December 24, 2015
4 min read

Femtosecond laser allows fine-tuning of capsulotomy size

Carlos Buznego, MD, and Jennifer Loh, MD, discuss the pros and cons of smaller vs. larger capsulotomies.

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Welcome to another edition of CEDARS/ASPENS Debates. CEDARS/ASPENS is a joint society of cornea, cataract and refractive surgery specialists, here to discuss some of the latest hot topics in ophthalmology.

As more surgeons have access to femtosecond laser technology for cataract surgery, we are now able to fine-tune our procedure in ways we never thought possible. One area is the capsulotomy. While we have long understood the importance of a circular and well-centered capsulotomy, we now are able to discuss the importance of fractions of a millimeter when it comes to capsulotomy size. Twenty years ago, this discussion would have seemed irrelevant, but now, we are able to see how much more precision we have gained in our technique to allow patients to achieve the best outcomes possible.

This month, Carlos Buznego, MD, and Jennifer Loh, MD, discuss the merits of adjusting the capsulotomy size. We hope you enjoy the discussion.

Kenneth A. Beckman, MD, FACS

Laser capsulorrhexis: How small is too small?

The femtosecond laser has provided ophthalmic surgeons with an incredibly precise instrument to facilitate cataract surgery. However, surgeons are sometimes faced with uncertainty as how to best utilize this powerful new tool.

Carlos Buznego

Laser capsulotomy is among the most important uses of the femto laser. A well-formed capsulorrhexis is widely accepted as the most important step in successful cataract surgery. A perfectly formed and centered rhexis maximizes the strength of the capsular bag, minimizes posterior capsule opacification and facilitates consistent effective lens position.

Some early experience with laser capsulotomy suggested that a rhexis diameter of less than 5 mm was associated with weakened tensile strength and increased risk of capsular breakage. Anatomical studies suggested that the maximal thickness of the anterior capsule is seen at diameters of 4.9 mm to 5.5 mm. In addition, Packer and colleagues found that capsulorrhexis strength was statistically stronger in a 5.5-mm capsulorrhexis compared with a 4-mm capsulorrhexis. These factors have contributed to the widespread acceptance of a 5- to 5.5-mm capsulorrhexis by the majority of femto laser cataract surgeons.

However, how should we manage patients with poorly dilating pupils? This can be a relatively large proportion of our cataract patients. Risk factors for pupillary miosis include pseudoexfoliation, alpha blocker usage, diabetes, glaucoma, uveitis and prior trauma. Should we simply defer to manual capsulorrhexis? Should we utilize a device to expand the pupil and proceed with femto laser capsulorrhexis and re-dock an “open” eye? Or can we perform femto laser capsulorrhexis in patients with suboptimal pupil size?

Our center has had good experience utilizing femto laser capsulorrhexis in patients with dilated pupils of less than 5 mm. Trattler and colleagues reported a series of 39 cases of small-diameter capsulorrhexes performed by seven different surgeons utilizing the same Lensar laser. Patients in this series had femto laser capsulorrhexis performed with diameters ranging from 3.9 mm to 4.9 mm. The limited series showed successful and uncomplicated cataract surgeries in all of the patients.

Our experience confirms that when performed with caution, femto laser capsulorrhexis can be utilized for cataract surgery patients with dilated pupils under 5 mm in diameter. In fact, these patients who are at higher risk for surgical complications benefit from the consistency of the perfectly formed capsulorrhexis and the laser nuclear fragmentation that follows.

Disclosure: Buznego reports he is a consultant to Lensar.


Femtosecond laser cataract surgeries: Is bigger really better?

Femtosecond laser cataract surgery has been developed to help make some of the early steps in cataract surgery automated and reproducible. The goal is to reduce risk as well as help provide more consistent outcomes. While there is debate as to the merits of femtosecond incisions, there is little debate that a centered, round capsulotomy is an important feature of femtosecond laser cataract surgery. The goal of the centered capsulotomy is to help ensure that there is a “perfect” capsulotomy with each procedure, and by centering the capsulotomy, the goal is to provide a framework for the IOL, whether monofocal, toric or presbyopic, to provide the best quality of vision. This is achieved with overlap of the capsulotomy over the edge of the optic.

Jennifer Loh

When considering the size of the capsulotomy, there are advantages and disadvantages for smaller vs. larger capsulotomies. Because the typical optic is 6 mm in diameter, creating a capsulotomy that is 5 mm or smaller will have an increased chance of having the edge of the optic covered by the capsulotomy 360°. This will help keep the IOL in a planar position and prevent tilt. The downside of smaller capsulotomies is that it makes later steps in cataract surgery slightly more challenging, especially in more advanced cataracts. In contrast, larger capsulotomies make the later steps in cataract surgery just a little bit easier, from nuclear disassembly to cortex removal. However, if the capsulotomy is too big or not centered, there may not be good capsule overlap of the optic.

With these thoughts in mind, I have selected a 5.3-mm capsulotomy size for my procedures. I based this decision on work performed by Packer and colleagues, in which he found that the capsule is strongest at 5.5 mm by evaluating the tensile strength on porcine eyes comparing different size laser capsulotomies and manual capsulotomies. His study showed that with increasing size, up to the 5.5 mm diameter studied, the capsulotomy was increasingly resistant to breakage. He concluded, however, that by reducing the capsulotomy size slightly to 5.25 mm, there would be advantages in both capsulotomy strength and an ideal overlap of the optic.

My personal experience has found that 5.3 mm is ideal in terms of ease of removing lens fragments and removing the cortex, which can be more difficult during femtosecond laser cases. While many argue that a smaller capsulotomy can suffice, I believe that we should utilize femtosecond laser technology to create the size that is ideal for the patient and also allows the surgeon to have the most stress-free experience possible, thereby reducing our complication rate and maximizing the patient experience.

Disclosure: Loh reports no relevant financial disclosures.