January 2019

RESIDENTS

EyeWorld journal club
Review of “A randomized controlled trial comparing femtosecond laser assisted cataract surgery vs. conventional phacoemulsification surgery”


by Karine Bojikian, MD, PhD, Shu Feng, MD, Joanne Ho, MD, and Elysse Tom, MD


Parisa Taravati, MD,
residency program director,
Department of Ophthalmology,
University of Washington


University of Washington Medicine Eye Institute ophthalmology residents, from left: Alex Solomon, MD, Mai Tsukikawa, MD, Kellie Satterfield, MD, Elysse Tom, MD, John Davis, MD, Marcela Estrada, MD, Shu Feng, MD, Gautam Vangipuram, MD, Jocelyn Lam, MD, Parker Faith, MD, Karine Duarte Bojikian, MD, Joanne Ho, MD, Brandon Erickson, MD, Ashley Roldan, MD, and Nicholas Chan, MD
Source: University of Washington

This month’s JCRS includes the largest randomized clinical trial of FLACS vs. manual phaco to date, apart from the French FEMCAT study. I invited the University of Washington residents to review this study.

—David F. Chang, MD,
EyeWorld journal club editor


Age-related cataract is the leading cause of visual impairment worldwide,1 and cataract surgery is one of the safest and most commonly performed operations worldwide.2 Phacoemulsification was first introduced more than 40 years ago and is currently the predominant surgical technique employed for cataract surgery. Each step during surgery is important, and a precise capsulorhexis is key for a successful cataract surgery, not only during the procedure itself but also for optimum long-term vision quality, as it leads to better IOL centration and less IOL tilt,3,4 which is especially important in cases of premium IOLs. Femtosecond laser platforms can be used for creation of the corneal incisions, capsulotomy and lens fragmentation. Although the potential advantages of femtosecond laser-assisted cataract surgery (FLACS) are in theory broad and include greater safety, better visual outcomes, and reduced complications through greater precision and reproducibility compared to procedures completed by hand, the evidence of the superiority of FLACS vs. conventional phacoemulsification surgery (CPS) remains controversial. A meta-analysis of 9 randomized controlled trials (RCTs) and 15 cohort studies including FLACS vs. CPS showed that FLACS appeared to be safer, faster, and achieved better visual outcomes than CPS,5 but a Cochrane meta-analysis of 16 RCTs published in 2016 could not determine the equivalence or superiority of FLACS compared to CPS due to the low to very low certainty of the evidence available from these studies.6 They argue that evidence is uncertain because current studies have not been large enough to provide a reliable answer to this question.
In “A randomized controlled trial comparing femtosecond laser assisted cataract surgery vs. conventional phacoemulsification surgery,” Roberts et al. attempt to address this question by performing a large, prospective, randomized, interventional case-controlled trial at a single center to compare the clinical results of CPS to FLACS. The study included 400 eyes of 400 patients undergoing cataract surgery, randomized to receive CPS or FLACS in equal proportions. Parameters that were measured included visual acuity (VA), refractive error, biometry by the IOLMaster 500 (Carl Zeiss Meditec, Jena, Germany), corneal topography and central corneal thickness (CCT) by Pentacam (Oculus, Wetzlar, Germany), endothelial cell count (ECC) by the Topcon SP-3000 Specular Microscope (Topcon Medical Systems, Oakland, New Jersey), and macular optical coherence tomography (OCT) by the Spectralis SD-OCT (Heidelberg Engineering, Heidelberg, Germany). Quality of life outcomes were measured with EuroQOL’s EQ-5D and patient reported quality of vision with Cat-PROM5.
Two surgeons performed the FLACS treatment using the LenSx femtosecond laser (Alcon, Forth Worth, Texas). The femtosecond laser was used to perform capsulotomy, lens fragmentation, and if needed, astigmatic keratotomies. Three surgeons performed the phacoemulsification using the Infiniti phacoemulsification machine (Alcon). An SA60AT IOL (Alcon) was placed in the capsular bag in all cases possible. Uncorrected distance visual acuity at 4 weeks was the primary outcome measure. Intra- and postoperative complications, refraction, corneal thickness, endothelial cell loss, central foveal thickness, quality of life outcomes, and patient-reported quality of vision preoperatively and at 4 weeks after surgery were selected as secondary outcome measures.
Overall, there was an astounding absence of difference in outcomes between the two groups: unaided and pinhole corrected VA (logMAR) (p=1), increase in CCT (p=0.5), ECC loss (p=0.76), refractive mean spherical equivalent error (p=0.74), change in central foveal thickness (p=0.55), mean change in Cat-PROM5 score (p=1), and mean change in EQ-5D-3L index score (p=1). Total rates of intraoperative or postoperative complications did not show a difference. Mean change in EQ-5D visual analogue scale was unchanged in the FLACS group but increased in the CPS group (p=0.02). Posterior capsular tear occurred at a significantly higher rate in the CPS group (p=0.03).
The main strength of this study is that it is the largest randomized interventional case-controlled trial designed to date comparing FLACS and CPS. The study’s follow-up of 4 weeks appears adequate for the primary outcome measure (uncorrected distance VA) given the fact that the majority of postoperative edema and inflammation tends to be resolved by this time postoperatively. Another strength was the fact that VA and any ancillary tests performed were conducted by an optometrist or technician masked to the participant’s treatment arm, which reduces detection bias. Additionally, this was the first large-scale randomized controlled trial to evaluate the rate of cystoid macular edema between FLACS and CPS, which was similar between the two arms.
The study has some limitations. (1) Lack of data regarding immediate postoperative evaluation: FLACS might have been superior in the early phase due to reduced ultrasound energy and reduced corneal edema, which translates into faster visual recovery. Additionally, cataract and glaucoma frequently coexist in the same patient and differences in early intraocular pressure (IOP) spikes may have been missed, which has an important implication in glaucoma patients’ care. (2) Surgeries were performed by only three surgeons at a single institution; these surgeons’ experience levels, patient population, and surgical preferences may not be representative of other practices. For example, their preference for segmentation pattern instead of grid pattern may have led to their finding of no difference in phacoemulsification energy between the two groups, contrary to several prior studies that have demonstrated less energy with FLACS.7–9 Additionally, while the effect of the learning curve was addressed by ensuring surgeons had completed at least 30 prior femtosecond cases, the learning curve still may have been a factor in the complication rate; it has been shown previously that complications are more likely to occur in the first 100 to 200 cases.10,11 (3) Finally, while the study is powered appropriately to detect a 0.1 logMAR VA, it is unlikely that it was large enough to effectively detect differences in relatively rare complications, such as capsular tears or suprachoroidal hemorrhages.
It should be emphasized that laser systems are expensive. The same group previously estimated that FLACS adds approximately $220 to each cataract procedure.12 Therefore, it is important to determine whether or not the increased cost associated with this procedure is mitigated by a reduction in complication rates and better patient outcomes. Studies such as this are important to further understand the role of FLACS in modern cataract surgery and ultimately help ophthalmologists choose a safe and cost-effective surgery for their patients.

References

1. Quigley HA, Broman AT. The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol. 2006;90:262–7.
2. Lawless M, Hodge C. Femtosecond laser cataract surgery: an experience from Australia. Asia Pac J Ophthalmol. 2012;1:5–10.
3. Kranitz K, et al. Femtosecond laser capsulotomy and manual continuous curvilinear capsulorrhexis parameters and their effects on intraocular lens centration. J Refract Surg. 2011;27:558–63.
4. Kranitz K, et al. Intraocular lens tilt and decentration measured by Scheimpflug camera following manual or femtosecond laser-created continuous circular capsulotomy. J Refract Surg. 2012;28:259–63.
5. Chen X, et al. Comparing the curative effects between femtosecond laser-assisted cataract surgery and conventional phacoemulsification surgery: a meta-analysis. PLoS One. 2016;11:e0152088.
6. Day AC, et al. Laser-assisted cataract surgery versus standard ultrasound phacoemulsification cataract surgery. Cochrane Database Syst Rev. 2016;7:CD010735.
7. Conrad-Hengerer I, et al. Effect of femtosecond laser fragmentation on effective phacoemulsification time in cataract surgery. J Refract Surg. 2012;28:879–83.
8. Brunin G, et al. Outcomes of femtosecond laser-assisted cataract surgery performed by surgeons-in-training. Graefes Arch Clin Exp Ophthalmol. 2017;255:805–809.
9. Yesilirmak N, et al. Differences in energy expenditure for conventional and femtosecond-assisted cataract surgery using 2 different phacoemulsification systems. J Cataract Refract Surg. 2017;43:16–21.
10. Bali SJ, et al. Early experience with the femtosecond laser for cataract surgery. Ophthalmology. 2012;119:891–9.
11. Roberts TV, et al. Surgical outcomes and safety of femtosecond laser cataract surgery: a prospective study of 1500 consecutive cases. Ophthalmology. 2013;120:227–33.
12. Roberts HW, et al. Financial modelling of femtosecond laser-assisted cataract surgery within the National Health Service using a ‘hub and spoke’ model for the delivery of high-volume cataract surgery. BMJ Open. 2017;7:e013616.

Contact information

Taravati
: taravati@uw.edu

Review of “A randomized controlled trial comparing femtosecond laser assisted cataract surgery vs. conventional phacoemulsification surgery” Review of “A randomized controlled trial comparing femtosecond laser assisted cataract surgery vs.
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