Individualizing post-cataract surgery spherical aberration improves contrast sensitivity

Because the Tecnis IOL is designed with a spherical aberration of -0.27 µm, targeting for an average residual spherical aberration of about +0.1 µm may result in better contrast sensitivity after cataract surgery, according to a study by a researcher in Canada.

George H.H. Beiko, BM, BCh, FRCSC, compared the contrast sensitivity between two groups of cataract surgery patients implanted with the Tecnis aspheric IOL (Advanced Medical Optics). The first group included 13 consecutive patients with at least +0.33 µm of preoperative spherical aberration. The second group included 20 consecutive patients without the specified amount of preop spherical aberration, according to the study.

Dr. Beiko measured contrast sensitivity for distance under photopic and mesopic conditions at 3 to 5 weeks follow-up.

Preoperatively, spherical aberration averaged +0.37 µm in the first group and +0.291 µm in the second group.

At follow-up, patients in the first group had better contrast sensitivity. Additionally, Dr. Beiko found statistically significant differences in contrast sensitivity between the two groups at the spatial frequencies of 6 cycles per degree and 12 cycles per degree under photopic (P = .0267 and P = .0215, respectively) and mesopic (P = .0356 and P = .0217, respectively) conditions, according to the study.

"Targeting for a postoperative mean residual spherical aberration of approximately +0.1 µm by selecting patients according to their preoperative spherical aberration resulted in better contrast sensitivity," Dr. Beiko said.

The study is published in the August issue of Journal of Cataract & Refractive Surgery.