Can a manual capsulotomy be as effective as a laser-assisted capsulotomy during cataract surgery?

Issue: July 10, 2018

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A perfect capsulotomy

With femtosecond laser-assisted cataract surgery now, my answer is no. Even in routine cases, we observe a shift of the pupil center with dilation, so centration is never perfect with manual capsulotomy. With femtosecond lasers, we have the option to change the centration, and it is very precise. I always use the scanned capsule centration when possible. There are cases in which there is no question a perfect capsulotomy is key for the success of the surgery, such as patients with traumatic cataracts and zonular dehiscence, for example, or patients with lens subluxation, because the entire capsular bag is decentered to start with, with poor zonular support. In these cases it is very hard to center the capsulotomy on the dislocated capsular bag.

With image-guided femtosecond lasers, you can scan the entire anterior capsule and then adjust your centration. It makes surgery much easier when you need to use capsule retractors, capsular tension rings or even sutured Ahmed segments. In these cases, femtosecond laser-assisted capsulotomy really helps.

We recently made some changes to optimize our capsulotomy settings: We changed the vertical spot spacing from 10 µm to 15 µm and the spiral (incision depth) to 400 µm instead of 600 µm. Pulse energy is usually 4 µJ, and horizontal spot spacing is 5 µm. Using these settings, the femtosecond laser creates a capsulotomy in 0.7 seconds. Intraoperatively, this is beneficial in high hyperopes with shallow anterior chambers in hypermature cataract cases.

Previous studies have shown elevated prostaglandin levels in the aqueous humor immediately after femtosecond laser-assisted cataract surgery and identified them as a potential mediator for laser-induced miosis. Optimizing energy settings by reducing the incision depth and lowering the pulse energy in combination with nonsteroidal anti-inflammatory pretreatment prevents prostaglandin release and reduces the phenomenon of laser-induced miosis.

References:
Jun JH, et al. J Cataract Refract Surg. 2017;doi:10.1016/j.jcrs.2017.01.011.
Schultz T, et al. J Refract Surg. 2015;doi:10.3928/1081597X-20151111-01.
Schultz T, et al. J Refract Surg. 2015;doi:10.3928/1081597X-20150122-01.

Karolinne M. Rocha, MD, PhD, is a member of the faculty at Medical University of South Carolina, Storm Eye Institute. Disclosure: Rocha reports she is a consultant for Johnson & Johnson.

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More accurate and reproducible

Femtosecond laser cataract surgery is capable of assisting or completely replacing several crucial aspects of the cataract surgical procedure, including clear corneal incisions, creation of capsulotomy, fragmentation, and astigmatic correction both through arcuate incisions and toric IOL steep axis marks. While these may seem to be small incremental improvements, collectively these can bring substantial benefits to patients undergoing FLACS.

A capsulorrhexis created with FLACS has been found to be more accurate and reproducible in terms of intended diameter, circularity and centration, ensuring better IOL overlap and minimizing the chances of IOL tilt and decentration, than manual continuous-tear curvilinear capsulorrhexis. It yields a postoperative IOL position that is more predictive. As a natural consequence, IOL power calculations are more predictive, lowering mean absolute error. Conrad-Hengerer and colleagues showed a greater percentage of patients achieving postoperative refraction within ±0.5 D of the target at 6 months postoperatively (91% vs. 71% for FLACS and manual, respectively). FLACS-assisted astigmatism correction by arcuate incision construction during cataract surgery is a safe and effective treatment option.

At the American Society of Cataract and Refractive Surgery 2016 annual meeting, I presented data on 52 eyes of 31 patients with pre-existing astigmatism ranging between 0.4 D to 2.75 D. There was a significant reduction in the mean absolute value of refractive astigmatism from 1.3 D to 0.3 D (P < .001). Visco and Weinstock studied FLACS-assisted steep axis corneal marks followed by toric IOL implantation. Seventy-three eyes were enrolled in the study with a mean preoperative corneal cylinder of 2.23 D ± 0.19 D (range, 1.15 D to 4.5 D). At 1 month, 93.2% of eyes achieved 0.5 D or less and 76.7% of eyes achieved 0.25 D or less residual refractive astigmatism. The mean residual refractive astigmatism was 0.19 D ± 0.38 D. These results compare favorably with other studies of toric IOL implantation. While better uncorrected distance visual acuity outcomes are expected, Kránitz and colleagues reported significantly better corrected distance visual acuity 1 year after FLACS (P = .038) due to lower induction of higher-order aberrations, significantly higher Strehl ratios and modulation transfer function values in the laser group compared with the manual group. Femtosecond laser-assisted pre-fragmentation of the crystalline lens lowers the effective phacoemulsification time and energy, translating into less corneal endothelium damage, corneal edema/central corneal thickness and aqueous flare compared with the manual procedure. The overall complication rate with FLACS has also been reported to be lower (1.8%) than manual (5.8%).

References:
Abell RG, et al. Clin Exp Ophthalmol. 2013;doi:10.1111/ceo.12025.
Abell RG, et al. J Cataract Refract Surg. 2013;doi:10.1016/j.jcrs.2013.06.009.
Abell RG, et al. J Cataract Refract Surg. 2014;doi:10.1016/j.jcrs.2014.05.031.
Abell RG, et al. Ophthalmology. 2013;doi:10.1016/j.ophtha.2012.11.045.
Chen M, et al. Int J Ophthalmol. 2015;doi:10.3980/j.issn.2222-3959.2015.01.34.
Conrad-Hengerer I, et al. J Cataract Refract Surg. 2013;doi:10.1016/j.jcrs.2013.05.033.
Conrad-Hengerer I, et al. J Cataract Refract Surg. 2015;doi:10.1016/j.jcrs.2014.10.044.
Conrad-Hengerer I, et al. J Refract Surg. 2012;doi:10.3928/1081597X-20121116-02.
Daya SM, et al. J Cataract Refract Surg. 2014;doi:10.1016/j.jcrs.2013.07.040.
Jackson MA. Treatment of corneal astigmatism using femtosecond laser–assisted arcuate incisions during cataract surgery. Presented at: American Society of Cataract and Refractive Surgery meeting; May 7-10, 2016; New Orleans.
Kránitz K, et al. J Refract Surg. 2012;doi:10.3928/1081597X-20120309-01.
Mayer WJ, et al. Am J Ophthalmol. 2014;doi:10.1016/j.ajo.2013.09.017.
Mihaltz K, et al. J Refract Surg. 2011;doi:10.3928/1081597X-20110913-01.
Popovic M, et al. Ophthalmology. 2016;doi:10.1016/j.ophtha.2016.07.005.
Reddy KP, et al. J Cataract Refract Surg. 2013;doi:10.1016/j.jcrs.2013.05.035.
Toto L, et al. J Refract Surg. 2015;doi:10.3928/1081597X-20150727-02.
Visco DM, et al. Astigmatism management using steep-axis corneal landmarks created with a femtosecond laser: multicenter prospective clinical study. Presented at: American Society of Cataract and Refractive Surgery meeting; May 7-10, 2016; New Orleans.

Mitchell A. Jackson, MD, is an OSN Refractive Surgery Board Member. Disclosure: Jackson reports he is a consultant for Lensar and Bausch + Lomb.

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Producing a precise rhexis

Cataract surgeons first began using femtosecond lasers in 2010, and since then there has been an increase in utilization of this technology. Femtosecond lasers in cataract surgery play an important role in the formation of the anterior capsulotomy, lens fragmentation and astigmatism correction. Recent publications comparing laser-assisted and conventional cataract surgery concerning the capsulotomy have investigated several indicators of outcome, namely IOL tilt, anterior capsular tears, capsulotomy diameters and circularity.

Creation of the anterior capsulorrhexis is a key component in the success of cataract surgery. Producing a precise rhexis is a key step in achieving favorable visual outcomes and avoiding complications. By nature, manual compared with laser-assisted capsulotomies will have more frequent inconsistencies in the curvature of the rhexis. In 2012, Nagy and colleagues noted that 28% of manual capsulotomies had incomplete overlap of the capsule-lens interface as opposed to 11% with laser-assisted capsulotomy (P = .033). Furthermore, in a meta-analysis, Qian and colleagues noted that laser-assisted cataract surgery had a more significant advantage than manual capsulotomy in creating circular capsulotomies (MD = 0.09; 95% CI, 0.05 to 0.12, P < .0001).

Regarding visual outcomes, two studies by Kránitz and colleagues and Nagy and colleagues reported significant correlations between increased IOL tilt and decentration after manual capsulotomy. The inability to create consistent, circular and overlapping capsulotomies can theoretically affect visual outcomes and result in an increase in higher-order aberrations and internal astigmatism. However, there have been varying reports in the literature concerning refractive outcomes of manual vs. femtosecond laser — some showing manual better and others showing femto better.

Depending on the skill of a surgeon, manual capsulotomy can be as effective as laser-assisted capsulotomy with regard to visual outcomes; however, achieving consistently circular and centered capsulotomies with precise IOL overlap is more challenging manually. There is a need for prospective studies comparing long-term refractive outcomes in manual vs. femtosecond cases, especially in complicated cataracts and premium lenses.

References:
Ewe SYP, et al. Ophthalmology. 2016;doi:10.1016/j.ophtha.2015.09.026.
Kránitz K, et al. J Refract Surg. 2012;doi:10.3928/1081597X-20120309-01.
Manning S, et al. J Cataract Refract Surg. 2016;doi:10.1016/j.jcrs.2016.10.013.
Nagy ZZ, et al. J Refract Surg. 2011;doi:10.3928/1081597X-20110607-01.
Qian D-W, et al. Int J Ophthalmol. 2016;doi:10.18240/ijo.2016.03.23.

Zaina Al-Mohtaseb, MD, is an ophthalmologist with the department of ophthalmology at Baylor College of Medicine, Houston. Disclosure: Al-Mohtaseb reports she is a consultant to Alcon and Bausch + Lomb and receives research funding from Johnson & Johnson.