Creating a continuous curvilinear capsulorrhexis (CCC) is perhaps the most crucial—and the most delicate—step of cataract surgery. The CCC is typically completed safely and appropriately; however, when a complication arises, a wellplanned approach can avoid further harm to the eye. This article reviews several common complications of the CCC and suggests plans for their resolution.
ECCENTRIC RHEXIS AND RADIAL TEARS
Rhexis moving out. A rhexis traveling toward the periphery of the anterior capsule is dangerously close to causing a radial tear. The capsulorrhexis can usually be saved with a simple maneuver (see Rescuing a Capsulorrhexis Tear-Out); however, chances are that the resulting CCC may not overlap with the IOL’s optic. If the rhexis cannot be completed, this may be a precursor for posterior capsular rupture, especially in patients with an intumescent cataract.
Using a highly cohesive ophthalmic viscosurgical device (OVD) to fill the anterior chamber and flatten the anterior capsule, along with relieving some of the intracapsular pressure by aspirating liquefied cortical material after opening the capsule, usually counteracts the centrifugal vector and makes a tear-out less likely.
Radial tear. Radial tears during CCC usually occur because pressure is applied to the wound lip, allowing too much OVD to flow out of the eye and causing the anterior chamber to shallow. Once this occurs, the vector force of the tear shifts toward the periphery of the lens, pushing or pulling the rhexis flap in that direction. If the surgeon has difficulty controlling the capsulorrhexis, a radial tear can result. The logical solution in these cases is to convert to a can-opener technique, using a needle to create small cuts in the capsule. The drawback to a can-opener capsulotomy is that, with the possibility of several radial tears extending into the periphery, postoperative visual results can be poor.
A radial tear can also occur during phacoemulsification, when a sharp instrument or a vibrating phaco tip touches the edge of the capsulorrhexis. It may still be safe to complete phacoemulsification, but minimal stress should be applied to the capsule to avoid extension of the tear onto the posterior capsule. The use of slow, controlled movements to chop or divide the lens can avoid the extension of the capsulorrhexis into the periphery. When I feel that there is a lot of stress being exerted on a radial tear, I may create one or two relaxing incisions in the anterior capsule at other positions to reduce the strain on the existing tear.
A typical capsulorrhexis. The CCC should be between 5.0 and 5.5 mm in diameter.
A large rhexis. If the CCC is larger than the optic of the IOL, decentration and/or tilt can result. This occurred frequently with older silicone plate-haptic lenses; however, even with modern IOLs, there is a higher tendency for invasion of lens epithelial cells and, subsequently, posterior capsular opacification, in the region with no overlap of the optic and the capsulorrhexis.
A small rhexis. If the rhexis is too small, there is a higher likelihood of contraction or complete closure (ie, rhexis phimosis) of the CCC. In such cases, Nd:YAG capsulotomy can be performed to open the capsulorrhexis. In severe cases, it may be necessary to surgically remove the whitened and contracted capsule. Even if capsulorrhexis contraction is not severe, this may result in a poor view of the peripheral retina.
Make sure the CCC is centered, round, and properly sized. In most cases, this means that the diameter of the capsulorrhexis is between 5.0 and 5.5 mm. Pupil size can be misleading, however. For instance, it is easy to be misled and make the capsulorrhexis too large if the eye is myopic and the pupil is maximally dilated. Likewise, it is easy to make the capsulorrhexis too small if the eye has a smaller or poorly dilated pupil.
There are several techniques to aid in sizing the rhexis. For instance, a circular corneal marker with a diameter of 5.0 mm can be used to create a weak imprint on the corneal epithelium to help guide the rhexis. However, the magnification factor of the cornea as well as parallax when tilting the eye during the procedure may still result in small deviations in size. A more high-tech approach is the use of a microscope that tracks the limbus of the eye during surgery and superimposes a circular line onto the live image in one of the surgeon’s eyepieces (Callisto; Carl Zeiss Meditec AG; Figure 1). We have completed a trial with such a microscope set-up and were able to show that the achieved rhexis diameters were within 0.2 mm of the planned size (Figure 2).1
QUESTIONS FOR A NEW ERA
The advent of laser cataract surgery introduces a new level of precision into this already safe and efficient procedure. Many surgeons and industry representatives suggest that using the femtosecond laser to create a CCC will result in better IOL centration and more reliable refractive outcomes. The concept, they say, is that perfect overlap of the capsulorrhexis with the optic will result in less capsular shrinkage and more predictable anterior-posterior axial position of the IOL optic.
However, my colleagues and I have conducted several trials in the past looking at IOL position after conventional cataract surgery as measured with laser interferometry of the anterior segment to assess axial position. We also used a Purkinje meter, a prototype designed by Pablo S. Artal, MD, of Spain,2 to assess optic decentration and tilt. In these studies, we measured the axial position of the IOL immediately postoperatively and during the typical time of capsular contraction (3 to 6 months after surgery), and we concluded that not only do modern lenses shift very little in this time but there is no good correlation between axial position and rhexis size.
Using these studies as my reasoning, I do not think that laser cataract surgery will have a large impact on axial position and, therefore, refractive outcome, or on IOL centration and tilt with modern hydrophobic or hydrophilic acrylic IOLs with haptics of high memory. It may, however, hold true for old-fashioned lenses with rounded edges as well as for PMMA or silicone lenses, with which the fibrosis was usually stronger. It will be interesting to see good data from randomized, controlled trials comparing laser capsulorrhexis with manual capsulorrhexis to see if there really is a difference with these parameters.
For the veteran surgeon, complications of the CCC are rare but nevertheless challenging. The keys to successfully managing these cases include the following pointers: Make sure the anterior chamber is completely filled with OVD during the entire capsulorrhexis procedure. As soon as the capsulorrhexis becomes uncontrolled, double check that there is adequate pressure in the anterior chamber and refill it with OVD to ensure that the chamber is once again deep. When this has been done, it is probably safe to proceed with surgery. As always, using common sense and a well-thought-out surgical technique is recommended.
Oliver Findl, MD, MBA, is Director of Ophthalmology at the Hanusch Hospital, Vienna, Austria, and a Consultant Ophthalmic Surgeon at Moorfields Eye Hospital, London. He is also the Head of the Vienna Institute of Research in Ocular Surgery, Hanusch Hospital, Department of Ophthalmology, Vienna, Austria. Dr. Findl states that he has no financial interests in the products or companies mentioned. He may be reached at e-mail: email@example.com.
- Findl O. Intraoperative alignment of IOL and control of rhexis size using a modified operating microscope. Paper presented at the: XXIX Congress of the ESCRS; September 20, 2011; September Vienna, Austria.
- Nishi Y, Hirnschall N, Crnej A, et al. Reproducibility of intraocular lens decentration and tilt measurement using a clinical Purkinje meter. J Cataract Refract Surg. 2010;36(9):1529-1535.