Tilt, decentration of spherical, aspheric IOLs leave optical quality unaffected

J Cataract Refract Surg. 2009; 35(6):1006-1012.

Issue: September 25, 2009

Normal degrees of spherical and aspheric IOL tilt and decentration did not adversely affect optical quality, a study showed.

“Tilt and decentration of IOLs implanted in the capsular bag in eyes with an intact lens capsule and zonule have, on average, decreased to an optically almost negligible amount, comparable to that of the natural crystalline lens,” the study authors said.

The randomized study included 21 patients with a mean age of 71 years. Patients were randomly assigned to receive a spherical Sensar AR40e (Abbott Medical Optics) in one eye and an aspheric Tecnis Z9000 (AMO) in the other eye. Patients were masked to the IOL types they received in each eye.

Investigators assessed ocular wavefront error and calculated higher-order aberrations at 3 to 4 months after surgery. They used Scheimpflug photography to measure postoperative IOL position.

The spherical IOL showed a mean optic tilt of 2.89°, and the aspheric IOL showed a mean optic tilt of 2.85°. The spherical IOL showed a mean optic decentration of 0.19 mm, and the aspheric IOL showed a mean decentration of 0.27 mm.

Neither IOL type significantly affected best corrected visual Strehl ratio of the optical transfer function for a pupil diameter of 3.5 mm, the authors said.

Aspheric and spheric IOLs were similar in amounts and rates of tilt and decentration in an intraindividual setting. The amounts were minor and did not reduce the quality of vision for either IOL type. Minor tilt and decentration of an aspheric IOL did not decrease the amount of correction of the spherical aberration or decrease retinal image quality. This study reassures surgeons who implant aspheric IOLs that if the IOL is slightly tilted or decentered, this will not greatly impact the quality of vision afforded by the negative asphericity.

– Bonnie An Henderson, MD
OSN Cataract Surgery Board Member