Capsulorrhexis - Cataract Surgery, 3rd Edition

Cataract Surgery, 3rd Edition

PART IV – Phacoemulsification

Chapter 14 – Capsulorrhexis

Thomas F. Neuhann, MD,
Roger F. Steinert, MD

Contents

	•	History
	•	Development of Capsulorrhexis
	•	Terminology
	•	Principles and Advantages of Capsulorrhexis
	•	Current Standard Techniques of Capsulorrhexis
	•	Difficult Situations
	•	Special Surgical Techniques
	•	Complications and Pitfalls

CHAPTER HIGHLIGHTS

	≫	Technical tips
	≫	Several techniques illustrated
	≫	Management of complicated capsulotomy

History

The rebirth of extracapsular cataract extraction in its modern, refined, microsurgical version has brought with it the need for an adequate technique for anterior capsulectomy. Vogt's technique, using toothed forceps to grasp and rip out a part of the anterior capsule, was definitely thought to be too traumatic to both the endothelium and the zonular apparatus, as well as too uncontrollable. Kelman's “Christmas tree” technique was a considerable improvement in terms of both better control and less trauma. Soon, however, interconnected perforations of the anterior capsule with a cystotome in a circular pattern, the “can-opener” technique, became the most popular and almost universally used approach worldwide. It allowed relatively precise control of the diameter and shape of the excised anterior capsular flap and, by using a cannula infusion cystotome, allowed the anterior chamber to be maintained throughout the procedure. Later, in an attempt to use the anterior capsule for additional endothelial protection during the surgical procedure, the “letterbox” technique was developed and gained considerable popularity, especially among surgeons preferring planned extracapsular cataract extraction. This two-stage technique also offered considerable advantages for controlled lens implantation into the capsular bag because the anterior capsular window was not completed until after implantation of the intraocular lens (IOL).

Although these techniques and their modifications adequately fulfilled the aim of removing the central part of the anterior capsule, they proved to have one major disadvantage. The necessary manipulations during either phacoemulsification or extraction of the entire nucleus were almost invariably associated with the creation of one or more tears of the remaining peripheral anterior capsular rim, extending at least into the capsular equator. This has a number of undesirable side effects. Not infrequently, the tears extended beyond the capsular equator and into the posterior capsule, accompanied by the associated complications of vitreous loss and loss of the nucleus into the vitreous, especially when occurring early in the course of the operation. In addition, these tears divided the peripheral anterior capsule into a number of separate flaps, which could then interfere with the surgical procedure, especially the aspiration of peripheral cortical remnants. Finally, accumulating clinical evidence led an increasing number of surgeons to prefer IOL implantation into the capsular bag over sulcus implantation; however, it became evident after a while that at least 50% of the IOLs thought to be securely implanted with both loops in the capsular bag had, in reality, only one fixation loop in the bag or none at all. Anterior capsule tears were frequently the source of IOL loops escaping from the capsular bag.

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Development of capsulorrhexis

From what may later be called a general surgical “instinct” (which was later fully substantiated by the clinical experience), a number of surgeons had realized for some time that the ideal anterior capsulectomy would be one with a smooth, continuous, ideally circular, margin, but the technique to achieve this ideal remained elusive. In 1984, Howard Gimbel in Calgary, Alberta, Canada, and Thomas Neuhann in Munich independently, but simultaneously, developed a technique that essentially consisted of tearing rather than cutting out a central anterior capsular window. What was so decisively new about this technique was not the tearing itself in fact, it had been used for part of the anterior capsulotomy before. The difference was that the tear was brought around the entire circumference, resulting in a circular opening with no beginning or end, nor an outward-pointing edge from which a radial tear could originate. Gimbel and Neuhann used different technical approaches, yet with the same underlying basic principle, benefiting from the specific tearing properties of the lens capsule. Much like cellophane, the lens capsule splits easily from a sharp-edged point of departure, whereas it is extremely resistant to tears into a smooth margin. Both surgeons showed their first video film in 1985 – Gimbel at the annual meeting of the American Society of Cataract and Refractive Surgery in Boston and Neuhann at the meeting of the German Ophthalmological Society in Heidelberg. In his film, Neuhann also proposed the term capsulorrhexis. The first formal publication in a scientific journal appeared in 1987;^[1] in 1990 Gimbel and Neuhann published a joint article in the Journal of Cataract and Refractive Surgery.^[2]

Both Gimbel and Neuhann have always regarded capsulorrhexis as having been developed by them equally, though independently, respectfully acknowledging the work of others on which the technique is based.^[3]

Terminology

The term kapsulorhexis was proposed by Neuhann to make it clear that it was a truly new surgical technique, a new surgical principle (namely tearing instead of cutting) and not just another modification of previous techniques. Gimbel originally called his technique “continuous tear capsulotomy.” Bringing both their terms together yielded “continuous curvilinear (more general than circular) capsulorrhexis” (CCC).

Principles and advantages of capsulorrhexis

Capsulorrhexis leaves a capsular bag with mechanical and structural integrity, despite there being an opening large enough to deliver the lens through. This is due to the lens capsule's shearing property, which resembles cellophane. Although the capsule tears easily when departing from a sharply pointed defect in an edge, requiring a minimal amount of force, much greater force is required to rupture a straight, smooth margin.^[4–6] This property is commonly experienced when opening the cellophane wrapper of a package. Tearing open a cellophane-wrapped package is greatly facilitated when the manufacturer provides a linear break in the wrapper and an arrow to that point with the instructions “Start here.” If an opening in the lens capsule has a continuous smooth margin, the remaining capsule stays on stretch like a trampoline, as if no hole were present. The obvious advantages of this are as follows:

	1.	No tags or flaps of anterior capsule remnants interfere with surgery, especially the aspiration of the peripheral cortex.
	2.	The mechanical forces exerted onto the capsule, and thereby onto the zonules, are minimized.
	3.	The capsular bag is deeply open during surgery with a closed-system approach: the posterior capsule is ballooned posteriorly and thus held on stretch, reducing the danger of it getting caught and broken, while the anterior capsule remains on stretch horizontally, maintaining intracapsular space for surgical maneuvers.
	4.	With an intact capsulorrhexis, manipulations within the capsular bag (which are always in some way associated with distention), such as tilting or cracking the nucleus or implanting an IOL, no longer entail the risk of extending radial tears in the anterior capsule into the posterior capsule.
	5.	Capsulorrhexis is the prerequisite for a reproducibly secure, verifiable, and permanent capsular bag fixation of IOL implant haptics.^[7]
	6.	Even in the case of a posterior capsule defect, regardless of its size, an intact anterior capsulorrhexis provides the possibility of implanting an IOL safely into the ciliary sulcus. If the capsulorrhexis opening is well centered and smaller than the optic, it may be used additionally to fixate the implant by capturing the optic (“rhexis fixation”) posteriorly while the haptics remain anterior in the ciliary sulcus.
	7.	It can be learned “by doing” without exposing the patient or the physician to any risk.
	8.	Capsulorrhexis is the prerequisite for all attempts to minimize or control posterior capsule opacification after cataract formation by the principle of a sharp posterior edge of the IOL.

Current standard techniques of capsulorrhexis

There are three basic choices that a surgeon must make for establishing his or her standard technique:

	1.	The instrument: a cystotome or a forceps
	2.	The access: via the main incision or via a side-port paracentesis
	3.	The medium: irrigation with fluid or viscoelastic.

Although all three options may theoretically be freely combined, in practice there are two main options:

	1.	A bent needle or cystotome through a side-port paracentesis under fluid irrigation (or viscoelastic)
	2.	A forceps through the main incision (or a side-port paracentesis) under viscoelastic.

For the needle technique, a 23-gauge needle is bent to about a one-quarter circle and with the tip 45° away from the bevel. The needle is mounted on an infusion handpiece, connected to the gravity-fed infusion at maximum height. With the infusion continuously running, the anterior chamber is entered through the side port, the size of which should just be large enough to permit passage of the needle. The chamber will thus be formed as deep as possible. The anterior capsule is perforated near the center with the needle tip and then slitted in a curvilinear manner with the cutting side edge of the needle in such a way that the desired radius of the capsulorrhexis is reached in a blend-in manner (Figure 14-1). When about to reach the desired circumference, the capsule is lifted from underneath, close to the leading tear edge, and pushed upward and forward to propagate the tear. Soon, enough of a flap will be created to permit flipping it over and engaging it from its backside, its epithelial side, now facing up toward the cornea. The needle engages the flap by exerting just enough pressure to create the friction necessary for engagement, but not enough pressure for the needle tip to perforate. Having the capsular flap thus engaged, it is torn in a circular fashion (Figure 14-2A) by appropriately influencing the tear vectors. The more distant the point of engagement is from the leading edge of the tear, the more centripetally one must tear; the closer the point of engagement is to the leading edge, the more directly the tear will follow the direction of traction. It is, therefore, most advisable to refixate the tear with the cystotome point frequently, close to the leading edge – a basic principle that governs the entire technique and its variations. When brought around full circle, the tear is blended into itself, automatically coming from outside in, which is a basic prerequisite to avoid a discontinuity.



Figure 14-1 In the standard technique for capsulorrhexis, a central puncture with a cystotome followed by an arched curve creates a slit. The capsular flap is pulled and lifted at its edge.



Figure 14-2 A, Flap is inverted, and the underside of the capsule edge, now anterior, is engaged with the needle tip or forceps and pulled circularly. B, Circular tear capsulorrhexis is illustrated using a capsulorrhexis forceps. C, Perfect large circular capsulorrhexis is seen on red reflex through the operating microscope.

The same technique can also be performed with the anterior chamber filled with a viscoelastic substance. In this instance one would basically follow the same guidelines, with the exception of the continuously running infusion.

TECHNICAL TIPS

Starting the tear somewhere in the center in the capsule has the advantage of virtually eliminating the possibility of creating a discontinuity that would be caused by finishing the tear from inside out; this becomes especially valuable in cases with reduced visibility (e.g., small pupils, no red reflex). The tear must be performed over the full 360° in the direction in which it was started.

Puncturing the capsule within the contour of the capsulorrhexis has the disadvantage that it may cause a stellate burst (with extensions to the capsular periphery) if the needle is not perfectly sharp. If such a burst goes unnoticed (e.g., for visibility reasons) or if its extensions reach too far peripherally to be recovered, a peripheral tear will result at this location (Figure 14-3). In addition, with this technique the risk of inadvertently completing the capsulorrhexis from inside out is slightly higher. On the other hand, by beginning with a puncture, the surgeon has two options as to where to proceed with the tear, developing it and bringing both ends together at the point of maximal control (Figures 14-2C and 14-4). Today, most surgeons probably start somewhere in the capsular center.



Figure 14-3 Use of a blunt needle to puncture the capsule in the periphery may create a stellate burst with outward pointing edges from which peripheral tears may originate.



Figure 14-4 After a stellate opening, a continuous curve capsulorrhexis can be achieved by tearing in both directions from the most peripheral edges of the stellate opening.

The forceps technique makes the use of a viscoelastic substance mandatory to maintain the anterior chamber. When using a Utrata-type forceps, access through the main incision, which for that purpose must be fully widened to at least 3mm, must be chosen. When using a coaxial forceps of a pars plana-type construction, such as the Koch forceps, a paracentesis opening of appropriate size is sufficient. Otherwise, the forceps technique follows the same principles and guidelines as outlined earlier for the needle technique (see Figure 14-2B).

TECHNICAL TIPS

With irrigation, the capsular flap floats freely in the anterior chamber, improving visualization, maneuverability, and control. Conversely, the incision must be tight, necessitating a very accurate and meticulous fulcrum technique. A viscoelastic substance is more forgiving with a leaking incision. However, visualization, especially of the leading tear edge, may be impaired as the torn-out portion of the capsule gets larger, crimps, and is “frozen” in the viscoelastic, possibly mixed with anterior cortex, and may lead to loss of control over the flap. Therefore, the flap should always be well spread out over the undersurface.

TECHNICAL TIPS

A drawback of the forceps technique is that it necessitates a larger incision and, therefore, can be safely performed only with a viscoelastic agent. Conversely, grasping with a forceps is somewhat more secure than grasping with a needle and is independent of the solidity of the underlying cortical material (which, with the needle technique, really constitutes the “second hand”). This latter aspect also makes it the technique of choice in some special situations (see later).

Two additional aspects regarding capsulorrhexis techniques merit discussion: firstly, the question of the ideal size of the anterior capsule opening. Ideally, the size should be:

	•	as large as possible. The larger the opening, the easier the manipulation of the nucleus
	•	small enough to allow the anterior capsular margin to just cover the optical part of the IOL, completely sealing it into the capsular bag. This “sealing-in” effect appears to be a prerequisite for the inhibitory effect of sharp IOL edges on the formation of secondary cataract.

Secondly, the limitations in obtaining the ideal size, which include the following:

	•	The size of the pupil
	•	The central insertion of the zonular fibers.

The surgeon must recognize that corneal magnification will make the initial capsulorrhexis appear larger than its true size; once the IOL is inserted, the capsulorrhexis will appear to have shrunken in comparison with the IOL optic.^[8]

An asymmetric opening, that is, partly covering and partly not covering the optic margin, is to be avoided because of its potential for causing IOL optic decentration.

Learning capsulorrhexis

One of the major advantages of capsulorrhexis is that it can be learned “by doing,” without exposing the patient to any additional risk. Coming from whatever prior technique of anterior capsulotomy, the surgeon may begin along the given guidelines. If the tear starts moving into an unwanted direction, the surgeon can revert to the previous technique.

TECHNICAL TIPS

When using Utrata-type forceps through the main incision, insidious loss of viscoelastic is very likely to occur. This leads to a flattening of the anterior chamber and, consequently, a forward movement of the lens. This, in turn, leads to an increase of the outward vector forces inherent in the lens capsule, making it increasingly more difficult to keep the tear from running outward. Knowing the danger means banning it: refilling the chamber with viscoelastic patiently as losses occur can prevent this most frequent source of losing control over the capsular tear. Instruments that open only at the tip (coaxial vitrectomy type) introduced through a paracentesis reduce viscoelastic loss. Use of a low-molecular-weight, retentive viscoelastic agent also reduces the amount of viscoelastic lost through the main incision.

To practice, good surrogates for the lens capsule are cellophane, as used in shrink-wrap packages, or tomato skin. Pigs' eyes, with thicker and more elastic anterior capsules, can serve as excellent models for learning to master the difficulties in infantile and juvenile capsules.

Difficult situations

Capsulorrhexis is best learned under ideal conditions: good-to-adequate pupillary dilation, good red reflex, deep anterior chamber, and no positive pressure.

The following four basic types of difficulties present challenges for capsulorrhexis:

	1.	No red reflex
	2.	Small pupil
	3.	Positive back pressure
	4.	Extreme elasticity: the infantile/juvenile capsule.

Although they often occur in various combinations, each of these situations is discussed separately to clarify the basic principles of management.

No red reflex

When there is no adequate reflex from the fundus to retroilluminate the surgical site for visualization, other clues must be used to “detect” the capsular margin in order to control the tear at every moment. The introduction of capsular dyeing, usually with trypan blue, is certainly the most notable progress in solving problems of visualization of the anterior capsule (for details, see Chapter 27, The Intumescent Cataract). Additional help can be contributed by other technical details; for instance, inclining the eye slightly with regard to the observation and illumination paths can sometimes produce enough of a red reflex to safely proceed. Also, side illumination, in addition to, or instead of, coaxial illumination, can be helpful. Often, one can benefit from the orange-skin-like specular reflex of the coaxial light source on the capsule. Constant manipulation of the eye position in such a way that the progressing tear edge remains in that reflex zone outlines the tear very clearly. Also, one should always choose as high a magnification as possible that does not interfere with the necessary overview. Finally, proceeding slowly in small steps and with frequent regrasping will help the surgeon not to lose control of the flap.

The small pupil

In addition to precluding visualization of the capsular area where one wishes to place the tear, the small pupil, in most instances, also causes reduction of the red reflex. Therefore, all of the previous measures are advisable as needed. (For an extensive discussion of small-pupil techniques, see Chapter 21.) When the pupil is smaller than the desired capsulorrhexis diameter, one may combine different principles. With experience, the surgeon will be able to tear a capsular flap “blindly,” larger than the pupil diameter. Starting from the capsular center within the visible pupillary area will ensure completion from “outside in.” If one chooses to start the capsulorrhexis from the peripheral circumference, the needle may be used to retract the pupillary margin to the desired eccentricity, sliding along it while creating the initial slit and developing the flap away from the site of entry. Previous dyeing of the capsule with trypan blue can be helpful in judging the flap diameter. Measures to increase the pupillary diameter may include injection of atropine and/or epinephrine into the anterior chamber; filling the chamber with viscoelastic; peeling off the fibrous lining of the posterior aspect of the pupil, which so often limits its dilation; dilation of the pupil with self-retaining hooks or dilators (e.g. Malyugin ring) or only local dilation of the pupil with a second instrument through a second paracentesis, sliding along the pupillary edge with the progression of the tear. Multiple snip-sphincterotomies or sphincter stretching has been advocated. When in doubt, I prefer a keyhole iridotomy, which is later resutured, because it restores the iris diaphragm and thereby helps prevent later broad adhesions between an atonic, flaccid iris and the anterior capsule, or even the posterior capsule from migrating behind the implant. Finally, another possibility is performing phacoemulsification through an initially smaller capsulorrhexis and enlarging it later in a two-step technique.

Positive pressure

Positive pressure tends to force the tear outward. Therefore, these cases require an intentionally small diameter to begin with – which can be widened as soon as the pressure is relieved – and continuous, pronounced centripetal traction in small steps, regrasping frequently close to the tear edge. Also, exerting counterpressure by pushing the lens back with viscoelastic is very helpful.

Infantile/juvenile capsule

The special challenge in infantile and juvenile capsulotomy is the increased elasticity of the lens capsule. When placing tension on an anterior capsule flap, it will first distend considerably before propagating the tear; once the tear starts, it has a great propensity to get lost outward because of the tractional “preload” and the elasticity, creating a pronounced outward pulling vector force. It is, therefore, advisable to aim for a tear that is smaller than one really wishes it to be because it will become wider by itself. The capsulorrhexis tear should progress slowly, in small steps, and with frequent regrasping and directing the tearing more centripetally than for a typical adult cataract. The disadvantage of the extreme elasticity, however, has a positive side also. Should a discontinuity in the capsulorrhexis margin occur, it is, for the same reason, less likely to progress peripherally when due caution during surgery is maintained.

The only situation in which capsulorrhexis is impossible in principle is the totally fibrosed capsule. Cases of heavy fibrosis or fibrous plaques extending so far peripherally that one cannot tear around them without hitting zonules mandate the use of scissors to cut through the fibrosis. The scissor cut should end just barely at the margin of the fibrosis, and from there on into regular capsule the opening should be continued as a tear.

TECHNICAL TIPS

The intumescent lens combines the difficulties of positive pressure with those of a lack of red reflex. Filling the anterior chamber with a thick viscoelastic is advisable to block opaque liquefied cortex from leaking into the aqueous humor and compromising visibility. Usually a forceps technique is preferable because the cortex is liquefied and, therefore, presents no resistance to a needle tip. The second major problem is the increased pressure within the capsule as a result of the swollen lens, which increases the risk of uncontrollable extension of the partially completed capsular opening to the periphery. The surgeon must try to counteract this tendency by filling the anterior chamber with a high-viscosity viscoelastic, to the extent of indenting the anterior lens pole. Sometimes one can decompress the lens by making a small puncture in the central anterior lens and aspirating some of the liquid content through the puncturing needle.

Special surgical techniques

Applying the same basic principles as described earlier has led to the development of maneuvers that may prove helpful in certain situations.

Bimanual forceps

In certain situations, it may become difficult to grasp and manipulate the capsular flap using just the needle tip. The surgeon may, in these situations, prefer to change to a forceps technique. However, when removing the irrigating cystotome, the lens diaphragm may come forward, causing the tear to divert outward. To avoid this, a bifurcated spatula of the Bechert type (or similar modification) is introduced into the chamber through an opposite paracentesis. The capsular flap is pinched between the needle tip and spatula tip. The capsule flap can then be manipulated as with a forceps.

An alternative is to introduce viscoelastic through the second paracentesis before withdrawing an irrigating cystotome needle. The anterior chamber will remain formed while the surgeon changes to a forceps.

Bimanual/bi-instrumental capsulorrhexis

When the zonules are very weak, pulling centripetally on the flap may risk disinsertion of the capsule. Holding the flap with capsular forceps with one hand and gently pushing the peripheral margin outward (centrifugally) with a blunt instrument can propagate the tear with less stress on the zonules. The surgeon should strongly consider placing a capsule tension ring as soon as the capsulorrhexis is completed in these very tenuous cases.

Posterior capsulorrhexis

Leaving the posterior capsule intact is one of the major objectives of extracapsular surgery. Nevertheless, this goal cannot always be attained. Examples are a dense, nonremovable posterior capsular opacification that will doubtlessly interfere significantly with vision; an infantile cataract in which rapid opacification of the osterior capsule is inevitable and neodymium:yttrium-aluminum-garnet (Nd:YAG) laser capsulotomy is impractical (see Chapter 26, Surgical Management of Pediatric Cataracts and Aphakia); or, most frequently, accidental posterior capsular rupture. In all of these cases, the opening in the posterior capsule should have the same quality, if possible, as that of the anterior capsulorrhexis, namely being not further extendable because of a continuous smooth margin. This can be obtained by applying the same technique of capsulorrhexis as that of the posterior capsule. In cases of intentional posterior capsule opening, the posterior capsule should be nicked centrally with a needle tip, viscoelastic is injected through the first tiny triangular defect to separate and posteriorly displace the anterior vitreous face, and the posterior capsular triangle is grasped by capsular forceps and torn out as a curvilinear posterior capsulorrhexis.

When an unintended capsular defect occurs, extension can be limited by the same technique, as long as the original posterior capsule rent is limited enough to permit this. This technique will then preserve a capsular bag into which an IOL can be implanted securely, maintaining all the advantages of intracapsular implantation.

“Rhexis-fixation”

In the case of a posterior capsular rupture that cannot be limited by posterior capsulorrhexis, another maneuver may maintain most of the advantages of capsular implant fixation. If the anterior capsulorrhexis margin is intact and smaller than the IOL optic, the IOL can be implanted into the ciliary sulcus and the optic captured, that is, “buttoned in” backward through the capsulorrhexis in the technique first described by Tobias Neuhann. This provides secure mechanical fixation of the lens by the capsule and centration in relation to the capsular opening, with the lens haptics only acting as secondary support. The IOL in this position will have the same optical power as though intracapsularly implanted.

Complications and pitfalls

The following are three classic intraoperative complications that can occur with capsulorrhexis:

	1.	Discontinuity of the anterior capsular margin
	2.	Tear into the zonules
	3.	Diameter being too small.

The following are two classic postoperative complications:

	1.	Purse-string contraction
	2.	Incarceration of viscoelastic.

Discontinuity of the anterior capsular margin

The major causative factors in this instance are: completing the capsulorrhexis “from inside outward” (Figure 14-5), nicking an originally intact margin with the second instrument during lens extraction, or breaking the rim with the activated phaco tip. A discontinuity in an otherwise intact CCC margin will, in most cases, extend into a radial tear into the capsular fornix; it will do so very readily because the distensive forces will concentrate on this single point of weakness (Figure 14-6). The risk of this radial tear extending around the capsular fornix into the posterior capsule increases with sparse and friable zonules and with all maneuvers that distend the anterior capsular opening, such as hydrodissection, expression of the nucleus, nuclear fracturing techniques that rely on pushing the nuclear sections widely apart, and IOL implantation maneuvers.



Figure 14-5 Illustration of a capsulorrhexis that is progressively enlarging so that it finishes from the inside toward the outside.



Figure 14-6 Discontinuity in the capsule is created by an inside-to-outside finish. From that point, a peripheral tear may originate. The same situation results when a previously intact capsulorrhexis margin is cut with an instrument or with the phacoemulsification tip.

TECHNICAL TIPS

The most important rule is to always close the circle from outside inward. This will automatically occur when starting the tear somewhere in the center of the capsule, as described earlier (Figure 14-7). If the flap breaks off during the course of the tear, the surgeon must be sure to grasp the remaining flap and continue the outward pointing tear edge. When a discontinuity happens, timely recognition is of key importance. Its edge must instantly be grasped with forceps and blunted off by blending into the main contour (Figure 14-8). When a tear has occurred into the capsular fornix, utmost caution is warranted not to extend the tear further by avoiding the previous risk factors. A relaxing counterincision opposite the first tear may be considered. A radial tear does not preclude capsular bag implantation if manipulations are appropriately gentle. The lens haptics should be placed at 90° from the radial tear. Such a tear is a relative contraindication for implantation of plate haptic IOLs.



Figure 14-7 When an inside-outside discontinuity occurs, it can be repaired by picking up the resulting triangle, inverting it, and tearing centripetally to bring the tear edge back toward the capsulorrhexis margin, ultimately blending it in.



Figure 14-8 A, Starting the capsulorrhexis from the center makes it virtually impossible to end in an inside-out fashion. Creating a continuous margin is much more likely. B, When a capsulorrhexis is completed correctly, a small centrally pointing tag is created. When the capsulorrhexis is incorrectly finished, a discontinuity occurs.

Tear into the zonules

If the tear encounters zonular fibers, either because it is too peripheral or because zonules are inserted abnormally centrally, it cannot readily be continued. Further tearing will risk deviation of the tear to the periphery, like tearing paper alongside a ruler (Figure 14-9). With the help of high microscope magnification, an optimized red reflex or specular reflex, and optimal focusing, the responsible zonules can be identified and their insertions removed from the capsule with the needle or forceps tip. Then the surgeon brings the tear more centrally and continues. Sometimes this situation can also be managed by grasping the flap close to its edge and briskly pulling it centrally. This maneuver, however, carries a higher risk and is only advised when the more controlled approach does not seem possible.



Figure 14-9 When a capsular tear encounters a zonular fiber, the resulting zonular forces direct the tear peripherally toward the equator.

Healon 5 (Pharmacia), with its exceptionally high density, can also help redirect an extending capsulorrhexis tear. A relatively small amount of Healon 5 is injected into the angle, with the expanding bolus reaching the edge of the tear. The dense Healon 5 will help redirect the tear back centrally.

Capsulorrhexis with too small a diameter

If the surgeon realizes that the diameter of the CCC is becoming smaller than desired, he or she may just continue the tear in a spiral manner until the desired diameter is reached (Figure 14-10).



Figure 14-10 In performing the capsulorrhexis, the surgeon may realize that the original arc is too small. The capsulorrhexis can be expanded by “spiraling” outward to the desired diameter and then “closing the circle.”

When a large and hard nucleus coincides with a very small diameter of the anterior capsular opening, hydrodissection may lead to a pressure-induced rupture of the posterior capsule. The nucleus blocks the capsular opening, and the injected fluid has only one way to escape: posteriorly. An initial bulging forward of the lens followed by a sudden, snaplike drop backward indicates the occurrence. In such an event, conversion to planned extracapsular cataract extraction is indicated. A lens loop behind the nucleus is necessary. Consideration should be given to “posterior assisted levitation” with either an instrument or injection of viscoelastic through a pars plana sclerotomy to support the nucleus from behind.^[9]

Purse-string contraction

The remaining lens epithelial cells on the back surface of the anterior capsule postoperatively undergo fibrous metaplasia. The contraction of this fibrous layer is normally counteracted by the centrifugal forces of the zonular apparatus. However, when either the zonules are weak (e.g., in pseudoexfoliation, trauma, and retinitis pigmentosa) or the fibrosis is excessive (e.g., after increased postoperative inflammation, with some silicone lenses and other factors) or in combinations of both, the anterior capsular opening may contract (“capsular phimosis”) (Figure 14-11). The contracture may block the visual axis or exert excessive contracture on the ciliary body, leading to hypotony.^[10]

TECHNICAL TIPS

In cases identified at risk for excessive contraction, the surgeon should aim for a relatively large opening, implant lenses with stiff haptics with an overall diameter of about 13mm, consider implantation of a capsular tension ring (or even two), and perhaps avoid silicone as a lens material. Postoperatively, these cases should be monitored closely. At the first sign of contraction, the anterior capsular margin should be incised with an Nd:YAG laser at three or four equidistant locations. Extension of these discontinuities need not be feared at this stage, owing to the fibrous lining itself and the already secure sealing in of the IOL.



Figure 14-11 Postoperative photograph illustrating contracture of the capsulorrhexis. This situation is more common when the original capsulorrhexis is 4 mm or smaller.

Incarceration of viscoelastic (“capsular block syndrome”)

Residual viscoelastic may be trapped behind an implant when the IOL optic margin is completely covered by the capsulorrhexis. The retained viscoelastic attracts water osmotically and swells. The implant acts as a valve, permitting the influx of aqueous behind the lens, but not the efflux of the thick viscoelastic–aqueous mixture. This phenomenon is more pronounced with plate haptic lenses but may happen with all types of implants. The consequence may be gross inflation of the capsular bag with posterior ballooning of the posterior capsule and anterior displacement of the IOL, heralded by a shallow anterior chamber and a myopic shift in the refraction.^[11]

This complication can best be avoided by complete removal of the viscoelastic material, actively aspirating it from behind the lens. Once capsular block has occurred, the retained material can be released into the anterior chamber by puncturing the anterior capsule beyond the optical margin with Nd:YAG laser pulses. If the pupil cannot be dilated adequately to expose the anterior capsule peripheral to the IOL optic, a laser peripheral iridectomy can be made, followed by further laser pulses deeper through the iridectomy to open the anterior capsule. If this cannot be achieved, the posterior capsule must be punctured, releasing the material into the vitreous. Prophylactic treatment with topical steroids, nonsteroidal anti-inflammatory agents, and glaucoma medications is given because of expected transient inflammation and elevated intraocular pressure from the abruptly released viscoelastic agent.

References

[1]. Neuhann T.: Theorie und operationstechnik der kapsulorhexis. Klin Monatsbl Augenheilkd 1987; 190:542-545.

[2]. Gimbel H.V., Neuhann T.: Development, advantages, and methods of the continuous curvilinear capsulorrhexis. J Cataract Refract Surg 1991; 17:110-111.

[3]. Assia E.I., Apple D.J., Barden A., et al: An experimental study comparing various anterior capsulectomy techniques. Arch Ophthalmol 1991; 109:642-647.

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Contents

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Cataract Surgery, 3rd Edition

PART IV – Phacoemulsification Chapter 14 – Capsulorrhexis

PART IV – Phacoemulsification

Chapter 14 – Capsulorrhexis