19

Capsulorhexis

Tobias Neuhann

History

“Cataract surgery has been developed to its ultimate state and any improvements from this date will be insignificant,” said one of the most renowned US ophthalmologists in 1962. Fortunately, this statement proved to be wrong throughout the four decades to follow until today and ophthalmological progress has continued to solve major problems and challenges managing both a multitude of different anatomic conditions as well as of material characteristics and designs of ophthalmic implants and devices.

One of the major problems of the late 1970s and early 1980s was pupil capture of intraocular lenses due to sulcus implantation. This problem was seriously by the members of today’s ASCRS. As result of this discussion was favorising the idea of intraocular lens implantation into the capsular bag. The Simcoe loops (modified C-loop), a new design of that time, provided a considerable improvement in intracapsular centration compared to the generally used J-loops. However, the problem of decentration remained in 10–15 percent.

Analyzing this decentration showed that disregarding targeted and correct endocapsular implantation tears of the anterior capsule originated, so that at least one loop luxated into the sulcus, thus mostly forming the precondition for later decentration. The Kelman Christmas-tree and also the Galand letter-box technique as well as the most frequently applied can-opener technique produced jagged edges which formed a locus minoris resistentiae, so that the logical conclusion was to develop a method to open the capsular bag in such a way that only smooth edges were created.

Based on mutual experiences and observations my brother, Thomas E Neuhann, and myself were the first to describe the reproducible method of capsulorhexis.1

At the same time and completely independent of our development Howard Gimbel worked on the same idea, produced the same result and called his new technique continuous tear capsulotomy. In the attempt to find the most suitable and precise term for the new technique and to take the original terminological approach of both inventors into account Neuhann and Gimbel finally decided to call their mutual development “continuous curvilinear capsulorhexis” 2 the CCC. It has become the standard technique for planned anterior as well as posterior capsular opening. Taking into account that two independent developments had been made in the “Old” as well as in the “New World” and that this approach has remained the method of choice for opening all kinds of capsules until today shows that the CCC simply was the most logical conclusion summing up the experiences of the past (Fig. 19.1).3,4

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Needle Technique

Using the needle technique, first an initial puncture of the anterior capsule within the central area to be removed is required. This puncture is then extended in a curve-shaped manner to the targeted eccentric

FIGURE 19.1 CCC with IOL in situ; clinical picture

FIGURE 19.2 Basic principle of the

CCC

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Another option is to place the first puncture directly within the planned curvature and start the rhexis with a curved enlargement of this tiny hole. In this case the tear is brought around on both sides, until the ends finally join together as already described above.5

The needle technique can be performed using BSS or viscoelastics. In addition the below factors are essential for the success of the needle capsulorhexis:

Needle

1.Although many different needles could theoretically be applied, only the 23 gauge needle is recommended. The lumen of this type of needle is just sufficient to produce a pressure exchange between the anterior chamber and the BSS irrigating bottle.

2.The metal of such a cannula offers just enough rigidity to provide the necessary resistance for difficult manipulations. Needles with higher gauge do not meet the described requirements, and this alone may cause a CCC failure—even though this fact is unfortunately not generally known.

3.A higher, i.e. positive pressure in the anterior chamber compared to the intracapsular pressure

FIGURE 19.5 Stellate burst created by a blunt needle

is mandatory. This becomes especially noticeable with intumescent lenses, where the lens protein is hydrated resulting in a volume increase inside the capsular bag, which results in a considerable increase in the endocapsular pressure as a consequence. The necessary prerequisite for a successful capsulorhexis is a pressure of the anterior chamber that is greater than or equal to that inside the capsular bag. The pressure in the anterior chamber can be adjusted via the height of the infusion bottle.

4.The needle tip should be as sharp as possible, since a blunt needle will lead to stellate burst, which is more difficult to handle (Fig. 19.5).

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Comparison of the Needle and Forceps Technique

The forceps technique is easier to learn. For this reason it is also the most frequently applied capsulorhexis technique. However, applying the forceps technique, the use of viscoelastics is mandatory.

The advantage of the needle technique is that it is economical, since it can be performed with application of BSS as well as viscoelastics and the cost of the needles is neglectable.

To point out the difference between the needle and the forceps technique, the following example might be appropriate: To turn over a page of a book you can take the sheet between two fingers and turn it from one side to the other (this is what you do with the forceps), or you take a moistened finger, press the page a bit down and then turn it over (that is what you do with the needle; the counter hold is the cortex). With this in mind the consequences appear quite clear cut. I will always use a needle technique, the initial puncture peripheral or central, for the great majority of my cases. The forceps I will use in those situations where the needle—so to say—lacks the other branch. This is mainly the case in the presence of a liquefied cortex or in cases where a secondary enlargement of the capsulorhexis diameter is required.5

The Two-Step Needle Technique

Today the two-step needle technique belongs to the past. Here, the capsule is first opened peripherally with the needle below the incision and the incision is enlarged in a curveshaped manner to the right and left applying the sharp edges of the needle accordingly, so that a larger flap is created. By bending the same needle now in such a way that the flap, which was transformed into an incision, is flipped around the tear is completed in the known way.5

Capsulostripsis

This technique was invented by F.Rentsch and described by J.H.Greite at the 1995 ASCRS meeting (Fig. 19.7). This approach is specifically designed for difficult cases, where the intracapsular pressure exceeds that of the anterior chamber. With this method a vitrector with infusion sleeve is used to create an irregular opening in the anterior capsule. Experience shows that a guillotine-type cutter is preferable to a rotating system. To prevent the capsule from tearing, extremely slow motion is essential. The resulting opening in the capsule is a jagged, however, the rounded, mouse-bite-like cuts of the vitrector tip nevertheless produce a stable rim, because of the favorable distribution of forces of this series of mini arcs.

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FIGURE 19.7 Capsulostripsis opening and IOL in situ (Courtesy of JH Greite)

This technique is rather time-consuming compared to conventional CCC performed by an experienced surgeon. On the other hand, it is easy to perform and provides a reliable alternative for hypermature or even milky cataracts without sufficient red reflex and other cases with difficult CCC, such as subluxated lenses or cataracts in children with elastic capsules.6–8

Diathermy Capsulotomy

Another alternative method to create a circular and stable aperture of the anterior capsule that has been quite frequently discussed for some time is diathermy capsulotomy. In the attempt to create a circular rim in opening the capsule with this method mostly bridges remain that have to be cut with micro-scissors. To perform this technique, the use of viscoelastics is required. The method is especially recommended for intumescent cataracts, but a number of surgeons find it easier to perform than the CCC in general.

However, even though the postoperative result may resemble that of a capsulorhexis, it should not be neglected that comparative studies demonstrated that the CCC is more stable and has a perfectly smooth edge, in contrast to the diathermy opening, which is marked by multiple irregularities and offers less stability and less elasticity. Hence, the application of diathermy in routine cataract surgery cannot be recommended.9–11

Capsulorhexis Size

The author prefers a capsulorhexis that is somewhat smaller than the optic diameter of the IOL to be implanted. The CCC provides enough stability and elasticity to allow intraocular manipulations even with a smaller anterior aperture without any hazard. In fact, no study has ever been able to show that a larger CCC diameter relative to the IOL optic is more advantageous. Supporting this preference, comparative studies found that in

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addition a slightly smaller capsulorhexis diameter seems to reduce the postoperative opacification of the posterior capsule.12–14 When it comes to rhexisfixated IOL implantation, this type of IOL is completely excluded in the presence of an excessive rhexis diameter, for instance in case of damage of the posterior capsule, which is another reason why the rhexis size should be kept somewhat smaller than the lens optic. Furthermore, study results suggest that a smaller capsulorhexis size is likely to produce a smaller postoperative IOP as well as better effectivity of sharp edges of some IOL designs.

Difficult Cases

Small Pupil

The fact that several different methods are available to intraoperative extend a narrow pupil has made capsulorhexis easier to perform in such cases. The generally applied measures in such cases are:

•Removal of the pupillary membrane;

•Bimanual stretching;

•Removal of synechiae;

•Iris hooks;

•Pupil dilator.

To perform a capsulorhexis in the usual way, first the pupil is extended using one of these methods. This is followed by creation of the CCC with needle or forceps.

Pseudoexfoliation Syndrome, Uveitis und Pigmentosa

With these patients often a thickened anterior capsule can be clinically observed, which is hard to tear. Another common finding in such cases is also a subluxated lens, which is only diagnosed intraoperative. An important aspect of surgery in such patients is to strictly refrain from a rather small capsulorhexis, as the result of this might be an undesired shrinkage of the anterior capsule.

Capsules of Infants, Children and Juveniles

Due to the high elasticity of the anterior capsule a smaller rhexis must be performed in such patients than is the case with adults. Here it must be taken into account that the rhexis opening still enlarges by 0.5 to 1.0 mm after completion of the rhexis. Regarding pediatric posterior capsulorhexis, the necessity of an accompanying anterior vitrectomy is controversially discussed. Here, in a number of cases a self-sealing closure provided by the IOL could be successfully achieved.15

A new method to create a CCC in infantile and juvenile capsules was recently described by Nischal.16 This new modification is called the two-incision push-pull capsulorhexis. Here, two stab incisions are made proximally and distally to the incision approximately 4.5 to 5.0 mm apart in the anterior capsule, thus outlining the diameter of

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the planned capsulorhexis. One end of the distal edge of the proximal anterior capsule stab is grasped using a fine capsulorhexis forceps and gently pushed toward the corresponding point of the distal stab incision and continued until halfway to the distal stab incision. A corresponding procedure is performed with the proximal edge of the distal anterior capsule stab incision until half a CCC has been created. An analogous procedure is performed on the other side, resulting is a complete capsulorhexis opening.

This technique is specifically designed to meet the special conditions of the elastic pediatric capsule, because the tearing forces are always directed to the pupillary center, thus resulting in a curvilinear tear. The technique can be applied for the anterior as well as posterior CCC.

Capsulorhexis in Calcified Capsules or Anterior Flaps

These cases mostly require a completely individual CCC, where an additional application of Ong 01 Vannas scissors or comparable tools is required.

Posterior Capsulorhexis

A series of indications, such as large-scale capsular fibroses, damage of the posterior capsule17 or less frequent conditions like persisting arteria hyaloidea as shown by Greite at the 1990 ESCRS meeting may require a primary or secondary posterior capsulotomy. In the same way as the anterior CCC also the posterior capsulorhexis offers the preservation of a stable capsule. First the anterior capsulorhexis is performed using forceps or needle in the usual way and phacoemulsification or IOL explantation are carried out as preferred. The anterior segment is filled with viscoelastics to stabilize the posterior capsule. Then the posterior capsule is first only perforated and viscoelastics are injected prior to further manipulations. This instillation of viscoelastics behind the capsule is vital to prevent a vitreous prolaps. The posterior CCC can then be carried out with needle or forceps in the same way as an anterior CCC. In some cases a successive vitrectomy may be necessary to prevent the vitreous from invading the capsular bag via the posterior opening. The remaining tire-like capsular residue provides a stable and secure site for intraocular lens fixation.18 Gimbel especially recommends a posterior capsulorhexis in pediatric cataract surgery to avoid secondary membrane formation after cataract extraction.19

Capsulorhexis in the Presence of a Broken Posterior Capsule

If ruptures of the posterior capsule occur intraoperative and cannot be transformed into a posterior CCC placement of the IOL in the ciliary sulcus with the known disadvantages of this fixation as listed below seems to be the only option. To avoid this, rhexis fixation of the IOL is the possible solution. The author at the 1991 ASCRS Film Festival first presented the applicable technique. The precondition for this method is an intact anterior capsulorhexis with a diameter that is smaller than that of the IOL optic. In rhexis fixation, the lens optic is manipulated behind the anterior capsulorhexis rim with a spatula, while the loops remain in the sulcus. This approach leaves the IOL optic securely positioned inside the capsule in a button-like manner (Figs 19.8 and 19.9). This method is also an

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option for pediatric surgery, where mostly a posterior capsulorhexis is performed as well to prevent secondary cataract formation.25,26 The only restriction using this method is the implied exclusion of plate-haptic IOLs.

The advantages of this technique are:

•No sunset or sunrise syndrome are possible;

•Rotation and decentration are excluded;

•The calculated lens power is effective because of the reliable location of the optic;

•Iris chafing cannot occur;

•Vitreous prolaps is prevented by stable endocapsular placement of the implant;

FIGURE 19.8 Principle of rhexis fixation of an IOL

FIGURE 19.9 Rhexis fixation of an

IOL; clinical picture

• Secondary cataract formation is avoided due to removal of the posterior capsule.

Howard Gimbel described a variation of this technique in the middle of the 1990s. In his modified approach, he used the opened posterior capsule as support/fixation location in

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infantile or juvenile lens implantation, thus trying to prevent a vitreous prolaps calling this procedure capsular capture.19

Anterior and Posterior Capsulorhexis

M.J.Tassignon works on that same topic to fixated IOLs on the capsulorhexis. Her technique is called “bag in the lens”. The IOL has no haptics but only a hinge of the IOL edge and is fixated while clipping the two capsular leaves in this edge hinge. Further clinical investigation is currently running to evaluate this very interesting IOL design and technique.

Insufficient Red Reflex

In cases of an insufficient or completely missing red reflex due to mature or hypermature cataract blue staining of the anterior capsule is now possible to increase the visibility for

performance of the CCC. This method became very fast the recommended technique in such cases.20–24

Another option to deal with this problem is capsulostripsis instead of a capsulorhexis, as already described earlier in this chapter.

Complications and Pitfalls

There are three major potential intraoperative problems an ophthalmic surgeon may find himself confronted with performing the CCC:

Discontinuity of the Capsulorhexis

To avoid this complication the capsulorhexis should never be completed from inside out. But also stellate bursts originating from initial puncturing attempts with a blunt needle may destroy an intact capsular margin in the course of surgery to form a discontinuity which presents a most critical source for a radial tear down into the peripheral capsule. In the presence of such a discontinuity the entity of mechanical forces inside the capsular bag concentrate on this weakest point, and the only effective remedy is to repair the discontinuity immediately. If such a repair by transformation of the tear into a smooth edge is no longer possible, utmost care must be employed in the remaining intracapsular manipulations.

Tear into the Zonula

If a tear has already reached a zonular fiber, a conventional repair of the capsulorhexis is too hazardous, because it might result in further rupture right along the zonular fiber toward the equator. To cope with this critical situation two different approaches are available. One way is to follow the end of the respective zonula down to its origin, gently free it with the forceps and use this singled-out zonular fiber to tear a smooth-edged

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curve to unite with the otherwise intact capsulorhexis. The other and more risky approach is to firmly and briskly pulls the flap toward the center.

Insufficient Capsulorhexis Size

Realizing during the process of circular tearing that the capsulorhexis will be smaller than originally planned is not really an intraoperative problem. In such cases all the surgeon has to do is to direct the vector forces in such a way that the circle is not closed but rather proceeds further into the periphery. With this kind of spiral-shaped enlargement the CCC diameter can be increased to the desired size. Once the capsulorhexis is large enough the circle is closed in the usual way.

Captured Viscoelastics

If the anterior capsular rim adheres to the anterior IOL surface after implantation viscoelastics residues may be trapped behind the lens. Usually this problem does not occur if the viscoelastics are carefully removed. If it does, mostly the lens blocks the passage for the viscoelastics into the anterior chamber and at the same time allows the aqueous to invade the area behind the implant, thus pushing the IOL against the cornea. In such a situation an additional puncture of the peripheral anterior or—in comparably narrow pupils—posterior capsule is required to provide for a release of the viscoelastics into the anterior chamber or the vitreous, respectively.

Disadvantages of the CCC

As of the introduction of the CCC, a new problem was described over time, which is the capsular shrinkage syndrome or capsular phimosis.27 This complication is not known in any other capsulotomy technique and solely relates to the CCC. The genuine pathomechanism could not be clarified until today. Clinically this problem can be observed especially in patients suffering from Pseudoexfoliation syndrome (PEX), uveitis, retinopathy pigmentosa or subluxation in combination with PMMA or silicone IOL implantation. All these diseases have a considerably reduced number of zonula fibers in common. The fact that up to now this complication has not been described in patients suffering from these diseases in context with an acrylic IOL implantation allows the conclusion that a certain mechanical interaction of acrylic lens surface and capsule successfully prevents this problem, so that the acrylic IOL is presently the lens of choice in such cases. This, however, is not valid for low-water acrylics.

A potential remedy to avoid the problem of capsular shrinkage is the insertion of a capsular tension ring.

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Discussion

The development of the capsulorhexis definitely introduced a new age in small incision cataract surgery. This applies both for the development of new phacoemulsification techniques as well as for the important role phacoemulsification plays in modern cataract surgery in general. In addition, the CCC has opened the gate for the development of a multitude of new and refined foldable IOLs and implantation devices, because it was the first capsulotomy technique to offer a stable and reliable anterior capsular opening, so that today even a toric correction is possible with implantation of posterior chamber IOL.

While capsulorhexis as a principle is well established, its technical performance is being refined and advanced. In this context I would like to stress once again that capsulorhexis in essence really is not a technical procedural detail but a fundamental surgical principle. Its theory needs to be well understood—then its technical details emanate as a logical consequence. In other words, you should be convinced that this anterior capsular opening is what you want to have.

Also secondary surgery including intraocular lens exchange benefits from the specific properties of the capsulorhexis aperture. Intraocular manipulations in the anterior as well as posterior segment of the eye belonging to the realm of phantasy only two decades ago are feasible today; now that circular apertures at any required number and dimensions in both the anterior and the posterior capsule can be created securely and without taking the risk of tear originating from intraoperative manipulations. And what is more, the structural integrity of the capsule is not only maintained throughout the course of surgery but also postoperatively, thus forming the precondition for stable, safe and permanent IOL placement. From its invention 20 years ago the CCC has managed to form a reliable basis for all new developments of the ophthalmic market and no comparable technique to open the capsular bag has been invented ever since. In this way, the CCC occupies its place as one of the important milestones of ophthalmology.

References

1.Neuhann T: Theorie und Operationstechnik der Kapsulorhexis. Klin Monatsbl Augenheilkd 190:542–45, 1987.

2.Gimbel HV, Neuhann T: Continuous curvilinear capsulorhexis (letter). J Cataract Refract Surg 17:110–11, 1991.

3.Assia EI, Apple DJ, Barden A et al: An experimental study comparing various anterior capsulectomy techniques. Arch Ophthalmol 109(5):642–47, 1991.

4.Krag S, Thim K, Corydon L et al: Biomechanical aspects of the anterior capsulotomy. J Cataract Refract Surg 20(4): 410–16, 1994.

5.Neuhann T: Capsulorhexis, Phacoemulsification, Laser Cataract Surgery and Foldable IOLs, In Agarwal S, Agarwal A, Sachdev MS, et al: (Eds): Jaypee Brothers Medical Publishers (P) Ltd: New Delhi 81–88, 1998.

6.Wilson ME, Bluestein EC, Wang XH et al: Comparison of mechanized anterior capsulectomy and manual continuous capsulorhexis in pediatric eyes. J Cataract Refract Surg 20(6):602– 06,1994.