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Age-related small pupil size may impact effectiveness of aspheric lenses
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 David Spalton |
ISTANBUL, Turkey — Aspheric lenses are effective in reducing spherical aberration, but this effect was clinically irrelevant in the majority of cataract patients due to the age-related small pupil size, according to a study carried out at St. Thomas' Hospital, U.K.
In a comparison of aspheric, spheric and neutral IOLs, aspheric lenses did not show significantly different visual acuity outcomes in mesopic or photopic conditions.
"Only contrast sensitivity in mesopic conditions was better, but the advantage was related to the larger pupil size, which we won't find in our average cataract patients," David Spalton, MD, said at the winter meeting of the European Society of Cataract and Refractive Surgeons. "When we asked our patients, who were implanted with a spheric and an aspheric lens in the two eyes, they could not tell the difference."
Improvement with aspheric lenses is a pupil-size dependent phenomenon, Dr. Spalton said.
With the average 4-mm diameter pupil of 70-year-old patients, the effect of correcting spherical aberration is a relatively small contribution in the wavefront error, which is "lost in the total noise of sphere and cylinder," Dr. Spalton said.
However, there is little downside to these lenses, Dr. Spalton said.
"There is no damage in implanting them, and there is possibly some gain in younger patients and in those with larger pupils. There may also be some benefits in asphericity with diffractive multifocal IOLs in reducing halos and glare," he said.
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