Commentary: Aspheric intraocular lens may be the future but not always a simple solution.

Abstract

Nowadays, cataract surgery is not only to achieve the vision of 20/20; rather, it demands many other qualities of vision to be fulfilled as described by Despande et al.[1] Spherical aberration is one of the varieties of higher-order aberration (HOA) in the eye. The optical design of the aspheric intraocular lens (IOLs) reduced spherical aberrations and increased contrast sensitivity as described by Despande et al.[1] As described by the authors, the crystalline lenses lose their property of negative spherical aberration to compensate for the positive spherical aberration of the eye with overall near-zero spherical aberration of the young adult eyes or very minimal spherical aberration. Wavefront technology is used nowadays more frequently by an aberrometer to map the eye before any refractive surgery to detect any aberration so that customized compensatory optical solution can be done to that eye to achieve the best possible functional vision. Patients having age-related cataracts not only suffer from a decrease in vision but also loss of contrast, especially in mesopic conditions. They did not realize it at that time due to cataracts but after cataract surgery when their contrast also improves along with their vision they are the happiest patients. Theoretically, spherical aberrations increase the depth of focus but decrease modulation transfer function at high spatial frequencies at optimum focus. Spherical aberrations, therefore, play an important role in the balance between visual acuity and depth of focus.[2] Although aspheric IOLs are replacing the spherical IOLs in our country, still PMMA rigid IOL is implanted frequently in below poverty line ( BPL) and ration cardholder patients due to the issue of affordability. Another point to be noted is that the asphericity of aspheric IOL is lost and even leads to more aberrations such as coma and coma-like effects if the IOL is slightly decentred and tilted and these aberrations occur more in aspheric IOL than in spheric IOL and monofocal IOL than multifocal IOL in such scenarios.[3] That is the reason in 1980 and 1990 there was a reluctance for aspheric IOL. However, after the evolvement of phacoemulsification, better surgery techniques such as proper rhexis size, the problems of decentration and tilt has got reduced quite a lot so more and more aspheric IOLs are implanted. The spherical aberration reduced significantly in these aspheric IOL in larger pupil aperture such as in young patients who have undergone corneal refractive surgery, especially in mesopic and scotopic conditions. Thus, the aged population with a small pupil size and having less mesopic and scotopic activity may not need the aspheric IOL. Wavefront technology is used more before corneal refractive surgery or biopics, to measure the corneal and total aberration of eyes so that customized surgery can be planned accordingly for a better functional optical outcome. The future generation of cataract surgery will not be for the recognition acuity only rather for fully functional visual outcome and aberration-free vision. With the better technique of cataract surgery, day by day such as higher competency in phacoemulsification and nowadays femto laser-assisted cataract surgery where precise capsulorhexis is done, more and more aspheric IOL will be the choice of IOL in the coming days.