EyeWorld Asia-Pacific June 2021 Issue

EWAP JUNE 2021 3 EDITORIAL Graham Barrett Chief Medical Editor EyeWorld Asia-Pacific • China • Korea • India EyeWorld Asia-Pacific • June 2021 • Vol. 17 No. 2 A mong the many interesting articles in our current issue “What’s new in the world of IOLs” is sure to be of interest to the majority of readers. Several pseudophakic options are available to surgeons who would like to offer a solution to their patients’ presbyopia. Many surgeons attempt to custom fit a particular solution to an individual patient depending on factors such as their lifestyle, personality, and occupation. My approach is to select the option that I believe has the greatest likelihood of success as defined by patients’ satisfaction, with the least amount of compromise in their quality of vision—modest monovison. The term monovision encompasses a wide range of myopic defocus in the near eye and the terminology can be confusing. I would suggest that the term mini monovision be used when the anisometropia is set at 0.75 D to 1.00 D; modest monovision at 1.25 D to 1.50 D; and traditional monovision at 1.75 D to 2.50 D. When even smaller amounts of myopic defocus such as –0.5 D or less are targeted in one eye then the term micro monovision would be appropriate. Although total spectacle independence is less frequent with a lower level of myopia, limiting the anisometropia to approximately –1.25 D reduces the likelihood of a reduction in binocular contrast sensitivity, asthenopia, and loss of stereoacuity that can occur with higher levels of anisometropia. Perhaps the most important compromise with modest monovision with target of –1.25 D near eye is the occasional need for spectacles. I suspect that surgeons overestimate the importance of total spectacle independence as an index of patients’ satisfaction after undergoing cataract surgery. Patients typically rank quality of vision and the avoidance of dysphotopsia as more important than total spectacle independence when judging their satisfaction after cataract surgery. What’s new in world of IOLs, however, are extended depth of focus IOLs which are complementary to monovision. I first coined this term in 2012 to describe a modified monofocal lens I designed that utilized 4th and 6th order positive spherical aberration to extend the depth of focus while maintaining optical quality. Positive spherical aberration (SA) and myopic defocus interact in a synergistic fashion such that the combined modulation transfer function (MTF) is enhanced. In addition, when combined with mini or modest monovision the defocus curves of the distant and near eye have a greater overlap maintaining the features of binocular vision and as well as providing greater near acuity for the same level of myopic defocus. In recent years the term “extended depth of focus” has been applied to several IOLs based on different optical principles such as negative SA, low-add diffractive bifocal and trifocal IOLs, and phase shift technology. The term therefore does not describe a homogeneous group of IOL models and features such as the presence or absence of dysphotopsia depends on the optical principles. In addition, not all these IOLs are good for use in combination with myopic defocus as in monovision. Depending on the optical technology, even minor myopic defocus can increase unwanted images or compromise MTF. Modest monovision continues to be an attractive solution to presbyopia and, in my opinion, should be considered a “premium” solution. It requires expert surgery and biometry, knowledgeable selection of IOLs, and the utilization of toric implants to reduce astigmatism. The popularity of this approach is increasing, and when combined with extended depth of focus IOLs could increase spectacle independence while avoiding some of the negative issues associated with multifocal IOLs.