Postoperative Total Wavefront Pattern Between Two Types of Intraocular Lenses Implanted in Cataract Surgery

With the advancement of cataract eye surgery and wavefront sensors, the previously unquantifiable refractive measurements have been identified and the high order aberrations have shown their effect on high resolution imaging. In the human phakic eye, the shape of the normal cornea induces average positive spherical aberration and remains unchanged over time, whereas the crystalline lens has a negative spherical aberration. As a result, overall spherical aberration in the young eye is low. However, the compensation slowly decreases with the aging lens and is fully lost after cataract extraction and implantation of a standard intraocular lens. Optical studies showed that conventional biconvex spherical intraocular lenses add their intrinsic positive spherical aberration to the positive spherical aberration of the cornea resulting in image imperfection and blur. As a useful side effect, this also increases the depth of focus -often referred to as pseudo-accommodation. New Aspheric intraocular lenses designs currently in use impart negative spherical aberration, about 0.17 to 0.20 microns of negative spherical aberration. This added negative spherical aberration partially corrects the average amount of corneal positive spherical aberration \& compensate for its effect. Our study will include (FocusForce foldable aspheric intraocular lens, Bausch \& Lomb, New Jersey, USA) as an example of this type of negative spherical aberration intraocular lenses. In order to improve retinal image quality without compromising depth of field, or introducing other aberrations, aberration-free aspheric intraocular lenses were developed with no inherent spherical aberration. The other intraocular lens targeted in our study (Akreos AO Microincision lens, Bausch \& Lomb, New Jersey, USA) is an example of this type of IOLs.