Spherical Aberration and Depth of Focus

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Rocha et al1Rocha K.M. Soriano E. Chamon W. et al.Spherical aberration and depth of focus in eyes implanted with aspheric and spherical intraocular lenses; a prospective randomized study.Ophthalmology. 2007; 114: 2050-2054Abstract Full Text Full Text PDF PubMed Scopus (103) Google Scholar state that “the optical depth of focus between spherical and aspherical IOLs has not been compared in vivo.” There is a good reason for this. As defined, depth of focus is an optics concept that measures the tolerance of placement of the image plane in relation to the lens. It is a measurement of the distance between the lens and the object of regard, wherein the object remains sharply in focus. This is something that is difficult to do in vivo; the factors that affect pseudo accommodation come into play. The authors have conveniently changed the definition of depth of focus to “distance corrected near and intermediate vision.” This is not correct. It creates confusion and the title of the manuscript should be restated to reflect what was truly measured.With respect to the findings, the authors found that distance corrected near visual acuity was better in patients who had smaller pupils. The difference in visual acuity is small and could certainly be attributable to the small difference in pupil size. This is not a new finding. Near visual acuity is better in patients with smaller pupils.2Nakazawa N. Ohtsuki K. Apparent accommodation in pseudophakic eyes after implantation of posterior chamber intraocular lenses.Am J Ophthalmol. 1983; 96: 435-438Abstract Full Text PDF PubMed Scopus (103) Google ScholarTo prove that near visual acuity is better in patients with greater total spherical aberration, the authors would have to go much further in ensuring that the pupil size was controlled. Rocha et al1Rocha K.M. Soriano E. Chamon W. et al.Spherical aberration and depth of focus in eyes implanted with aspheric and spherical intraocular lenses; a prospective randomized study.Ophthalmology. 2007; 114: 2050-2054Abstract Full Text Full Text PDF PubMed Scopus (103) Google Scholar state that “the optical depth of focus between spherical and aspherical IOLs has not been compared in vivo.” There is a good reason for this. As defined, depth of focus is an optics concept that measures the tolerance of placement of the image plane in relation to the lens. It is a measurement of the distance between the lens and the object of regard, wherein the object remains sharply in focus. This is something that is difficult to do in vivo; the factors that affect pseudo accommodation come into play. The authors have conveniently changed the definition of depth of focus to “distance corrected near and intermediate vision.” This is not correct. It creates confusion and the title of the manuscript should be restated to reflect what was truly measured. With respect to the findings, the authors found that distance corrected near visual acuity was better in patients who had smaller pupils. The difference in visual acuity is small and could certainly be attributable to the small difference in pupil size. This is not a new finding. Near visual acuity is better in patients with smaller pupils.2Nakazawa N. Ohtsuki K. Apparent accommodation in pseudophakic eyes after implantation of posterior chamber intraocular lenses.Am J Ophthalmol. 1983; 96: 435-438Abstract Full Text PDF PubMed Scopus (103) Google Scholar To prove that near visual acuity is better in patients with greater total spherical aberration, the authors would have to go much further in ensuring that the pupil size was controlled. Author replyOphthalmologyVol. 115Issue 9PreviewWe thank Dr Beiko, for the comments regarding the paper “Spherical Aberration and Depth of Focus in Eyes Implanted with Aspheric and Spherical Intraocular Lenses: A Prospective Randomized Study.” Cataract surgery and intraocular lens (IOL) implantation is currently evolving into a refractive procedure. Furthermore, the effects of the higher order aberrations induced after the ophthalmic surgical procedures are an important and currently relevant topic to be discussed. The introduction of ocular wavefront analysis in clinical ophthalmology made it possible to quantify total ocular aberrations and can give quantitative measurements that can be translated in qualitative functions like contrast sensitivity. Full-Text PDF