Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001

Shrikant Kelkar

Capsulorrhexis:

Principles and 11

Advanced Techniques

ANTERIOR CAPSULORRHEXIS History

The problems related to the sulcus implantation of posterior chamber intraocular lenses (PC IOLs) during the period of about 1975 to early 1980s lead to the idea in favor of placing the intraocular lens implant into the capsular bag which lead to a better centration of the implant. The new design of Simcoe loops (modified C loop) improved better centration. However decentration was not uncommon. The analysis of this decentration showed that in spite of the fact that the lenses were in correct endocapsular situation tears of the anterior capsule originated, luxating one loop into the sulcus which was considered a precondition for subsequent decentration. Realizing the above difficulty in the centration of lens the idea of continuous curvilinear capsulorrhexis (CCC) was born. The credit goes to Tobias H Neuhann and his brother Thomas in developing the technique of capsulorrhexis. At the same time totally independent development by Howard Gimbel who was working on the same idea called this technique as “continuous tear capsulotomy”. Finally, Neuhann and Gimbel called their development continuous curvilinear capsulorrhexis which soon gained popularity all over the world.

Physics of Capsulorrhexis

If we consider a strip of paper to be torn into two pieces it can be done in two ways: one is as shown in Fig. 11.1A—what can be considered as shearing technique or Fig. 11.1B—ripping.

CAPSULORRHEXIS: PRINCIPLES AND ADVANCED TECHNIQUES 105

Figs 11.1F and G: Capsulorrhexis by ripping technique: Dot indicates point where the tear is held with the forceps

image of the area of capsulorrhexis performed so far and its edges will indicate in which direction the capsulorrhexis will proceed. Figure 11.1E shows one-third of the rhexis completed. Take a note of the point at which the instrument engaged the capsule which has remained 2 to 3 O’clock hours away from the point of

(n) shearing. Instead if the instrument was placed to say at point m, an artificial stress line would be created that would compromise the predictability of the direction of shear. In shearing technique the flap must be spread out flat otherwise it would convert the shear to modified rip.

Capsulorrhexis with Ripping

Figures 11.1F and 11.1G demonstrate the ripping technique. The surgeon must note that the direction of pulling is much more towards the center of the capsule and the flap is engaged by pulling the instrument at a point which is much closer to the tear. The ripping technique has the tendency to extend peripherally. It has been found that ripping techniques are more difficult to control and are more likely to extend peripherally compared to shearing technique. Yet one must know its ability in changing the direction of the tear.

Initiation of Capsulorrhexis

The capsule can be incised at point a, proceeding to point b. The triangular flap thus created is grasped at point c and drawn in the direction of the arrow in a curvilinear fashion. Shearing forces will be equally acting at point b and d.

In Figures 11.1H and I the pulling motion has changed to a curvilinear direction shown by the arrow. Figure 11.1J shows its further progress.

CAPSULORRHEXIS: PRINCIPLES AND ADVANCED TECHNIQUES 107

Integrity of the zonules In order to avoid damage to zonular fibers the capsulotomy should be performed carefully in the pre-equatorial zones.

Aperture The aperture must be wide enough to allow emulsification of the nucleus easily. A large capsular aperture facilitates easy and quick aspiration of the cortical material. At the same time it should not be so wide as to allow the nucleus to prolapse into the anterior chamber during hydrodissection procedure which usually happens in grade I and grade II cataracts and hence between 5 mm and

6 mm is the ideal size of capsulotomy.

Shape If we consider the shape of the eyeball as a round clock, the movement while doing the capsulotomy should be like a radiating arm moving in a circular fashion. Similarly the opening should be round. Last but very important aspect is to have continuous margin. The advantages of the continuous margins are:

•Correct centration of the lens in the bag.

•The edges of the incision are strong and elastic enough and reduce the risk of capsuler rupture extending to the periphery which can happen in a canopener technique.

Principles

To achieve the above results the surgeon has to keep in mind the following principles: One must keep in mind before proceeding to surgery that any mistake made during this procedure may face subsequent problems.

•It is desirable to use high magnification so that surgeon can control every step of the procedure, adjust the sight and width of the incision and avoid traction process as and when possible.

•The light beam must be angled to provide good red reflex of the fundus.

•The intensity of the microscope light must be sufficient to facilitate clear view of the capsule and the red reflex.

•The pupil must be widely dilated which makes it easier for the surgeon to perform capsulotomy; small pupil can bring contact between cystitome and iris. Dilated pupil also facilitates good red reflex.

•A deep chamber reduces the risk of endothelial and iris damage hence the depth of the chamber must be maintained during the entire capsulotomy procedure. The high molecular weight viscoelastic substances are the best tools for this.

•One should keep in mind the attachment of the zonuler fibers. On the safer side the capsular aperture should not extend more than 3 mm peripherally

from the center of the anterior pole of the lens.

•The shape and size of the capsulotomy must be planned by the surgeon prior to beginning the capsular aperture.

•The entrance of the instrument into the anterior chamber must be well planned. One must keep in mind the anatomical variations of the individual eye like myopia, hypermetropia, etc. Thus it is desirable to have an optimal working

108 THE ART OF PHACOEMULSIFICATION

position with respect to the planes of the anterior capsule and the iris. Correct use of the instrument and the released hands of the surgeon makes

the job easier. The forceps or the cystitome must be handled gently and carefully. They must be used on the surface of the capsule with practically no pressure applied on the cataractous lens. The surgeon must avoid touching the iris because every such touch can reduce the size of the pupil. The surgeon must keep in mind that in younger patients the capsule is thin and elastic and the capsulotomy tends to extend easily towards the equator. Any time surgeon anticipates the difficulty he should stop what is being done and inject the viscoelastic substance to deepen the chamber which allows him a greater margin for maneuvers and errors.

Advantages of CC Capsulorrhexis

Intraoperative Advantages

•CCC limits the risk of tears extending to the periphery and to the posterior capsule during surgery especially in young patients.

•Hydrodissection becomes safe and easy.

•It restricts the intraocular turbulence inside the capsule.

•Reduces the stress on the zonules during surgery.

•Most important is that it allows easy aspiration of the cortex and does not

let any anterior capsular tags get caught into the aspiration port.

•It permits the correct positioning of the IOL in the bag because the surgeon has excellent view of capsular rim. Last but the most important is that since the rim is can be stretched even a slightly large lens can also be manipulated with a comparatively small capsular opening.

Postoperative Advantages

•Due to extensive contact area between the loop of the IOL the anterior capsule the possibility of decentering is reduced.

•Not being in contact with the ciliary body pigment dispersion, hyphema and inflammation are reduced.

•In the presence of ruptured posterior capsule after doing anterior vitrectomy

a large optic diameter lens can be inserted over the anterior capsule.

•Since the lens is put in the bag there is no need to use miotics or the need for iridectomy. It also avoids pupillary capture.

Difficulties during Rhexis

Rhexis Escape

In some cases while the procedure of capsulorrhexis is proceeding on the aperture goes on increasing towards the periphery. The moment this happens the surgeon must ensure that the chamber is adequately deep by injecting more viscoelastic

substance. It is advisable to use a cystotome attached to a viscoelastic syringe so that in case the chamber becomes shallow more viscoelastic can be injected into the chamber immediately. The chamber will deepen and the tendency for the rhexis to extend will be minimized. At this moment the flap should be caught close to the point in the capsule, the surgeon should then extend controlled pressure directed towards the center of the pupil.

Alternative to this technique, instead of forceps or needle one can take deeply

curved scissors, deepen the anterior chamber with the viscoelastic and cut the capsule with scissors at the escape point and redirect the opening back to the

initial route.

One can also choose a new point to start rrhexis in another position operating in a counterclockwise direction and try to join to the first rrhexis escape point.

In spite of these maneuvers if the rrhexis extends, abandon the idea of continuous capsulorrhexis and continue with can-opener capsulotomy.

Capsulorrhexis in Special Cases

Pseudoexfoliation The surgeon must be aware that in this condition the capsule is fragile so the opening must be small so that it does not reach the zonules or create traction forces. Such a small opening can subsequently be extended after the insertion of IOL or subsequently by YAG laser.

Young Patients In very young patients proper pupillary dilatation is a big problem. In addition reduced scleral rigidity increases the tendency to positive vitreous pressure. This leads to loss of control in the direction of capsulotomy with an increased risk of peripheral escape. In children therefore the initial incision must be small which can be better controlled by forceps than needle. Viscoelastic substances must be kept in hand.

Hypermature or Intumescent cataract Capsulotomy can be done easily when the red reflex is seen. In such situations like hypermature cataract there is no red reflex so capsulotomy becomes extremely difficult as there is no perception of the capsular flap. In addition when the cataract is swollen there are more chances of peripheral escape because of the greater tension on the anterior capsule.

When the cataract is intumescent, the contents are usually very liquid like milk, it is advisable to let the semiliquid cortex escape through a central incision, this should be removed with I/A and chamber should be filled with viscoelastic substance, the flap must be taken under a high magnification with very high illumination. This is a good indication to use forceps instead of needle. Instead of red reflex illumination it is advisable to use high intensity oblique illumination. Some surgeons prefer air in the anterior chamber instead of viscoelastic substance. It is advisable to use cystitome instead of forceps when the air is injected into the anterior chamber. Black cataracts also pose the same problem. In small pupils it is advisable to use viscoelastic to deepen the anterior chamber. Use of iris hooks or bimanual stretching is also recommended.

110 THE ART OF PHACOEMULSIFICATION

POSTERIOR CAPSULORRHEXIS

Posterior capsulorrhexis is a linear continuous circular capsulotomy with all the advantages of elasticity, stability and long-term resistance. This procedure is done in children which avoids second surgery or YAG laser. The surgeon proceeds in the same way as in the anterior CCC. The phacoemulsification is carried out, the anterior segment is filled with viscoelastic substance, the bag is also filled with viscoelastic substance. The first step is to perforate the posterior capsule. Viscoelastic is again introduced behind the posterior capsule which can prevent vitreous prolapse. The second step is to carry out posterior CCC with needle or forceps. In some cases when the vitreous prolapses anteriorly, vitrectomy is done. The remaining tyre like capsular residue provides the stable and secure site for IOL fixation. This posterior capsulorrhexis done in pediatric cataract surgery can avoid secondary membrane formation.

Disadvantages of CCC

The introduction of capsulorrhexis has led to a new problem called capsular shrinkage syndrome or capsular phimosis. This problem is observed more frequently in patients suffering from pseudoexfoliation syndrome, uveitis, retinitis pigmentosa, in combination with polymethylmethacrylate (PMMA) or silicone IOL implantation. All the above mentioned diseases have reduced number of zonular fibers as common observation.

Special Techniques

•Fluorescein blue light assisted capsulorrhexis for mature cataract.

•Staining the capsule with indocyanine green for white cataracts.

•Trypan blue capsule staining for better visualization in capsulorrhexis.

•Diathermy capsulotomy.

Trypan Blue Staining

When retroillumination is absent, e.g. dense cataract, it is difficult to discriminate the anterior capsule from the underlying lens tissue and capsulorrhexis carries a high risk of radial capsule tears.

To overcome this difficulty and better visualization of capsulorrhexis during surgery, one can utilize: (i) use of side illumination, (ii) hemocoloration of the capsule with autologous blood, and (iii) staining the capsule with gentian violet 0.1 percent or methylene blue 1 percent. All these procedures are relatively time consuming and require an adjustment of the surgical technique and may have endothelial toxicity.

On the other hand trypan blue stain enables the surgeon to visualize the capsulorrhexis in the absence of red reflex and does not affect the endothelium. Before injecting the dye anterior chamber is injected with air, removing the aqueous through the cannula. Trypan blue, 0.1 ml in a conccentration of 0.1 percent in

CAPSULORRHEXIS: PRINCIPLES AND ADVANCED TECHNIQUES 111

phosphate buffered sodium chloride is applied to the anterior capsule. After few seconds anterior chamber (AC) is thoroughly irrigated, viscoelastic substance is injected into the AC (Fig. 11.1K). Because of the blue stain the outline of the capsulorrhexis is easily visible. There is an additional benefit that the peripheral anterior capsule ring remains stained and clearly visible during phacoemulsification.

Diathermy Capsulotomy

In order to overcome the difficulty in doing capsulorrhexis under circumstances such as mature cataract and absence of red reflex, many surgeons use diathermy capsulotomy. One must keep in mind that some fundamental research from

Denmark showed that the extensibility of the capsule edge after diathermy capsulotomy was reduced to half than that of the CCC technique as done by needle or forceps. It was also noticed that the breaking force required to break the diathermy capsulotomy was one-fifth of that required to break the CCC edge. So, the surgeon must keep in mind the risk of inadvertent capsule opening subsequently by tearing during phacoemulsification or on implantation of IOL.

C O N C L U S I O N

Every surgeon dreams to provide greatest degree of stability of vision to his or her patients. In other words, the surgeon tries to restore the patient’s vision very close to the normal healthy eye without glasses. The new technique of CCC has introduced a biggest breakthrough in performing small incision or phaco surgery.

The most important advantage of continuous capsulorrhexis is that it holds the nucleus down in the bag during phacoemulsification surgery. It makes the surgeon keep the instrument tip in the bag and work on the nucleus. The second advantage is, it helps to maintain intact capsular bag. The circular opening into the anterior capsule opens the window over the nucleus. The structural rigidity and integrity of the capsular bag are almost identical to a completely intact bag. In the can-opener technique, the purpose was to permit the nucleus to get out of the bag while CCC holds the nucleus inside.

The principle of capsulorrhexis is well established now and its technical performance is being refined and advanced everyday. Capsulorrhexis is a fundamental surgical principle. These days the ophthalmic instrument manufacturing companies are bringing out many tools for the maximum comfort of the individual surgeon. Stability of the capsular bag and centration of IOL by this technique make emmetropia possible.