BLOG: Centration in femtosecond laser procedures
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Femtosecond lasers offer us the opportunity to create a fast, centered capsulotomy more effectively than is possible in a manual procedure.
The Catalys femtosecond laser (Johnson & Johnson Vision) allows surgeons to choose from five different centration methods: pupil, pupil maximized, limbus, scanned capsule or a custom setting.
I use the “scanned capsule” centration method in all refractive cases, including multifocal IOLs, toric IOLs, monofocal IOLs with laser astigmatism management, and post-myopic LASIK cases that are implanted with a negative spherical aberration IOL. The laser maps the capsular surfaces based on the integrated OCT imaging and identifies the center of the capsule. The idea with this centration method is that, because the IOL haptics naturally center the implant within the anatomical dimensions of the capsule, we would want the capsular opening to be symmetrically aligned with the IOL below it. Lee and Joo reported that the scanned capsule center is significantly closer to the IOL center than either the pupil center or limbal center.
In 2013, Wiley and colleagues compared scanned capsule and pupil centration and found that scanned capsule resulted in a better position in 82% of eyes, with no difference in an additional 9%. All of the scanned capsule eyes had 360° optic overlap by the capsule compared with only 75% of the eyes with pupil-centered capsulotomies. Optic overlap is important to reduce tilt and decentration by ensuring circumferentially equal force on the capsule as it fibroses and the lens settles into its final position. Nagy and colleagues also reported fewer cases of incomplete capsule overlap and a lower rate of IOL decentration in FLACS eyes compared with manual capsulorrhexis eyes.
While I use the scanned capsule setting in the vast majority of my FLACS cases, there are some unique situations when I prefer the “pupil maximized” setting. For example, in an eye with a small pupil, when I have to manually adjust the pupil size overlay, I find that pupil maximized centration will allow me to achieve a larger capsular opening. I also use this setting in eyes with dense, mature cataracts, when I want a larger capsulotomy (5.5 mm to 6 mm) to facilitate the phaco portion of the procedure. Finally, in the presence of Intacs corneal ring segments (Addition Technology) or an ICL (STAAR Surgical), the maximized setting allows me to manually place the capsulotomy where I want it to avoid the implants.
From my experience, advanced capsule imaging and laser capsulotomy settings are critical for both refractive cataract surgery and getting through complex cases.
References:
- Kránitz K, et al. J Refract Surg. 2011;doi:10.3928/1081597X-20110623-03.
- Lee YE, et al. Invest Ophthalmol Vis Sci. 2015;doi:10.1167/iovs.15-17454.
- Nagy ZZ, et al. J Refract Surg. 2011;doi:10.3928/1081597X-20110607-01.
- Wiley WF, et al. Optical coherence tomography guided capsule bag-centered femtosecond laser capsulotomy. Presented at: American Society of Cataract and Refractive Surgery annual meeting; April 20, 2013; San Francisco.
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