Background

Continuous curvilinear capsulorrhexis (CCC) is the most reliable way of creating a secure and resilient opening in the lens capsule and was originally developed for use in phacoemulsification surgery where it has now been universally adopted1,2. It has more recently gained widespread popularity in the developing world for use in manual small incision cataract surgery (MSICS)3. The ‘three Cs’ also conveniently represent the three principal technical challenges, which require the rhexis to be Circular, Central, and the Correct size.

Capsulorrhexis comprises the most challenging step of phaco for most surgeons but its successful execution confers such huge functional advantages that safe endocapsular phaco has only become possible because of it.

When you have understood the basic principles and learned the correct techniques then you will have a solid foundation on which you can continue to build and develop your surgical skills in order to achieve a predictable and reproducibly accurate capsulorrhexis. Through continuing refinement you will, over time, master this important step of phacoemulsification.

Instruments

The choice of instruments for performing capsulorrhexis comprises either a bent needle referred to as a ‘cystotome’ (as was originally described) or, alternatively, capsulorrhexis forceps. A more recent addition to the choice of instruments is the femtosecond laser, at significantly greater cost compared with a bent needle.

A custom-shaped or preformed cystotome remains very popular today with many surgeons. Most use a 25 G needle. The advantages of using a needle (apart from cost) come from its small size: it can be used through a side port and causes minimal wound gape or chamber collapse. Its only disadvantage is the requirement to press downwards onto the capsule in order to gain any traction. This reduces the degrees of freedom for directional control of the tear.

Capsulorrhexis forceps, on the other hand, allow you to apply traction in any chosen direction but are relatively bulky (particularly the early parallel-action Utratta designs) and are more likely to cause wound gape and chamber collapse than a needle. However the newer designs are greatly refined and include hinged ‘cross-action’ and coaxial designs that cause minimal wound gape and give exquisite control of the tear through incisions down to sub-2 mm (Fig. 12.1). The high outlay cost, difficulty in cleaning, and susceptibility to damage of capsulorrhexis forceps all ensure that the bent needle is here to stay.

Fig. 12.1 Capsulorrhexis forceps.

The role of lasers in surgery is assuming an ever-increasing importance and, at the time of writing, the femtosecond laser has recently been used successfully on human eyes to create high precision incisions and accurate capsulorrhexis (Fig. 12.2).

Fig. 12.2 Femto laser caspulorrhexis, Zoltan Nagy.

Courtesy LenSx Lasers, Inc [Aliso Viejo, CA].

In practice your choice of instrument is one of personal preference. However, it behoves all surgeons to develop the capacity for adaptability which is, after all, the basis for evolution and survival. To completely master the art of capsulorrhexis a surgeon needs to be able to use both a needle and forceps with equal facility as neither of them alone is adequate for all situations. In addition, if you can use either hand and perform the tear clockwise and anti-clockwise then no capsulorrhexis is ever going to defeat you.

Capsulorrhexis technique

Like every step in phaco the devil is in the detail and this is particularly true when performing capsulorrhexis. Careful attention is needed to the finer points of the technique because small errors at this stage can result in significant complications later on through a domino or cascade effect.

As a beginner you should start with easy eyes: the ideal scenario is a shallow orbit, well-exposed globe, good akinesia and anesthesia, clear cornea, deep chamber, well-dilated pupil, and good red reflex. If you can tick all these boxes then you are off to a great start.

Avoid being in too much of a rush to get on with the surgery. You need to ensure that the patient is comfortable and well-positioned to facilitate good coaxial illumination. Most surgeons are pleasantly surprised by how dramatically a little methylcellulose on the cornea improves visibility and it needs only an occasional top-up during surgery.

The incisions are next. I would encourage you routinely to make two side ports, one either side of the main incision, separated by about 120°. This allows you universal access from either side with a cystotome, which is very helpful, and is necessary in any case if you use bimanual I/A.

If you favor a superior approach then ensure that the speculum is rotated such that the upper blade is positioned to either straddle the tunnel (if it is an open wire style) or be on one side or the other. This avoids snagging the forceps or needle on the speculum once your instrument is inside the eye. The stage is now set.

First and foremost beyond all else you must completely fill the chamber with viscoelastic, and keep it filled throughout. Try to backfill with a continuous wave as this is less likely to trap small pockets of aqueous. A cohesive OVD is preferable during capsulorrhexis as its retention in the eye is better than with a dispersive. With challenging cases, such as a shallow chamber or small pupil, the greater cohesiveness of a larger molecular weight OVD, which includes the more pseudoplastic Healon 5, are quite outstanding in this respect and provide an extraordinarily stable chamber.

The purpose of using OVD routinely is to positively pressurize the anterior chamber and thereby counterbalance the forward movement of the lens resulting from vitreous pressure. The lens capsule is an elastic basement membrane that is suspended by the zonules attached around its equator. You can appreciate that any forward movement of the lens will place the anterior capsule under additional tension as the zonules are put on stretch. The OVD pushes back the lens, flattens the anterior capsule, and neutralizes the capsular tension, which is the force that tends to re-direct the rhexis radially outwards towards the equator causing a proverbial tear-out. So the first article of faith is to keep the chamber full and deep at all times. To start with, discipline yourself to stop every 90° and refill the chamber even if you don’t think you need to: you will be surprised at how much OVD has escaped undetected.

Now for the rhexis itself. The first step is to initiate the tear which can be done using a keratome, a cystotome needle, the closed points of capsulorhexis forceps or with them open using just one jaw to puncture the capsule. The aim is to perforate the capsule at some point near its center. The initial tear then needs to be radialized and converted into a flap by either pushing the instrument forwards to form a small triangular flap, or alternatively extending the tear radially and then lifting the instrument forwards from under the capsule towards the cornea. This forces the end of the tear to break around circumferentially and form a flap.

As soon as you’ve made this hinged flap and turned it over, grasp the free peripheral edge close to the apex of the tear and, keeping it as flat as possible, propagate the tear parallel to the pupil margin. Until you are more experienced you should make only small tears and frequently re-grasp the flap at the apex. A key concept in order to avoid excessive wound distortion is to ‘pivot’ the instrument using the wound as the fulcrum and try to ‘float’ the instrument within the wound aiming (in theory) to avoid contact with the wounds internal surfaces and edges.

The force vector that tears the capsule in the intended direction is the resolution of two components: a centrally directed vector and a circumferentially tangential element. Ideally no vertical element is used. Some surgeons appreciate this issue of vector resolution much more intuitively than others, but everyone is capable of learning it. It is almost impossible to teach from a book and is much easier to understand in practice (Fig. 12.3). Another fact to appreciate is that capsulorrhexis is guided entirely visually as there is no tangible force feedback during capsular tearing.

Fig. 12.3 Capsulorrhexis traction vectors.

If you’ve managed to control the tear and keep it parallel to and a fixed distance from the pupil margin then your rhexis should fulfil two of the three ‘Cs’ by being Central and Circular. It may not however fulfil the criterion of the third ‘C’ which is for Correct Size. This is the most difficult one to get consistently right and is an inexact science. Have you ever seen any surgeon actually measure a capsulorhexis or use a template? As a novice, and often well beyond, the surgeon is too preoccupied during the rhexis with avoiding disaster to worry about the size of the resultant hole (which, early on, is almost universally undersized from being over-cautious). Preoccupation with size is the preserve of the experienced surgeon with sufficient confidence and skill to control it. If you shoot for a diameter of 5 mm this will give you an edge overlap of 0.25 mm for a 5.5 mm optic and 0.5 mm for a 6 mm optic (Fig. 12.4). Around 4 mm is the lower acceptable limit for the rhexis diameter: below this the risk increases of complications such as capsule block and anterior capsule tear, which are discussed below. This concentric overlap combined with a square edged optic appears to provide a mechanical barrier to lens epithelial cell migration across the posterior capsule and thereby reduce the incidence of posterior capsule opacification.

Fig. 12.4 Zonule-free zone in relation to capsulorrhexis sizing.

So how can you reliably judge the 5 mm diameter that you need? Well you have to resist the obvious temptation to use the pupil as your reference because its diameter is so variable. However, the vertical diameter of the cornea is fairly fixed at around 10 mm so you can use this as your reference. Think of the cornea as the optic disc and the rhexis as the cup and create a mental image a 0.5 cup/disc ratio. This should help you to get within the right range but only surgical experience will refine and hone your judgement. Some forceps have markings on the top surface of the jaws to assist with sizing the rhexis, which can be helpful (see Fig. 12.1).

The subincisional part of the rhexis is the most awkward segment to keep under control because of wound distortion, mechanical discomfort, and instrumental obscuration of the tear. The easiest part of the rhexis is the first 90° from wherever you start. So why not start with the subincisional sector first and turn the most difficult part into the easiest part? This sounds disarmingly simple but it really does work (Fig. 12.5). However, in practice it is counter-intuitive and requires the self-discipline to withstand the temptation to tread the path of least resistance and begin the rhexis diametrically opposite the incision, or off to one side.

Fig. 12.5 Rhexis, start subincisionally.

It might be helpful finally to summarize the important principles for successful capsulorhexis with a few alliterative guidelines as an aide memoire:

Equipment

You need a 2.5 ml or 5 ml Luer-Lok syringe and a suitable cannula. What constitutes a suitable cannula is a matter of continuing debate. There are straight, curved, dog-legged, hockey-stick, right-angled, open-ended, side-ported, round-lumen, flat-lumen, 23 G–30 G all at your disposal. Many work well. The larger diameter (lower gauge) and shorter cannulae give higher flow rates. A curved profile gives easier access to either side at 3 and 9 o’clock. Flatter tipped cannulae generate a fan-shaped jet of fluid. Try different designs and find what works better for you. The author prefers a 23 G curved cannula with a flat tip.

Technique

Correct technique is critical for consistent success with hydrodissection. First, it helps to expel any residual OVD out of the chamber before attempting hydrodissection. The presence of OVD, particularly if cohesive, partially obstructs the free flow of fluid around the lens and back out of the bag. This can increase the chances of capsular block and posterior capsular rupture during hydrodissection.

Insert the tip of the cannula immediately beneath the edge of the rhexis in the subcapsular plane. Then slide it radially outwards towards the equator about 2–3 mm. Most surgeons are too tentative to begin with and do not go out far enough. In this case the fluid just refluxes around the cannula and back into the chamber, along the pathway of least resistance. The nearer the tip is to the capsular equator then the easier it is for the fluid wave to pass around the back of the lens. The cannula tip is blunt so it will not go through the capsule equator with normal use but will simply move the whole nucleus if it pushes up against the equatorial fornix.

Before injecting fluid you should lift the tip of the cannula slightly forwards in order to tent the anterior capsule away from the cortex, thereby opening up the cleavage plane of the subcapsular space. Do not bury the tip of the cannula into the cortex or you will perform a superficial hydrodelineation and have to strip out all of the cortex later on.

A brisk pulsed injection of fluid is usually needed to initiate the fluid wave. As you continue to steadily inject fluid the wave usually becomes visible, silhouetted by the red reflex, as it passes behind the nucleus (Fig. 12.7).

Fig. 12.7 Hydrodissection wave, cortical split.

During this first phase of hydrodissection the fluid accumulates behind the nucleus, filling the bag and pushing the nucleus forward, creating a ‘mini capsular block’. This is seen by the surgeon as an early ‘nuclear lift’ (Fig. 12.8) and is often accompanied by central splitting of the anterior cortex and epinucleus, or ‘cortical split’ (see Fig. 12.7).

Fig. 12.8 Early hydrodissection, mini capsular block with nuclear lift.

At this point the surgeon has to press down on the bulging nucleus in order for the trapped fluid to propagate forwards as a subcapsular fluid wave that breaks the anterior cortico-capsular adhesions in its wake (Fig. 12.9). The nucleus then drops back and fine radial striations appear in the anterior cortex, created by the fluid making slit-like channels in the cortex as it is forced forwards (Fig 12.10).

Fig. 12.9 Hydrodissection, ballotte nucleus.

Fig. 12.10 Hydrodissection, radial striations.

Occasionally hydrodissection is completed with just a single fluid bolus delivered at one location. Usually more than one injection is needed, and often at multiple sites. Probably the most efficient way to achieve complete subcapsular hydrodissection is to site the cannula at the 3 and then 9 o’clock positions via the main incision. Each wave then only has to pass around 180° in order for them to meet posteriorly and complete the hydrodissection. Also from each opposite location at either side, the wave passes partly superiorly to hydrodissect the subincisional sector, which otherwise can be troublesome.

Finally, before proceeding to phaco you should confirm that the nucleus rotates freely within the capsular bag. This can be done using the cannula but is easier using a hooked instrument such as the chopper or Sinsky hook that uses less posterior pressure. Be sure to rotate it at least 90° in order to be certain that there are no residual adhesions, otherwise you will have to separate them later using repeat hydrodissection. You are now ready to proceed to nuclear disassembly.