Eyeworld Supplements

Dr. Wörtz: I know I'm in the minority on this, but I like to make a relatively large capsulorhexis of about 6.0 mm, espe- cially in younger patients. Sam Masket, MD, and Nicole Fram, MD, have shown convincing evidence that by reverse optic capture, negative dysphotopsia can be eliminated. This has led me to start making a larger rhexis so that I do not have much, if any, anterior capsule optic overlap. While I don't place the optic in the sulcus, it still has dramati- cally reduced the incidence of negative dysphotopsia, and it also ensures that the optical zone isn't reduced by capsular phimosis over time. Good centration is also critical, especially with multifocal IOLs. The best clinical marker for centration is the subject-fixated coaxially sighted corneal light reflex, as Chang and Waring have recently described. 18 Finally, the ocular surface has a huge impact on quality of vision. The tear film is the first refractive interface and can be the rate-limiting factor. For any patient with more than trace to Grade 1 SPK, I think we have to be willing to "press pause." We need to treat the underlying meibomian gland dysfunction or other ocular surface problems before proceeding with surgery. Otherwise, we can't even accurately calculate the IOL power and axis, let alone guarantee high-quality vision after surgery. Dr. Kieval: Keep in mind that significant lens decentration or tilt can negate the benefits of asphericity. The femtosecond laser is a wonderful tool to aid in lens positioning and centration. In particular, being able to customize centration of the anterior capsulotomy is helpful in allow- ing the lens to center accurately. Dr. Garg: I think IOLs usually center on the equator of the bag, so a capsule-cen- tered opening works well in most eyes, especially if you perform diligent surgery with meticulous cortex removal. How- ever, in patients with large angle kappa, there is a high risk of visual quality degradation because it's very difficult to molecules with the lens polymer. Glistenings don't usually require surgical intervention, at least in the short term, but the degree of opacity increases incrementally over the long term, which correlates exactly with my clinical experience. In addition, even the relatively minor 10–20% reduction in light transmission may be more problem- atic in the context of multifocal IOLs that already reduce light transmission. Dr. Chang: How important is it to you to minimize changes in lens thickness across the dioptric range of an IOL platform? Dr. Ma: I think it's definitely worth paying attention to. The smaller the variation in lens thickness, the more predictable the effective lens position (ELP) will be throughout the full range of dioptric power. If there is a large varia- tion, it is more difficult to predict ELP and, therefore, the refractive outcome. The ability to control the thickness range is related to both material and design. The material's index of refraction gov- erns the thickness required to achieve the appropriate change in curvature over the dioptric range, and certain design features can help to compensate for vari- ation in thickness. We recently presented a paper at the 2014 ESCRS in London on a method for using three-dimensional morphology from intraoperative OCT in femtosecond ReLACS to predict postoperative lens position. A secondary outcome of this paper was that lens thicknesses do matter when we consider the accuracy that we can potentially achieve with this meth- odology. Dr. Wörtz: I'm not as concerned about this from an optics perspective, but I do like a platform where I can standardize the incision size and the injector car- tridge regardless of the IOL power. It's just one less thing to worry about. Dr. Chang: Beyond the optics of the IOLs themselves, what are the surgical factors we can control that affect image quality? as they perform well even when the pu- pil is dilated under scotopic conditions. Dr. Kieval: I agree. Ideally we want vision under mesopic conditions to be the same as photopic vision, and it's easier to meet that standard with a lens that is less pupil-dependent. I am particularly cognizant of higher-order aberrations like spherical aberration because these increase in magnitude with a larger pupil. Scotopic vision is more reliant on blue and violet wavelengths of light, so I'm also more concerned about chro- mophores that block this part of the spectrum at night. We are talking about all of this in the context of night driving but good mesopic and scotopic vision are needed in lots of other situations. They are very important, for example, for mechanics, ultrasound technicians, and many others who routinely work in dim light conditions even during the day. Dr. Chang: Do you think glistenings in the lens optic are a serious problem in terms of visual performance? Dr. Ma: Certain materials are known to be prone to glistenings or microvacu- oles. 15 The visual consequences aren't uniform but they can and do matter in some patients. Furthermore, there is good evidence that glistenings worsen with time. 16 What may not be visually significant at the 4- to 5-year mark could become visually significant a decade after that. With longer life expectancies and earlier implantation of IOLs in refractive cataract surgery, this is a major concern. I have personally had several cases now in which the patient's vision was compromised by glistenings and the lenses had to be explanted 15 years after surgery. After IOL exchange, the vision returned to 20/20 so I am confident the loss of acuity was due to glistenings, rather than other causes. Just recently, at the 2014 ESCRS meeting, the top video prize went to a film that discussed the opacification of IOLs. 17 A key point in the film is that opacification in hydrophobic lenses from glistenings results from the tem- perature-dependent interaction of water 7

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