Eyeworld

EW RESIDENTS 110 March 2018 EyeWorld journal club by Sean Hansen, MD, Nakul Shekhawat, MD, MPH, Shahzad Mian, MD T here is increasing appreci- ation for the importance of metrics beyond visual acuity when assessing the quality of patients' vision. With advances in aberrometry, high- er order aberrations (HOAs) have become recognized as one of these metrics. Wavefront aberrometry now allows for quantification of HOAs produced by distinct components of the optical pathway of the eye, such as the corneal surface or internal structures. 1 Refractive surgery has led the way in efforts to reduce HOAs in order to optimize visual outcomes. Parallel to these devel- opments, improvements in surgical technique and intraocular lens (IOL) design continue to advance sur- geons' ability to successfully implant IOLs in an ever-expanding range of patients. In particular, the risk-ben- efit profile of surgery for subluxat- ed lenses has become much more favorable in recent years thanks to the development of new capsular support devices, such as the Cionni modified capsule tension ring and Ahmed segments, 2 as well as newer techniques such as intrascleral IOL fixation. In their study of the effects of lens extraction and IOL implan- tation on HOAs among patients with subluxated crystalline lenses, Srivastava et al. 3 apply these ad- vances to an important new patient population. In this prospective, interven- tional case series, 39 eyes with non-traumatic subluxation of the crystalline lens underwent lens removal with IOL implantation and had pre- and postoperative aberrom- etry performed. All eyes underwent successful capsular bag fixation with in-the-bag IOL implantation, sutured scleral IOL fixation, or intrascleral IOL fixation. Best corrected visual acuity (BCVA), total HOAs mea- sured by root mean square, coma, spherical aberration, and modu- lation transfer function were all found to be significantly improved when comparing preoperative and 6-month postoperative measure- ments. Surgery resulted in statisti- cally significant improvements in all measures of HOAs in all eyes, even for eyes in which BCVA did not improve. Only five eyes did not experience improvement in BCVA, but all of these eyes had pre-existing amblyopia. Based on these results, Srivastava et al. argue that reduction in HOAs may be an indication for earlier surgical intervention in eyes with subluxated crystalline lenses and conventionally acceptable pre- operative BCVA, particularly among younger patients. One of the more intriguing implications of this study is the possibility of reducing the risk of amblyopia among pediatric patients with lens subluxation. Prior publi- cations have discussed the role of HOAs as a potential amblyogenic factor, 4,5 although evidence clearly linking HOAs to amblyopia is still limited. However, with the excep- tion of the five eyes with pre-exist- ing amblyopia, all eyes in this study experienced improvement in both BCVA and HOAs, which weakens the argument for using HOAs as a standalone indication for earlier IOL implantation. The youngest patient in this study was 6 years of age, and only 11 of the 39 eyes (28%) were younger than 15 years of age. There was no subgroup analysis of pediatric patients, which could have yielded valuable information regarding optimal timing of surgery for young patients. The importance of accommodation for pediatric patients' visual development must also be considered. Although lens subluxation likely reduces these patients' accommodative ability somewhat, lens extraction and IOL placement will remove any residual accommodation that exists. Pre- Review of "Comparison of ocular wavefront lenses before and after lens extraction with Comparison of ocular wavefront aberrations in subluxated lenses before and after lens extraction with intraocular lens implantation Samaresh Srivastava, DNB, Vaishali Vasavada, MS, Viraj Vasavada, MS, Shail Vasavada, DO, M.R. Praveen, DOMS, Rajendra Reddy, MS, Abhay Vasavada, MS J Cataract Refract Surg. 2018;44(3). Article in press. Purpose: To compare change in ocular higher order wavefront aberrations (HOAs), visual acuity and modulation transfer function (MTF) following lens extraction with intraocular lens (IOL) implantation for subluxated lenses. Setting: Iladevi Cataract & IOL Research Centre, India Design: Prospective, observational, interventional case series Methods: 39 eyes with subluxated lenses undergoing lens extraction with IOL implantation. Capsular bag fixation with in-the-bag IOL implantation or sutured/sutureless scleral fixation of IOL was performed. Ray tracing aberrometry was performed under mesopic conditions pre- and 6 months postoperatively, and the following were compared: root mean square (RMS) value for total ocular HOAs, coma, spherical aberration (SA), MTF and best spectacle corrected visual acuity (BSCVA). Results: Bag fixation with in-the-bag IOL was performed in 26 eyes, sutured scleral fixation IOL in nine eyes, and intrascleral IOL fixation in four eyes. There was a statistically significant improvement in BSCVA and RMS for total HOAs 6 months postoperatively. RMS value for total HOAs (mean + standard deviation in microns): preop 10.5 ± 9.5 vs. postop 4.73 ± 4.6 (P<0.001), coma (2.46 ± 2.4 vs. 0.11 ± 0.1, P=0.03) and SA (0.37 ± 0.9 vs. 0.02 ± 0.06, P=0.02), respectively. MTF improved significantly in all eyes 6 months postoperatively (0.05 ± 0.02 vs. 0.32 ± 0.16, P=0.005). BCVA improved significantly postoperatively (0.67 ± 0.2 vs. 0.27 ± 0.1 logMAR, P<0.001) at 6 months. Conclusions: Lens extraction with IOL fixation in subluxated lenses led to significant reduction in ocular HOAs and improvement in MTF. This aspect should be kept in mind when deciding timing of surgery for these eyes. venting amblyopia will then depend on effective management of refrac- tive error at near. Additionally, the longevity of scleral sutured lenses has been a topic of concern, with a significant proportion of these lenses becoming dislocated after 7 to 10 years in children. 6 In addition to late dislocation, scleral sutured IOLs implanted in a pediatric population have a high rate of complications during long-term follow up, in- cluding intraocular hemorrhage, choroidal effusion, late endoph- thalmitis, and retinal detachment. 6 Alternatively, a case series of in- trascleral fixated IOLs in a pediatric population showed limited compli- cations, but long-term follow up is nonetheless lacking. 7 Although it is important to consider all options for management of subluxated lenses in pediatric patients, careful evaluation of the risks and benefits of surgery for each individual patient remains critical. Additional research is also need- ed to evaluate the association be- tween HOAs and visual function or quality of life measures. If patients subjectively report improvement in quality of vision from reduction of HOAs while having no objec- tive improvement in visual acuity, surgical treatment to reduce HOAs would have a stronger argument. Compared to leaving patients with lens subluxation aphakic and reha- bilitating their vision using aphakic spectacles or contact lenses, IOL implantation itself could also lead to an improvement in patients' quality of life. Finally, successful positioning of IOLs in this unique patient population can be challenging Shahzad Mian, MD, associate chair for education, University of Michigan Whether and when to remove sub- luxated IOLs or crystalline lenses is a complex decision. I've invited the Michigan residents to review this study on lenticular higher order aberrations that appears in the March issue of JCRS. —David F. Chang, MD, EyeWorld journal club editor

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