Nevertheless, the objective must be directed to a final low spherical aberration, which allows the patient good contrast sensitivity. 3 It is impossible to completely correct the spherical aberration in all our patients as there is an interaction between much more complex aberrations than a sum of the existing spherical aberration and the intraocular lens induced aberration. suggests that a quantity of positive spherical aberration can be correlated with visual acuities of 20/15 or better. A study performed on pilots of the American Air Force by Grimson et al. Some studies suggest that it is not necessary to correct spherical aberration completely, and in fact it is recommended to leave a slightly positive residual (+0.10 μm). Based on this concept, intraocular lenses were developed with negative spherical aberration, which simulate a young lens that compensates for the average positive spherical aberration of the cornea. This positive spherical aberration of the cataractous lens adds to the spherical positive aberration of the cornea, impairing the visual quality of patients. Spherical aberration of the lens changes over time unlike spherical aberration of the cornea, going from negative to positive as cataracts develop. 2 The natural crystalline compensates for this positive spherical aberration, inducing a negative spherical aberration of –0.20 μm, leaving a slightly positive total aberration of +0.10 μm. The average spherical aberration of the anterior cornea surface is slightly positive (between +0.27 and +0.30 μm), remaining stable throughout life. Spherical aberration generally reduces retinal image contrast and affects visual quality, especially under mesopic conditions. Spherical aberration is included within the high order aberrations, specifically in the group of fourth order aberrations, along with quatrefoil and secondary astigmatism. In an aspherical lens, the rays of light passing through the center do not focus at the same point as the rays passing through the periphery of the lens. The word “aspheric” is used to describe a surface or in this case a lens that does not have a spherical shape. There are multiple intraocular lens options that can correct this aberration, but when and how we should use them is a topic of debate and research in recent years. Among the high order aberrations that can be corrected with cataract surgery is spherical aberration. This is due to several factors, including problems with the ocular surface, pseudophakic dysphotopsia, and optical aberrations in general.Īlthough low order aberrations (myopia, hyperopia, and regular astigmatism) have a greater impact on vision, high order aberrations also play an important role, especially in patients who are candidates for multifocal lenses. While it is common to see patients post-cataract surgery with a visual acuity (VA) of 20/20, many patients remain dissatisfied with their quality of vision. Today the goal of cataract surgery is to provide patients with the best possible quality of vision. By Claudio Orlich, MD ALACCSA shares a recent article on spherical aberrations from one of its contributors
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