EyeWorld Asia-Pacific June 2014 Issue

16 June 2014 EWAP FEAturE Views from Asia-Pacific Brendan VOTE, MD Associate Professor, Launceton Eye Institute eye.vote@me.com Shaun EWE, MD Tasmanian Eye Insitute shaunewe@gmail.com 36 Thistle St. West, South Launceston, TAS 7249 Tel. no. +03-63441377 Fax no. +03-63441577 W e read the article “Femtosecond laser-assisted cataract surgery complications” with interest and would like to share some comments and our experiences using the Catalys Precision Laser System (Abbott, Santa Ana, Calif., U.S.) since 2012. We have data on over 4,000 cases (1,852 Laser [LCS] vs. 2,228 Phaco [PCS]) performed by five surgeons as part of our ongoing prospective comparative cohort study. We were unable to proceed with femtosecond laser treatment in some patients (1.5%) due to patient factors including: patient anxiety/claustrophobia (despite anxiolytics); small palpebral apertures notaccommodating the Liquid Optic Interface (LOI); spinal deformity (e.g. kyphosis) preventing positioning on the treatment bed; and inability to obtain suction due to anatomic variations (e.g. deep set sockets, marked conjunctivochalasis). A further 3% of cases were aborted during the procedure (with incomplete treatment), most often due to vacuum break or patient movement beyond safe proceeding guides (patient vector monitoring). Thus, nearly 1 in 20 patients did not receive the intended “planned” treatment. Aside from tilted docking impacting guidance imaging and treatment delivery, OCT recognition of anatomical structures often require manual adjustment (especially limbus and pupil recognition). Failure by the surgeon to recognize and adjust treatment accordingly has the potential for treatment problems such as more anteriorly located incisions than desired. In addition to minor conjunctival hemorrhage from suction, which is common, we found 1.65% of LCS pupils did not remain stable (vs. 0.65% PCS, p=0.004) often requiring intraoperative Malyugin rings or iris hooks. Additionally, 0.66% of LCS cases were noted to have corneal haze intraoperatively, presumably due to suction effects on the cornea (vs. 0.05% PCS, p=0.001). As identified, incomplete capsulotomy can occur (1.39% in our LCS cohort), and capsulotomy removal should follow the contour of the capsulotomy. Anterior capsular tags were also common at 1.62%. A complete capsulotomy does not preclude anterior capsular (radial) tears from developing and we have previously published on this. 1 Radial tears occurred in 1.84% of our LCS cases vs. 0.22% of our PCS cases (p=0.0001). There was no evidence for learning curve effect in our cohorts, rather ultrastructural features on scanning electron microscopy showed LCS to have an irregular edge with pitting, tags and “postage stamp” perforations. We believe fixational eye movements are a factor. Once present, these defects predispose to radial tear formation during subsequent normal intraoperative manipulations. Early recognition does not prevent them but may limit their extension to the posterior capsule. Patient case-mix will likely be relevant to different rates reported by surgeons, with our objective lens densitometry measured by Oculus Pentacam at 2.9 in both cohorts. There was no statistical difference in posterior capsule tear rates between our cohorts. Postoperative complications also suggest some safety signals for LCS. Despite topical NSAID pretreatment, CME was more likely to develop after LCS than PCS (p=0.04). Also, posterior capsule opacity was 50% more likely to develop after LCS than PCS (p=0.01). In summary, while LCS may be as safe as PCS and complication rates are likely to improve with time, we do not think LCS can yet be considered safer than PCS. Complications aside, cost remains the major barrier to surgeon acceptance of this technology. Our cost-effectiveness analysis 2 modeled various outcome and complication scenarios and highlighted that a significant reduction in cost to patients is the only thing that might make this technology cost-effective (even if perfect outcomes are achieved, at current cost to patient it would not be cost effective). References 1. Abell RG, Davies PEJ, Phelan D, Goemann K, McPherson ZE, Vote BJ. Anterior capsulotomy integrity after femtosecond laser-assisted cataract surgery. Ophthalmology 2014;121:17-24. 2. Abell RG, Vote BJ. Cost-effectiveness of femtosecond laser-assisted cataract surgery versus phacoemulsification cataract surgery. Ophthalmology 2014; 121:10-16. Editors’ note: Drs. Ewe and Vote have no financial interests in their comments.