposed to be a bifocal IOL with clear far and near focal points-he had hopes that the visual results would be more promising.
The three-piece design of the newer multifocal silicone lens he studied provides excellent centration and has a large optic, according to Dr. Black. The diffractive nature of the IOL facilitates equal distribution of the light from near and far.
In addition, the gratings extend to the edge of the optic, making the vision independent of pupil size. The IOL also has a 4.0-D add, which should allow patients to read well.
A comparison of this multifocal silicone IOL with an apodized diffractive lens (AcrySof ReSTOR, Alcon Laboratories) indicated that the multifocal silicone IOL appeared to provide better contrast sensitivity, he said, adding that he has been using a monofocal version of the silicone lens for a year and has been "very happy with the results."
Dr. Black reported the results on the first 48 eyes (24 patients) with 1-month follow-up after implantation of this multifocal silicone IOL. All patients had hyperopia, and all had good best-corrected distance vision. Following implantation of the lens, the patients had only mild photic phenomena that were not debilitating.
"The vast majority of the patients are within 0.5 D of emmetropia after surgery," Dr. Black reported.
Patients who received the multifocal silicone IOL, he said, were able to read 5-point type on a reading card under a variety of lighting conditions, compared with patients who had crystalens or Array IOLs implanted and could not read type that small.
"I quantitated their reading ability by using a reading speed test that was validated in the past. I use 6-point test type with distance correction in place. The average bilateral reading speed of the selected passage was 48 seconds with a standard deviation of 10 seconds," Dr. Black said.
"The controls were a group of Air Force pilots who read the passage in 47 seconds with a similar standard deviation. This [finding] confirms my clinical impression that the patients have superb reading performance. This is the key to a successful outcome with a multifocal lens. There must be a positive to outweigh the negatives," he said.
The multifocal silicone IOL is not yet available in the United States.