Management of the capsulorrhexis is a fundamental step in cataract surgery. When the rhexis is too large or too tight or when a tear develops, complications can emerge during subsequent surgical stages. The best capsulorrhexes are round, continuous, well centered, and overlapping the edge of the IOL around its circumference. If one of these elements is missing, it can often become a barrier to optimal surgical outcomes. In such cases, set strategies should be employed to reverse the effects of the defective continuous curvilinear capsulorrhexis (CCC) and save the procedure.
The most devastating capsulorrhexis complication is the errant capsular tear. This can happen any time that centrifugal traction forces overcome the centripetal forces applied by the surgeon on the capsular flap. To understand this concept, we must first identify the two forces that influence the direction of the capsular flap. One is transmitted to the external border of the rhexis by the tension of the zonular fibers and is proportional to the convexity of the anterior capsule. This force pushes outward. The surgeon transmits a second, inward force as he or she pulls on the capsular flap. The balance of these two forces determines the direction of the capsulotomy (Figure 1). Therefore, a rupture is more likely to occur when centrifugal forces are increased due to a highly convex anterior capsule.
When a rupture extends to the lens equator (Figure 2), the first step is to refill the anterior chamber with an ophthalmic viscosurgical device (OVD) to relieve zonular tension and create better control of the tear. To assist with this maneuver, it is helpful to press on the nucleus in the area where the anterior capsule has been removed. This can be accomplished by using a spatula inserted through a sideport incision. A cohesive OVD will flatten the anterior capsule better than a dispersive OVD, but a dispersive will remain inside the anterior chamber longer. Therefore, a technique that uses both OVDs, such as the Arshinoff soft-shell technique, is often the best solution in these cases.
REDIRECTING THE CAPSULORRHEXIS BORDER
If a tear begins to travel toward the equator, capsulorrhexis forceps can be used to change its direction. The surgeon should grasp the flap as near to the base as possible and pull it toward the center of the pupil. The farther one’s grip is from the base of the flap, the more difficult it is to redirect the flap. Therefore, the surgeon must continually regrasp the flap closer to its base as the capsulotomy continues.
If the tear extends peripherally under the iris, where it is impossible to visualize and control, another CCC should be initiated. This new CCC should be started in the opposite direction from the cut or puncture made to begin the original CCC. If there is no cut or puncture available at the original site, a new tag should be created with a cystotome and the rhexis completed to the point where it was abandoned.
Capsulorrhexis tears occur more frequently when the anterior capsule is highly convex, such as in hyperopic patients or in the presence of intraoperative shallowing of the anterior chamber due to surgeon errors such as an over-sized incision or excessive instrument pressure. Additionally, peripheral extension of the rhexis tear is more frequent in pediatric cases due to higher capsular elasticity and in patients with intumescent (Figure 3) or hypermature cataract due to intracapsular fluid pressure.
MANAGING THE TEAR
When a radial tear occurs before phacoemulsification, surgery can still be completed as planned, using care to avoid progression to a posterior rupture. Gentle hydrodissection should be performed on the side opposite from the tear, avoiding rotation to minimize capsular stress. Even more important is to perform an accurate hydrodelineation to completely detach the nucleus from the cortical shell.
Once the nucleus is detached, phaco can be completed using increased phaco power and decreased fluidics parameters. Chopping techniques are more suitable than nucleus fracture techniques in these cases, as they reduce stress on the capsule. Alternatively, in some cases, it is safer to remove the nucleus from the capsular bag and chop it in the anterior chamber. Regardless of the chosen technique, it is important to minimize manipulations to avoid transmitting excessive force to the rhexis border, and not to over-inflate the capsular bag with OVD. With a foldable one-piece acrylic IOL, which will open gently inside the capsular bag, it is almost always safe to implant the lens at the conclusion of surgery in these eyes.
In the rare case in which the tear has extended to the posterior capsule, conversion to extracapsular cataract extraction is acceptable, especially if the surgeon does not have great expertise managing capsular complications.
CCCs with incorrect dimensions can create problems in subsequent surgical steps, from nucleus emulsification to cortex removal. An oversized rhexis can cause the nucleus to move forward and herniate into the anterior chamber, complicating hydrodissection and phacoemulsification.
A CCC that is too large and does not cover the edge of the IOL can increase the risk for posterior capsular opacification due to proliferation and migration of lens epithelial cells; it can also result in dysphotopsias including glare, halos, and ghost images.
On the other hand, an undersized rhexis also creates problems, increasing the difficulty of all subsequent surgical maneuvers such as nucleus management and cortex removal. Proliferation of lens epithelial cells postoperatively can lead to an inflammatory reaction causing capsular phimosis and opacification. In eyes with weak zonules, lens movement and rhexis phimosis can occur (Figure 4). In such cases, it is advised to enlarge the opening by performing a second, wider rhexis to eliminate the risk for stenosis of the opening. To achieve this, after refilling the anterior chamber with an OVD, a new tag should be created in the rhexis border using a cystotome or scissors. Forceps can then be used to create the new, larger capsulotomy. If the rhexis is small but not so small as to create surgical difficulties, one can wait until the end of surgery to remodel the CCC using the same technique. This provides greater safety due to the support created by the IOL plate.
Execution of a perfect rhexis is a fundamental step in cataract surgery. Until recently, this is the only step in the procedure that was not influenced by technological improvement, as only a needle or forceps were required to create the CCC.
Today, however, it is possible to use a femtosecond laser for this surgical step. It appears that these lasers can perform the CCC not only with safety and accuracy in terms of diameter, position, and continuity, but also with refractive precision. This innovation will be particularly suitable in complex cases such as pediatric patients and those with pseudoexfoliation syndrome or intumescent cataract.
Alessandro Franchini, MD, is a Professor at the School of Ophthalmological Specialization, University of Florence, Italy. Dr. Franchini states that he has no financial interest in the companies or products mentioned. He may be reached at e-mail: alessandrofranchini@ yahoo.it.