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B. Tan, L. Shi, Y.-L. Chen, J. W. L. Lewis, M. Wang; Spherical Aberration in the Enhancement of Presbyopia Vision. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1122.
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To investigate the contribution of spherical aberration in presbyopia vision.Background: In the recent years, case observations suggested that inadvertently induced spherical aberration from surgical procedures such as the Schachar’s sclera band procedure and the use of intraocular lens produce "pseudoaccommodation" in presbyopia patient vision.
We use optical eye modeling techniques to examine the effect of spherical aberration on the vision of presbyopia patients. The Navarro eye model is constructed in ZEMAX, and a Zernike phase plate is utilized on the surfaces of either the anterior cornea or the lens to produce spherical aberration of the desired magnitude. Patient vision is simulated using Snellen letter E that is equivalent to 20/20 for distant (20’ or 6 meters) and reading distances (14" or 35 cm). The point spread function and Strehl ratio were obtained for various degrees and types of spherical aberration from far distance to close range.
The multifocal effect of spherical aberration increases the focus depth of the eye and creates the "pseudoaccommodation. The depth of focus increases monotonically with the amplitude of positive spherical aberration. For the 5 mm pupil diameter condition, as the spherical aberration increases to approximately 10 times that of the population statistical mean value, the focus depth extends from distance of 6 meters to the reading distance of 35 cm. There is no noteworthy difference in the optical performances between the eyes of the cornea- and lens-originated spherical aberration. We also successfully produced the realistic simulation of the retinoscopic hourglass reflex observation with the eye modeling computation.
From our investigation, presbyopia vision could be appreciably improved by including high-degree of spherical aberration on either the contact lens or the intraocular lens. Surgical approach will require careful calculation to produce the desired degree of spherical aberration.
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