CAPSULORRHEXIS COMPLICATIONS

The development of continuous-tear curvilinear capsulorrhexis (CCC) by Gimbel and Neuhann in the 1990s was essential for the development of modern phacoemulsification techniques. This technique has virtually replaced the can-opener capsulotomy as a safer, more tear-resistant method for opening the anterior capsule, even for planned extracapsular cataract extraction.1–5

Creating a tear-resistant CCC provides the basis for complication-free phacoemulsification. An intact capsular bag is critical for complete removal of the native lens and cortex and important for implant centration and stability. Even in cases with zonular dehiscence, an intact capsular bag may allow placement of a capsular tension ring and an in-the-bag posterior lens implant.

Although intraand postoperative complications of CCC are not common, there is the potential for vision loss as a direct result of mismanagement of potential complications. Thus, should a problem occur during the creation of the CCC, the surgeon should immediately attempt to rectify the problem so as to prevent further compromise to the surgery and minimize the risk of postoperative problems. In our experience, properly performed CCC with in-the- bag intraocular lens (IOL) placement has reduced the incidence of intraoperative and postoperative complications.6–22

CAPSULAR ANATOMY

It is helpful to consider the key anatomic features of the lens capsule and to keep these in mind while per-

forming both CCC and phacoemulsification. The capsule is an elastic basement membrane made up of type IV collagen (Fig. 5–1). 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:yttrium-aluminum-garnet (Nd:YAG) laser treatment following cataract extrac- tion.23–26 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 capsulorrhexis greater than 5.25 mm will tear some of the more anterior zonules. Occasionally, a zonule may insert more anteriorally than usual. This can redirect the tearing capsule toward the equator. The capsule may be as thin as 2 to 4 m at the posterior pole. It is thickest (17 to 23 m) near the anterior and posterior equator where the zonular fibers attach.27 The anterior capsule can be as thick as 14 m 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.28

The surgeon must also be aware of factors such as age, disease (such as pseudoexfoliation or Marfan’s syndrome), or a history of ocular trauma, which may predispose to zonular weakness or dehiscence. Zonular dehiscence will also be discussed in Chapter 9.

SURGICAL TECHNIQUE OF

CONTINUOUS TEAR CURVILINEAR

CAPSULORRHEXIS

There are a variety of methods described for performing CCC.1,29–32 One technique is to puncture the anterior capsule with a sharp needle. This is then exchanged for a capsulorrhexis 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 viscoelastic.

This technique begins with viscoelastic injection into the anterior chamber following the creation of a scleral tunnel or clear corneal incision, and paracentesis. Viscoelastic is important as it flattens the anterior capsule and provides both protection to the corneal endothelium and resistance to forward pressure of the vitreous against the lens. This forward pressure creates a vector force, which will drive the tear peripherally. Viscoelastic 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 neutralized.

To create the initial central anterior capsular puncture, the forceps should be held with the tips together in a tilted fashion pointing toward the center of the lens. Assuming a superior incision, the capsulotomy is started just proximal to the center by applying downward and forward pressure to puncture the capsule (Fig. 5–2A). After the initial puncture is made, the tip of the forceps is lifted and extended forward a bit to create either a triangular or linear tear toward 6 o’clock. The initial tear is then gently guided to the 3 o’clock position by pulling slightly and moving the tip of the forceps toward the left

(Fig. 5–2B). Without releasing the forceps the tear is continued around to approximately the 12 o’clock position, where it can be easily regrasped closer to the point of tearing for better control. The continuous tear can then proceed counterclockwise to complete the CCC using a shearing technique. Upon reaching the outer edge of the 9 o’clock tear the CCC is finished by drawing the tear inward (Fig. 5–2C).

AVOIDANCE OF PERIPHERAL

EXTENSION OF THE TEAR

To avoid the tendency for the tear to proceed peripherally, the tip of the forceps should always 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. Often, the vector force of the tear is such that the force tends to be directed somewhat centrally as the circular tear is created. If a tear begins to extend peripherally, the surgeon should stop immediately. The possibility of positive posterior pressure should be entertained (Fig. 5–3A). This pressure will cause the lens to move anteriorally 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 should 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 viscoelastic, preferably dispersive (i.e., Viscoat) should be added to further deepen the anterior chamber and flatten the anterior capsule/lens surface (Fig. 5–3B). This will alleviate the tendency for the capsular tear to extend peripherally. Then the capsular edge should be