Ruiz Alves M. Comparison of ketorolac 0.4% and nepafenac 0.1% · for the prevention of cystoid macular oedema after phacoemulsifi- · cation: prospective ...
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relevance to 2016, up to 76% of patients in each group had extracapsular surgery by the attending surgeon or by residents in training. It is therefore difficult to undertake a meaningful comparison with patients having laser-assisted cataract surgery today. Current data are available. Tzelikis et al.5 showed in a randomized prospective trial that NSAIDs were not efficacious in preventing macular edema. The authors hypothesize that thermal damage might be intensified as a result of prolonged elevated pressure as docking “reduces cooling due to impaired perfusion.” This was not measured during the study, was not a primary or secondary endpoint, and therefore is speculation. Hypotheses should be carefully phrased, especially when they are not based on study findings. The statement is even more speculative because previous data with the same femtosecond laser found only a minimal increase in intraocular pressure (IOP) and most cases of CME in this study occurred after the software upgrade, which would logically decrease the amount of time the pressure was applied. In conclusion, the study's purpose was to compare the incidence of CME between femtosecond laser–assisted cataract surgery and manual cataract surgery. It found no statistical difference between the 2 groups. It was not designed to show the effect of NSAIDs on either group, nor did it measure IOP before, during, or after laser application. It did not measure retinal blood flow or function or the heat generated by the laser. As such, speculation in the abstract and conclusion that “[i]ncreased CME might be a subthreshold retinal injury safety signal after femtosecond laser pretreatment” is not supported by the design or results in the study. Lewis Levitz, MB BCh, MMed, FCS(SA) Ophth, FRCSEd, FRANZCO Joseph Reich, MB BS, DO (Melb), FRACS, FRANZCO Hawthorn East, Victoria, Australia Timothy V. Roberts, MB BS, MMed (Syd), FRANZCO, FRACS Michael Lawless, MB BS, FRANZCO, FRACS Chatswood, NSW, Australia
REFERENCES 1. Ewe SYP, Oakley CL, Abell RG, Allen PL, Vote BJ. Cystoid macular edema after femtosecond laser–assisted versus phacoemulsification cataract surgery. J Cataract Refract Surg 2015; 41:2373–2378 2. Levitz L, Reich J, Roberts TV, Lawless M. Incidence of cystoid macular edema: femtosecond laser–assisted cataract surgery versus manual cataract surgery. J Cataract Refract Surg 2015; 41:683–686 3. Conrad-Hengerer I, Hengerer FH, Al Juburi M, Schultz T, Dick HB. Femtosecond laser-induced macular changes and
anterior segment inflammation in cataract surgery. J Refract Surg 2014; 30:222–226 4. Rossetti L, Bujtar E, Castoldi D, Torrazza C, Orzalesi N. Effectiveness of diclofenac eyedrops in reducing inflammation and the incidence of cystoid macular edema after cataract surgery. J Cataract Refract Surg 1996; 22:794–799 5. Tzelikis PF, Vieira M, Hida WT, Motta AF, Nakano CT, Nakano EM, Ruiz Alves M. Comparison of ketorolac 0.4% and nepafenac 0.1% for the prevention of cystoid macular oedema after phacoemulsification: prospective placebo-controlled randomised study. Br J Ophthalmol 2015; 99:654–658
--In their nonrandomized single-surgeon prospective comparative cohort case series, Ewe et al.1 contribute to an important topic: Is femtosecond laser–assisted cataract surgery as safe as conventional manual surgery and phacoemulsification, a technique that has an excellent track record and is the most frequently performed surgical intervention? Cystoid macula edema is a special concern to cataract surgeons everywhere since the time it was still associated with the names of Irvine and Gass. Our Australian colleagues deserve praise for their work, in which they compared the incidence of postoperative clinical CME between 2 groups: 833 eyes that had femtosecond laser–assisted cataract surgery and 458 eyes that had conventional phacoemulsification. The number of cases with diabetes mellitus or retinal disease was not specified. There were 7 cases (0.8%; 4 CME cases occurred in 2 patients) of postoperative CME in the femtosecond laser–assisted cataract surgery group and 1 case (0.2%) of CME in the phacoemulsification cataract surgery group; however, there was, as they reported, no statistically significant difference between the 2 groups. In their discussion, Ewe et al.1 conclude that their findings “may be further strengthened if conducted as a randomized clinical trial or a paired-eye study.” We are pleased to bring to the authors’ and the JCRS readers’ attention that such a study exists, although it does not exactly support the notion that the incidence of CME might be significantly increased after femtosecond laser–assisted cataract surgery. Our team performed a prospective randomized controlled comparative clinical study of 104 patients.2 Each patient had traditional phacoemulsification in 1 eye and laser-assisted cataract surgery in the partner eye. Laser flare photometry was measured preoperatively and 2 hours, 3 to 4 days, and 1, 3, and 6 months postoperatively. Retinal thickness was measured by spectral-domain optical coherence tomography (OCT). The results in short: The mean center thickness in the laser group was 210 mm G 24 (SD) 4 days
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postoperatively, 214 G 22 mm at 1 month, 219 G 20 mm at 3 months, and 215 G 22 mm at 6 months. The mean center thickness in the standard group was 211 G 32 mm 4 days postoperatively, 210 G 34 mm at 1 month, 217 G 29 mm at 3 months, and 209 G 30 mm at 6 months. Laser flare photometry showed higher levels in the standard group than in the laser group at the first postoperative visit 2 hours after surgery. These results led to the conclusion that femtosecond laser–assisted cataract surgery does not obviously influence the incidence of postoperative macular edema.2 The factor most likely to cause inflammatory reactions, of which CME is one, after femtosecond laser– assisted cataract surgery seems to be the release of prostaglandins. The main trigger of the prostaglandin release is obviously the capsulotomy.3 We have shown the rise in prostaglandin levels in a couple of measurements; in 1 comparison, for instance, the aqueous humor concentration of prostaglandin E (the sample was taken after laser pretreatment and before continuing manually) was on average 19.2 pg/mL in the femtosecond laser group (n Z 20) and 4.5 pg/mL in eyes operated on conventionally (n Z 13). We came to the clinically logical, and hitherto successfully applied, conclusion that NSAIDs should be given prophylactically before laser cataract surgery.4 Another potentially prostaglandin-induced complication is the intraoperative miosis described by a number of surgeons. Time might be important in this regard: If lens removal and intraocular lens implantation immediately follow laser pretreatment, the pupil constriction hardly takes place, which seems to be an argument in favor of having the laser positioned right in the operating room5 and not in a separate laser suite, which might require a time-consuming transfer from 1 part of the hospital or practice to another. H. Burkhard Dick, MD, PhD Tim Schultz, MD Bochum, Germany Financial Disclosure: Dr. Dick is a paid consultant to Abbott Medical Optics, Inc. REFERENCES 1. Ewe SYP, Oakley CL, Abell RG, Allen PL, Vote BJ. Cystoid macular edema after femtosecond laser–assisted versus phacoemulsification cataract surgery. J Cataract Refract Surg 2015; 41:2373–2378 2. Conrad-Hengerer I, Hengerer FH, Al Juburi M, Schultz T, Dick HB. Femtosecond laser-induced macular changes and anterior segment inflammation in cataract surgery. J Refract Surg 2014; 30:222–226 3. Schultz T, Joachim SC, Stellbogen M, Dick HB. Prostaglandin release during femtosecond laser-assisted cataract surgery: main inducer. J Refract Surg 2015; 31:71–81
4. Schultz T, Joachim SC, Szuler M, Stellbogen M, Dick HB. NSAID pretreatment inhibits prostaglandin release in femtosecond laserassisted cataract surgery. J Refract Surg 2015; 31:791–794 5. Dick HB, Gerste RD. Plea for femtosecond laser pre-treatment and cataract surgery in the same room. J Cataract Refract Surg 2014; 40:499–500
Reply : We would like to thank the authors Drs. Dick and Schultz and Levitz et al. for their interest and valuable comments on our paper. As identified in both letters, we reconfirm that our study results showed no statistically significant difference in clinical CME between femtosecond laser– assisted cataract surgery and phacoemulsification cataract surgery. Either the null hypothesis is confirmed (that no causal relationship exists between femtosecond laser–assisted cataract surgery and clinical CME) as Levitz et al. suggest, or alternately, that the trend identified in our study toward a statistically significant result in favor of femtosecond laser–assisted cataract surgery being an independent risk factor causing clinical CME is rendered statistically insignificant purely because of insufficient study numbers. We disagree with Levitz et al. that evidence for the benefit of topical NSAIDs for CME prophylaxis is lacking. Although some valid limitations (as highlighted by Levitz et al.) exist with our Rossetti et al.1 reference, this was the first randomized controlled trial (RCT) to confirm a CME prophylaxis benefit from topical NSAID pretreatment to cataract surgery and hence warranted acknowledgment. Subsequent larger RCT evidence and recent metaanalyses confirm the validity of our statement that “CME is now typically less common because of prophylactic pre- and postoperative topical NSAID use combined with postoperative topical steroids.”2–4 We thank Drs. Dick and Schultz for highlighting their paired-eye study, which parallels our own published comparative cohort study findings on macular thickness.5 However, unlike our current study, both these previous study designs did not look at cases of clinical CME but rather at OCT macular thickness changes. Similarly the Tzelikis et al.6 paper referenced by Levitz et al. also did not evaluate clinical CME but only macular thickness on OCT. Small study numbers limit the ability to extrapolate conclusions about clinical CME from these OCT macular thickness studies. We also thank Drs. Dick and Schultz for highlighting their important finding regarding the more than 4-fold greater prostaglandin release after femtosecond laser–assisted cataract surgery cases compared with phacoemulsification cataract surgery, with the laser capsulotomy the likely stimulus. We agree completely with Drs. Dick and Schultz that
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