6   Anterior and Posterior Capsulorhexis

The development of continuous-tear curvilinear capsulorhexis (CCC) by Gimbel and Neuhann in the 1990s was essential for the development of modern phacoemulsification techniques such as divide and conquer. The CCC technique has stood the test of time, and the tear-resistance and subsequent lens stability it provides has made it a standard in phacoemulsification surgery. The advantages of these qualities can also be utilized in planned extracapsular cataract extraction as well manual small-incision cataract surgery.^1–6

Creating a tear-resistant CCC provides the basis for complication–free phacoemulsification. An intact capsular bag is critical for safe and complete removal of the native lens, cortex stripping, and vacuum polishing the capsule as well as for implant centration and stability. Even in cases with zonular dehiscence, an intact capsular bag may enable placement of a capsular tension ring and an in-the-bag posterior chamber lens implant.

Although intra- and postoperative complications of CCC are not common, there is the potential for vision loss as a direct result of mismanagement of complications. Thus, should a problem occur during the creation of the CCC, the surgeon should immediately attempt to rectify it so as to prevent further compromise to the surgery and minimize the risk of postoperative complications. In our experience, properly performed CCC with in-the-bag intraocular lens (IOL) placement has reduced the incidence of intra- and postoperative complications.^7–21

Capsular Anatomy

It is helpful to consider the key anatomic features of the lens capsule and to keep them in mind while performing both CCC and phacoemulsification. The capsule is an elastic basement membrane made up of type IV collagen (Fig. 6.1). This basement membrane is laid down by the lens epithelial cells, which reside just inside the capsule; residual lens epithelial cells are responsible for the postoperative capsular opacification and capsular contraction. This may result in the need for neodymium:yttriumaluminum-garnet (Nd:YAG) laser treatment following cataract extraction.^22–25 The zonules insert on the anterior capsule over an area 2 to 2.5 mm in breadth. Therefore, if the crystalline lens is on average 10.5 mm, and the anterior zonules insert 2.5 mm from the equator, a capsulorhexis greater than 5.25 mm may tear some of the more anterior zonules. Occasionally, a zonular fiber may insert more anteriorly than usual. This can redirect the progressing circular capsule tear toward the equator. The capsule may be as thin as 2 to 4 µm at the posterior pole. It is thickest (17 to 23 µm) near the anterior and posterior equator where the zonular fibers attach.²⁶ The anterior capsule can be as thick as 14 µm in adults and continues to increase in thickness with age. The posterior capsule may be particularly fragile in cases with congenital posterior lenticonus and posterior polar cataract. Age-related or corticosteroid-related posterior subcapsular (PSC) cataracts involve migration and enlargement of the lens epithelial cells posteriorly where the capsule is thinnest.²⁷

The surgeon must also be aware of such patient factors as age, disease (e.g., pseudoexfoliation or Marfan’s syndrome), or a history of ocular trauma, which may predispose the patient to zonular weakness or dehiscence. Zonular dehiscence is discussed in Chapter 25.

Surgical Technique of Continuous Curvilinear Capsulorhexis

There are a variety of methods described for performing CCC.^1,28–31 One technique is to puncture the anterior capsule centrally with a sharp needle or instrument. This is then exchanged for a capsulorhexis forceps, and the CCC is completed as described below.

Gimbel and Kaye¹ described their currently preferred method of forceps-puncture CCC in 1997. This technique has the advantage of using only a single instrument but does require the use of an ophthalmic viscoelastic device (OVD).

This technique begins with OVD injection into the anterior chamber (AC) following a corneal paracentesis or after the creation of a scleral tunnel or clear corneal incision. An OVD filling of the AC before the CCC is performed is important, as it flattens the anterior capsule and provides both resistance to forward pressure of the vitreous against the lens and protection to the corneal endothelium. Forward pressure that is not neutralized leaves the anterior capsule convex, which creates a vector force that will tend to drive the tear peripherally. The OVD minimizes the anteriorly directed force of the lens against the tearing anterior capsule. Thus, the tendency for the capsular tear to extend toward the equator is minimized. Some eyes, such as pediatric eyes and short eyes, require a highly cohesive OVD to flatten the anterior capsule.

To create the initial central anterior capsular puncture, the capsule forceps should have sharp tips and be held with the tips together and with the tips pointing toward the center of the lens. Assuming a superior incision to describe the clock hour positions, the capsulotomy is started just proximal to the center by applying downward and forward pressure to puncture the capsule (Fig. 6.2a). After the initial puncture is made, the tip of the forceps is lifted and extended forward a bit to create either a short linear or triangular tear toward the 6 o’clock position. The left arm of the triangular or linear tear is then grasped and gently guided to the 3 o’clock position by pulling slightly and moving the tip of the forceps toward the left (Fig. 6.2b). Without releasing the forceps, if possible, the tear is continued around to approximately the 12 o’clock position, where it can be easily re-grasped closer to the point of tearing for better control. The continuous tear can then proceed counterclockwise with two or three more re-grasps near the point of tearing to complete the CCC using a shearing technique (Fig. 6.2c). The capsule should be re-grasped as often as necessary to direct the tear in the direction desired.

Fig. 6.1 The lens capsule is made up of type IV collagen. It is a basement membrane laid down by the lens epithelial cells residing just inside the capsule.

The CCC can also be achieved using a bent needle or cystotome.³² Under OVD cover the bent needle or cystotome is used to make an initial puncture at the planned center of the CCC. The opening is then extended to make a linear or triangular tear of the desired length. The flap is then turned over, and tearing forces are applied to the tearing edge to create a circular capsulorhexis. Similar to the forceps capsulorhexis, the CCC is completed by drawing the tear inward for the two torn ends to join with the ending tear joining the initial tear from the outside to avoid a triangular break in the circle.

Avoidance of Peripheral Extension of the Tear

To avoid the tendency for the tear to proceed peripherally, the tip of the forceps may have to be just behind the advancing tear. The tip of the forceps should then be directed such that the force of the movement is in anticipation of the intended direction of the tear. At times, the required vector force of the tear is such that the force needs to be directed centrally or even almost opposite to the advancing tear direction as the circular tear is created. If a tear begins to extend peripherally in spite of the above techniques, the surgeon should stop immediately. The possibility of positive posterior pressure should be entertained (Fig. 6.3a). This pressure will cause the lens to move anteriorly and create a vector force toward the periphery. This force will drive the tear relentlessly into the equator. Causes of increased posterior pressure should be minimized. The speculum may have to be loosened, the drapes relaxed, and if topical anesthesia is being utilized and the patient is squeezing the eyelids, additional sedation may be necessary. Once these problems are remedied, additional OVD, preferably a highly cohesive one, should be added to further deepen the AC and flatten the anterior capsule/lens surface (Fig. 6.3b). This will reduce the tendency for the capsular tear to extend peripherally, and the rhexus can be completed. Then the capsular edge should be gently grasped immediately adjacent to the tear, and guided back with a careful movement directed centrally or against the extending tear (Fig. 6.4a).

Fig. 6.2 (a) The Gimbel-modified Kraff-Utrata forceps is used to create the initial anterior capsular tear as well as to perform the continuous-tear capsulorhexis (b,c). (b) The edge of the capsule is regrasped and guided in ate a controlled fashion to complete the capsulorhexis at the 3 o’clock position ear by drawing the tear inward (c).

Fig. 6.3 (a) Positive pressure from behind the lens creates a vector force that directs the tear to extend toward the equator. (b) Deepening the anterior chamber with dispersive viscoelastic flattens the anterior lens surface and counteracts these vector forces. The tear can then be redirected toward the center of the nucleus. Step 1: Fold the flap over the anterior capsule. Step 2: Re-grasp the flap near the tear. Step 3: Pull the flap in the opposite direction and toward the center to redirect it. Step 4: Once redirected, continue the capsulorhexis. (c) The tear cannot be redirected. It is therefore completed from the opposite direction.

Sometimes it is helpful to fold the tearing part of the capsule over on itself and then grasp it near the tear and tear it firmly toward the anatomic center of the lens as described by Little et al³³ (Fig. 6.4b–d). If an anterior tear cannot be turned back toward the center using the forceps, a small area of the can-opener technique can be utilized to remove this section of the capsule. A small strip of capsule encompassing a short tear can be created to avoid radial extension of the tear.^2,22 If the tear cannot be turned back, and it extends well into the equator, the capsulorhexis can be completed from the opposite direction (Fig. 6.3c). This type of rhexis is obviously not continuous. Therefore, in this situation, or anytime a capsule tear disappears under the iris such that its peripheral extent cannot be visualized, the surgeon must expend due care to prevent the extension of the tear around the equator and into the posterior capsule. In this circumstance, hydrodissection may have to be omitted, excess pressure during phacoemulsification avoided, and cortex removal performed carefully to avoid extension of the radialized tear. Additional principles of management in these cases are discussed below.

Capsulorhexis Technique for Patients with Small Pupils

In patients with small pupils, the use of a centrally directed tearing motion may move the side of the lens into view and enhance the visibility of a capsulorhexis edge that is larger than the pupil opening. In this setting, extreme care must be taken to ensure that, at the completion of the rhexis, the ends of the tear overlap, that is, the tear is completed from the outside toward the inside of the capsule edge. This will ensure that there are no nicks or triangular edges in the capsule. During later steps in the procedure, the angled edge has the potential to extend peripherally. It may be helpful, in addition, to use a second instrument through the paracentesis to gently push the iris aside for better visibility. The use of additional OVD between the iris and anterior capsule is another method to lift and help enlarge the pupillary aperature.³⁴ Although some surgeons may be able to accurately assess the location of the tear by noting the location of the folding of the anterior capsule as the CCC proceeds, even if it is hidden by the iris, direct visualization of the CCC as it is being performed is recommended.

If the pupil is too small for these measures, it should be enlarged with one of the methods described in Chapters 4 and 5. Devices such as iris retractors or other pupil expansion devices such as the Malyugin ring can also be used to stretch the pupil to achieve an optimal-sized CCC.^35,36 If the resulting CCC is too small, it can be enlarged by using Gills-Welsh/Vannas scissors or microscissors directed in a tangential counterclockwise direction to begin a slightly more peripheral tear (Fig. 6.5a). Care should be taken not to close the scissors completely, as the tips closing will create a jagged end to the snip. The new flap edge created in this way can then be directed using a forceps (Figs. 6.5b–e).

Fig. 6.4 Little Rescue Technique (a) Step 1: Fold the flap over the anterior capsule. (b) Step 2: Regrasp the flap near the tear. (c) Step 3: Pull the flap in the opposite direction and toward the center to redirect it. (d) Step 4: Once redirected, continue the capsulorhexis.

The capsule opening must provide adequate access to the cataract. In cases of nuclear mature, hard brown cataracts, too small a rhexis predisposes to rupture of the posterior capsule during the hydrodissection (see Chapter 7). Nuclear manipulation is facilitated by the creation of a large enough CCC. The likelihood of creating a tear in the anterior capsule during phacoemulsification is minimized as well as providing for more maneuvering. Should a tear occur, however, the risk of more significant complications exists. The tear does not have to extend very far to progress to or through to the equator, which would destabilize the remaining anterior capsular support for a sulcusplaced IOL.

In the case of white, cortically mature cataracts, an initially small CCC to be enlarged later in the procedure may be considered. This is discussed in greater detail below.

Intraocular Lens Optic Size

We recommend that the final CCC should be only about a millimeter smaller and concentric with the IOL so that no portion of the anterior capsule CCC edge can fuse to the posterior capsule. The IOL edge is held more posteriorly by the intact CCC and therefore creates a mechanical barrier to lens epithelial cell migration behind the IOL. This theory is confirmed by the decreased incidence of Nd:YAG capsulotomy seen in association with the thick angular edge of acrylic IOLs. In addition, a CCC that is concentric with the optic edge balances the forces of the contracting capsular bag, hence minimizing the tendency for tilting postoperative IOL movement. In a randomized controlled study, Hollick et al³⁷ reported a significantly higher incidence of posterior capsule wrinkling and opacification with a larger capsulorhexis that lay completely off the optic surface.

An asymmetrical CCC will result in part of the CCC being over the IOL and part being larger than the IOL and therefore against the posterior capsule. This may lead to subsequent asymmetrical fibrosis, which can nudge the lens to an eccentric position. In addition, where the anterior and posterior capsule is in contact, there will be fusion of the capsule. This often results in folds or a fibrous thickening and opacification of the posterior capsule.

A second reason that we favor a CCC smaller than, and concentric with, the optic is to maintain the compartmentalization of the eye even after Nd:YAG laser posterior capsulotomy. In a study that we conducted, we found that the initial pressure spike after Nd:YAG laser capsulotomy did not occur when the lens was completely sequestered in the capsular bag.⁸ There was a significant pressure spike when the lens was in the sulcus or when the IOL optic was partly in the bag and partly out of the bag. We postulate that the sequestering of the AC by the seal created when the optic of the IOL is completely covered by the capsulorhexis becomes a barrier against liquefied vitreous elements coming into the AC. This barrier may reduce the possibility of pseudophakic glaucoma.

Fig. 6.5 (a) A small continuous-tear curvilinear capsulorhexis (CCC) can be enlarged using Gills-Walsh Vannas scissors to begin a slightly more peripheral tear. (b,c) A forceps can then be used with the same technique as described for the primary CCC to gently guide the direction of the tear to create a larger CCC. (d,e) The new CCC is then carefully finished in an inward direction. This method may be used intentionally in a two-staged capsulorhexis technique in cases of mature cataract or in cases with a small traumatic opening in the anterior capsule.

A third reason to advocate a CCC smaller than the optic is that in the event of a posterior capsule tear, the technique of sulcus placement of the loops and optic capture through the CCC, as proposed by Neuhann³⁸ can be utilized. If the capsulorhexis is larger than the IOL optic, this technique cannot be utilized. Additionally, the more remaining capsule existing for sulcus IOL support, the easier sulcus placement becomes.

The ideal CCC size therefore, would allow a ¼- to ½-mm overlap of the capsule over the IOL edge. For a 5.5-mm optic IOL, this would be a rhexis of 4.5 to 5.0 mm, and for a 6-mm IOL the size would be 5.0 to 5.5 mm.

Anatomic Abnormalities of the Zonule

Postoperatively, in cases of pseudoexfoliation, weak zonules, and excessive inflammation, the anterior capsular edge may fibrose and contract, creating the capsular contraction syndrome. This may necessitate the use of the Nd:YAG laser to incise the thickened capsular rim.³⁹

In addition, Davison⁴⁰ has described the capsular block syndrome. It can occur intraoperatively or in the early or late postoperative period. Depending on the time of the capsular block, different materials accumulating behind the lens have been described.^41,42 It occurs in the presence of a small capsulorhexis and with implantation of silicone or acrylic IOLs. The material accumulates enough volume and pressure to eventually push the posterior capsule posteriorly and the IOL anteriorly, resulting in induced myopia. The syndrome is treated by Nd:YAG capsulotomy of the posterior capsule. The resultant equalization of pressure permits the posterior capsule and IOL to return to their normal pseudophakic configuration.⁴⁰

Continuous Tear Capsulorhexis with the Intumescent Cataract

Mature cataracts pose a challenge for performing a complication-free capsulorhexis due to the difficulties encountered in visualizing the edge of the tear. Visualization can be limited due to a poor or no red reflex and may be further compromised by liquefied cortex, which may flow into the AC as soon as the initial puncture is made.

Methods of improving visualization if capsule staining material is not available include slowing the microscope focus to obtain precise control, dimming the operating room lights, and using high magnification and non-coaxial lighting. A small-gauge cannula may be helpful in removing the opaque liquefied cortex to further enhance visualization during CCC. A method of turning off the microscope and room lights and then using a light pipe to provide side light to illuminate the tearing capsular edge has been described by Gills²¹ and Masket.²⁴

Trypan blue ophthalmic solution (VisionBlue®, D.O.R.C. International, Zuidland, The Netherlands) is most commonly used to stain and visualize the anterior capsule. It is available in 1-cc dose vials of 0.1% solution in phosphate-buffered sodium chloride. Trypan blue provides better visualization of the anterior capsule during both capsulorhexis and phacoemulsification.^43–45

Not infrequently in white, mature cataract cases a small capsulotomy may be more safely achieved than a large one. The nucleus with liquefied cortex may be under pressure. The initial entry into the capsule may be followed by the egress through the capsular opening of the liquefied cortical material. This may occur with sufficient pressure to extend the small penetration to a radial tear. Therefore, before penetrating the capsule the AC must be adequately filled with a retentive OVD. Once liquefied cortex has been removed, the intracapsular volume is decreased and the capsular edge can be visualized and the CCC can be enlarged. This is performed as described above after filling the capsular bag and AC with OVD and using a capsule scissors to create a tangential cut. This can then be enlarged to the desired size with capsulorhexis forceps (Fig. 6.5). Enlargement of the capsulotomy may be necessary for cortex removal and lens implantation. This two-stage CCC technique can also be used in cases with a small traumatic opening in the anterior capsule and for corneal endothelial protection in endocapsular cataract extraction.^9,22

A more thorough discussion of the intumescent cataract is found in Chapter 14 in the discussion of the mature cataract.

Intraoperative Capsular Complications

Anterior Capsular Tears

Anterior capsular tears can be avoided by using the techniques described above. In some cases, such as a small pupil or a mature cataract as noted earlier, a planned two-staged capsulorhexis may be indicated. This technique provides control and visualization during CCC and enables enlargement of the capsulorhexis as needed either before or after lens implantation. By purposefully creating an initially small capsular opening, tears resulting from loss of control during CCC may be reduced. However, tears or the creation of a zonular dehiscence during phacoemulsification becomes a greater risk by contacting the CCC edge with the phaco tip, or by puncturing, tearing, or pulling on the anterior capsule with a second instrument.

Anterior capsule tears may also occur during cortex removal. This is of particular concern when removing the subincisional cortex. With a one-handed technique using the standard rigid irrigation and aspiration (I/A) tip in an effort to reach the cortex, the aspiration port must often be placed out of view under the iris. Often, the tip is rotated such that the aspiration port is facing superiorly or posteriorly. These maneuvers, while necessary to engage the cortex, cause distortion to the incision, creating poor visibility and increasing the risk of inadvertently engaging the capsular edge and creating a tear. In an effort to prevent this problem, some surgeons advocate the use of a two-handed I/A technique, with one cannula in one hand for balanced salt solution (BSS) inflow and the other cannula in the other hand for aspiration. The cannulas are placed through two paracenteses openings. This improves visibility and control for aspiration of the subincisional cortex. Alternatively, the angled, soft silicone I/A probe is well suited to removal of subincisional cortical material. The maneuverability combined with the softer tip in this type of I/A handpiece provides better visibility and protection against anterior and posterior capsule tears. Finally, it should be noted that subincisional cortex, when present, is more easily removed if a cortical cleaving hydrodissection has been performed.

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