IV. PITFALLS AND HOW TO AVOID THEM
The hardest part of cataract surgery for the beginning surgeon is mak- ing a consistently good capsulorrhexis. Frequent practice is important for improving. For those who have access, the Eyesi Surgical simulator for cataract (VRmagic Holding AG) is an excellent surgical simulator for practicing capsulorrhexis. In this section, I will review a few common capsulorrhexis pitfalls and offer my advice for dealing with them.
- A capsulorrhexis can always be made larger, but it can never be made smaller. It is important to make the initial capsule puncture and tear small and central, and then spiral it out to the desired diameter. If the initial capsule tear goes wide, the entire capsulorrhexis will be larger than necessary. A capsulorrhexis that overlaps the edge of the optic for 360 degrees is optimal for retarding posterior capsule opacification. Tight adhesion of the anterior and posterior capsule leaflets impedes migration of lens epithelial cells behind the optic. A capsulorrhexis that overlaps the optic 360 degrees also makes it safer when it comes time to make a circular Nd:YAG laser posterior capsulotomy opening. When the anterior capsulotomy goes wide of the optic, vitreous will occasionally migrate around the edge of the optic into the anterior chamber.
- The most common problem experienced by beginning surgeons is outward radialization of the capsulorrhexis. The trick is to recognize the impending problem before the tear extends too far peripherally. The common beginner mistake is to pull the flap radially in toward the center of the pupil when the radialization begins to happen, as though one were swinging a rock in the circle at the end of a rope. Pulling the capsule flap centrally converts the shearing tear into a ripping tear. Ripping is inherently less controlled. The capsule tends to run radially outward when it is ripped.
- The first thing a surgeon should do when the capsulorrhexis begins to extend peripherally is stop and inject more OVD to flatten the anterior dome of the lens. Then the capsule should be flopped over so that it aligns with the tangent of the intended circle. Sometimes it is necessary to tear the capsule outwardly a little bit before it can be brought around. If the capsulorrhexis goes out beneath the pupil, the surgeon can continue the tear as long as he or she has a sense of where it is going. Sometimes it is useful to introduce a Kuglen iris push- pull hook to push the pupil back and visualize the tear as it is being redirected. If control cannot be achieved at the tear site, the surgeon should stop. Indiscriminate pulling on the capsule flap will cause the tear to go posteriorly through the zonules and around the backside of the lens. Capsulorrhexis rescue techniques described in Section VI (p. 94) should be used at this point. Alternatively, the surgeon can puncture the capsule again with a 30-gauge needle and tear it in the reverse direction. The 2 tears can be joined at the point where the initial tear went wide.
- Another common problem is difficulty visualizing the capsule. This occurs most often when a tear proceeds over an area where white cortical material is present. The key here is good focus and magnification. Before capsule stains were available, all surgeons had to confront this problem head-on. It helps to avoid stirring up the cortex. The surgeon should not press down on the capsule when the cortex is milky because this will stir cortical lens material into the OVD. Using capsulorrhexis forceps after the initial capsule puncture instead of a bent needle puts less pressure on the capsule. The more the capsule is depressed, the more cortex that will be expressed. If the OVD becomes mixed with cortex and the view degrades, an irrigation- aspiration probe can be inserted and the contaminated viscoelastic material removed. More OVD can be injected to improve visibility and the tear can continue under high magnification. If the surgeon anticipates visibility problems at the outset, he or she should stain the capsule before it is punctured.
- A final problem for beginning surgeons has to do with ergonomics. Many surgeons like to hold the capsulorrhexis forceps with one hand. I prefer maneuvering them with 2 hands. I use my right hand to grasp the forceps; I keep my left index finger on the instrument just outside the incision. I find I have more control if I pivot the forceps inside the eye around my index finger. It is also important, as I mentioned earlier, to stay at the center of the phacoemulsification incision and not up against the edge or roof of the tunnel. The beginning surgeon is usually so interested in what is happening at the tip of the forceps that no attention is paid to what is happening to the eye as a whole. Often the eye is badly rotated, full of corneal striae, and virtually out of the field of the microscope. Staying wound neutral throughout the procedure is important for maximizing visibility.
V. SPECIAL CONSIDERATION IN INFANTS AND CHILDREN
Infants and children have soft lenses and elastic capsules. They also have little scleral rigidity. When an incision is made into the pediatric eye, the anterior chamber shallows, putting additional stress on the anterior capsule. When the capsule of an infant or child is punctured, it often radializes immediately.
- It is important to fill completely, or even overfill, the anterior chamber of an infant’s eye with OVD before the capsule is punctured. Highly retentive cohesive viscoelastics are particularly useful for flattening the dome of the anterior lens capsule. It is best to have little or no convexity in the anterior capsule of an infant. The capsulorrhexis tends to run off the surface of the dome very quickly and it can radialize before the surgeon has a chance to gain control.
- It is important to make the initial capsulotomy small and central and to spiral it out to a very small diameter. I generally shoot for an initial size of 3 to 3.5 mm in infants. It never stays this small; it always goes wider. If the initial tear is extended to 4 or 4.5 mm, it will be very difficult to maintain that diameter as the capsulorrhexis proceeds.
- Whenever it is evident that the capsulorrhexis is going wide, the surgeon should stop and inject more viscoelastic to flatten the dome of the lens again. It may be necessary to do this several times before the capsulorrhexis is completed. There is no problem making a capsulotomy 3 mm in diameter, removing the cataract, and going back to enlarge the capsulotomy secondarily. Much greater control will be achieved once the bulk of the lens is removed from the capsule.
- The general problem of capsule elasticity, posterior pressure, and tendency for radialization may continue into teenage and early adult years. Increasing scleral rigidity and lens rigidity and decreasing capsule elasticity combine to make the capsulorrhexis easier with time and increasing age.
VI. CAPSULORRHEXIS RESCUE
The capsulorrhexis does not always proceed the way the surgeon wants. Sometimes intralenticular pressure makes it run wide. This is particularly common in the white intumescent cataract, which produces the Argentinian flag sign. Intralenticular pressure is also common in the infant eye. Less commonly, posterior pressure from a tight lid speculum, a Valsalva maneuver, a sudden uncontrolled pull on the flap, or an inadequate OVD fill of the anterior chamber can cause the capsulorrhexis to run wide.
When the surgeon sees that the capsulorrhexis is beginning to run wide, he or she should immediately stop and assess the situation. Are any of the causative factors listed above at play? If yes, they should be addressed. It never hurts to inject additional amounts of highly cohesive OVD to flatten the dome of the anterior capsule. If the tear has not gone too far out, flapping it over and pulling tangentially in a shearing fashion should allow the surgeon to regain control.
If this does not work, a technique espoused by Brian Little should be tried next. His technique is to inject OVD to completely fill the anterior chamber, unfold and flatten the capsular flap, grasp the flap near the root of the tear, and put traction on the flap in the capsular plane—backward first, then centrally, but never anteriorly.As the tear circles back around, the usual technique can be resumed.
*Dikutip dari Buku Essentials of Cataract Surgery 2nd Ed, halaman 92-95