Small increase in capsulorrhexis diameter makes big difference in cataract surgery
This will dramatically increase the area of the opening and help match the capsulorrhexis to the IOL optic size.
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The capsulorrhexis is a critical step of cataract surgery because it provides access to the lens material and then securely holds the IOL.
The advantage of a tearing a continuous curvilinear capsulorrhexis is that it is strong and resists ripping because there are no weak spots. We also want the capsulorrhexis to overlap the optic edge of the IOL in order to provide long-term stability and a more predictable effective lens position, both of which are important for restoring vision to our patients.
Most of the commonly used IOLs have a single optic that is designed to be fixed and nonmobile within the capsular bag. These IOLs have a 6-mm optic diameter, and thus to achieve overlap by the capsule for stability, the capsulorrhexis should have a 5- or 5.5-mm diameter. While a smaller 4-mm capsulorrhexis will also provide good IOL optic overlap and stability, the smaller size makes the removal of the cataract more challenging.
In the case shown here, the patient has a dense brunescent cataract with 4+ nuclear sclerosis. The imaging showed a cataract of 9.5 mm in diameter with a lens thickness of 4.7 mm. The capsule was stained with trypan blue dye, and a capsulorrhexis was completed, ending up with a diameter of 4 mm. Removing this large and dense nucleus through a smaller opening like this will be a challenge.
To remove a large nucleus through a smaller capsulorrhexis, it will need to be subdivided into smaller segments. A helpful technique is to debulk the central nucleus using a wide and deep groove so that once the remaining halves are split, they each represent about 40% of the nucleus volume. If we just chop the nucleus into two halves without any central sculpting, each hemi-nuclear piece will be 50% of the nucleus volume. These hemi-nuclear halves will need to be further chopped into smaller segments for easier removal through the small capsulorrhexis.
Source: Uday Devgan, MD
This 4-mm capsulorrhexis has an area of about 12.5 mm2, but if we enlarge the capsulorrhexis to 5 mm, then the area increases to 19.6 mm2, which is an increase of 56% (Figure 1). A 5.5-mm capsulorrhexis gives an opening of 23.7 mm2, which is nearly double the area of the 4-mm capsulorrhexis. This allows much more room for nucleus removal during phaco. We can then stick with our chop technique without having to debulk the central endonucleus.
Once we create a small capsulorrhexis, we are not stuck with this limited size because we can safely and easily enlarge it. This is done at the beginning of the surgery while the anterior chamber is still filled with viscoelastic. Small Vannas scissors are used to incise the capsulorrhexis edge, being careful to do so tangentially and not radially (Figure 2).
This small flap of the anterior capsule is then grabbed using capsulorrhexis forceps, and a spiral tearing technique is used to enlarge the opening. Once the desired capsulorrhexis size is reached, the additional tear can be terminated by bringing it centrally. This results in an intact and continuous capsular opening that is as strong as the original capsulorrhexis. Now with a larger opening, the disassembly or removal of the nuclear pieces will be easier.
At the end of the surgery, the IOL is placed in the capsular bag, and we see that there is an ideal overlap of the optic edge by the capsulorrhexis. If needed, we can further enlarge the capsulorrhexis once the IOL is inserted and the eye is still filled with viscoelastic.
The capsulorrhexis is a critical part of successful cataract surgery, and creating an ideal-sized opening can be done initially or by enlarging a smaller than desired one. A small increase in the capsulorrhexis diameter will increase the area of the opening dramatically. And when we match the capsulorrhexis to the IOL optic size, we can ensure long-term stability and a more precise refractive outcome for our patients.
Surgical video of this case is available on CataractCoach.com.
- For more information:
- Uday Devgan, MD, is in private practice at Devgan Eye Surgery, Chief of Ophthalmology at Olive View UCLA Medical Center and Clinical Professor of Ophthalmology at the Jules Stein Eye Institute, UCLA School of Medicine. He can be reached at 11600 Wilshire Blvd. #200, Los Angeles, CA 90025; email: devgan@gmail.com; website: www.CataractCoach.com.
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