Ординатура / Офтальмология / Английские материалы / Small Incision Cataract Surgery (Manual Phaco)_Singh_2002

right angle to the axis of lens and by cartwheeling the nucleus can be brought out. In case of large nucleus, a part of it can be sheared off with a needle. The nucleus is then pushed back in the AC, and rotated so that the smaller diameter is engaged, and the nucleus is delivered.

SECTION NOT TAKING UP NUCLEUS–CAUSES

1.Small section

2.Irregular section

3.Hypotony

4.Leaking AC

5.Iris prolapse before nucleus is engaged.

Solution

1.Re-evaluate the adequacy of section and enlarge with keratome if needed.

2.Raise the pressure of AC by lifting the irrigating fluid

bottle higher.

A thin iris repositor and even a 3.2 mm keratome can be used on place of lens glide for nuclear delivery.

Cortical Clean-up

We disconnect the AC maintainer at this stage and do cortical clean-up with cimcoe cannula.

IOL Placement

IOL is held by straight lens holding forceps at the junction of 1/3rd and 2/3rd of optic. The lower haptic and optic is guided into the bag at 6 O’clock position. Same forceps can rotate the upper haptics into the bag or a Y shaped dialer can be used to place the upper haptic into the bag. McPherson forceps is not a very good instrument for placing the IOL in the lower fornix of the bag (Fig. 22.5).

Closure of Section

A well-constructed inverted V or frown shaped incision can be left unsutured. Fluid is injected from sideport to see the leakage of section. If doubt about safety of the section exists, an ∞ (infinity) shaped suture, taking deep bites in the scleral bed, is applied. Sideport site and AC maintainer site can be hydrated by injecting a few drops of BSS in the stroma (Fig. 22.5).

FURTHER READING

1.Feil SH, Crandall AS, Oslon RJ: Astigmatic Decay following small incision, self-sealing cataract surgery: One year follow up, J Cataract Refract Surg 21: 433-36, 1995.

2.Jaffe N: Cataract surgery and its complications. CV Mosby Co.: St Louis; 6th ed. 1990.

3.Rainer G, Vass C, Menapace R et al: Long-term course of surgically induced astigmatism after a 5.0 mm sclerocorneal valve incision. J Cataract Refract Surg 27(12): 1642-46, 1998.

4.Rozakis GW: Cataract surgery: Alternative small incision techniques. Jaypee Brothers: India.

5.Shephard JR: Induced astigmatism in small incision cataract surgery. J Cataract Refract Surg 15(1): 85-88, 1989.

6.Singer JA: Frown incision for minimizing induced astigmatism after small incision cataract surgery with rigid optic intraocular lens implantation. J Cataract Refract Surgery 17(Suppl): 677-88, 1991.

7.Steinert RF, Brint SF, White SM et al: Astigmatism after small incision cataract surgery. Ophthalmology 93(4): 417-23, 1991.

8.Uusitalo RJ, Tarkkanen A: Outcomes of small incision cataract surgery. J Cataract Refract Surgery 24(2): 212-21, 1998.

9.Wright M, Chawla H, Adams A: Results of small incision extra-capsular cataract surgery using the anterior chamber maintainer without viscoelastic. Br J Ophthalmol 83(1): 7175, 1999.

Small incision cataract extraction without phacoemulsification has many advantages.

1.It is elegant.

2.It is not dependent on expensive and frequently capricious equipment.

3.The visual results compare favourably with those of any other available technique.

4.The cell count of the corneal endothelium, after surgery also compares favourably with that of other techniques.

5.It is virtually impossible to drop the nucleus into the vitreal cavity.

6.The continual inflow of Balanced Salt Solution (BSS) through the Anterior Chamber Maintainer (ACM) reduces the risk of infection.

7.The same flow militates against expulsive haemorrhage and eliminates the need for any other kind of irrigation.

My method combines elements of manual phacosection as made popular by Peter Kansas and the socalled mini-nuc approach of Michael Blumenthal. The procedure starts with three self-sealing paracentesis openings, made in the peripheral cornea with a 1.15 mm stiletto knife. The first, lower temporal, angles obliquely to point towards the inferior pole of the lens.

The other two enter at ten O’clock and two O’clock, angled to point just above the centre of the lens.

The lower canal will hold the ACM (first described by Lewicky) and must be precisely the width of the knife. Any sideways movement of the blade, particularly during withdrawal, will produce an incision too large and likely to permit leakage around the ACM.

Inserting the ACM

The tubing must be full of BSS and free of air bubbles. A three way tap, proximal to the ACM tubing allows control of the fluid flow into the eye without the sudden surges that occur with an automated foot switch.

The 20 gauge ACM is held, bevel downwards, at right angles to the surface of the cornea. The tip of the bevel is then insinuated into the paracentesis. Continued pressure at right angles engages the ACM in the corneal tunnel. At this point, it is moved into the line of the tunnel and, with an oscillating rotatory action can be moved into its final position with the tip of the ACM inside the anterior chamber (AC).

The bevel of the ACM must be rotated to direct the fluid flow away from the corneal endothelium (Fig. 23.1).

Fig. 23.1: (Chawla) Wound and paracentesis incisions

The ACM must be at least 20 gauge. Some manufacturers produce ACMs whose too small bore does not allow an adequate flow of fluid. The use of such products might well have led to a distrust of the ACM technique.

Irrigation

BSS is obligatory to maintain corneal clarity. The bottle height should be as low as is compatible with the maintenance of the AC. A height of fourteen inches corresponds to an Intraocular Presssure (IOP) of 26 mm/Hg.

The surgeon should be aware of the fluctuations in IOP created by changing the bottle height.

Incision

The corneo-scleral incision must be self-sealing of the ACM is to be allowed to maintain a constant AC depth.

I use a 15 blade, a crescent knife and a 3.2 mm keratome. For the dextrous, it is possible to make all these incisions with the 15 blade-again reducing the cost.

An external incision, 5.2 mm long is made just behind the limbus to be between one-third and one-half of the scleral depth.

A scleral pocket is created and extended 1.5 mm into the cornea with the crescent knife.

The AC is entered from the anterior end of this pocket with a 3.2 mm keratome. The internal edge of this wound is parallel to the limbus and is made by cutting in one direction only-not with a saw-like movement. Making the internal wound slightly wider than the external creates a natural birth canal to collect lenticular fragments for smooth delivery.

Capsulorhexis

At this point the fluid to the ACM is turned off at the three way tap and visco-elastic is introduced into the AC through a cystotome. Creating a continuous curvilinear capsulorhexis calls for a skill that is common to all cataract techniques but here the diameter must be slightly bigger than standard in order to allow delivery of the endonucleus or the combined endo-and epi-nuclei into the AC. If the capsulorhexis is thought to be too small then as a last resort, it can be relaxed by oblique incisions with long Vannas scissors at three and nine O’clock.

Trying to achieve the desired shape of the capsulorhexis under BSS calls for a skill that is denied to most of us.

Nuclear Dislocaton

Fig. 23.2: Rotation of nucleus

If the combined nuclei threaten to be too large for the capsulorhexis then one should endeavour to isolate and dislocate the endonucleus (Figs 23.2 and 23.3a to c).

There is no hard and fast rule about this but in my experience, removing the epinucleus from the capsular bag is easier when it is still attached to the nucleus. When it is on its own, it can sometimes be a reluctant passenger. But that is still a safer alternative to sacrificing an intact capsulorhexis.

Nuclear Bisection

The instruments essential for this technique are-

1.The solid vectis-a flat plate attached to a handle not unlike a hockey stick with the blade pointing upwards.

2.The nuclear bisector-a firm cutting implement similar in shape to a lens dialler but without the angled tip.

Once the endo-nucleus or the combined nuclei are isolated they can be dialled into the AC. The space between them and the corneal endothelium is filled with visco-elastic through a Rycroft cannula. Now is the time to divide the nucleus in two between the solid vectis and the nuclear bisector. The critical point of all these manoeuvres is that every time one enters the anterior chamber, one must precede this entry with visco-elastic. No matter how much is used, its use will be fully repaid by a crystal cornea the next day and a gentle reminder that this operation is still significantly cheaper than phacoemulsification.

The aim is to insinuate the solid vectis between the nucleus and the capsular bag and the bisector between the nucleus and the cornea. The technique is to begin with the bisector and then tease the solid vectis into position whilst advancing the tip of the bisector until it is pointing from eleven or one O’clock towards six O’clock.

As with golf clubs, the right handed and the left handed operator can be accommodated (Fig. 23.4a and b).

Figs 23.5a and b: Fragments of nucleus being removed by Arruga forceps

Although the temptation might be to press the bisector down towards the iris, the secret is to keep the bisector firm whilst pressing up, away from the iris with the solid vectis, to split the nucleus easily into two.

The half nuclei are now ready for removal. There are several methods for achieving this end but I have found the best is to modify the tips of the standard Arruga intracapsular capsule forceps (Figs 23.5a and b). If one thinks of them in their natural state as being tipped with “teaspoons” then we must convert these into a “soup” spoon shape.

Again preceding every move with visco-elastic to the AC, one dials the half nucleus so that it lies directly in line with its proposed line of removal. The forceps are slid into the AC and the trick is to lay them nearer the iris so that the fragment appears to be nipped upwards rather than grasped directly. It is the simplest matter now to slide it out, remembering always that the leading pole must be elevated so as not to catch on the wrong side of the scleral tunnel.

Removal of Epi-nucleus

any floating fragments to be swept into the tunnel and out of the eye. A nucleus, too soft for bisection can be removed in the same way.

Cortex Aspiration

A cortex extractor with a 0.4 mm port attached to a 5 ml syringe easily removes the remaining cortex through one or other of the side port incisions.

Lens Insertion

The implant can be dialled into the capsular bag in the standard way under visco-elastic which must be removed afterwards.

Closing the Wound

The wound can be left sutureless but in my experience this will produce up to three dioptres of astigmatism. A 10/0 Mersilene suture in the style of the St. Andrew’s cross goes a long way to minimise postoperative astigmatism. So fine a gauge of suture material cannot be tied against resistance without breaking. Such resistance can be elegantly and briefly eliminated by having the assistant squeeze the inflow tubing to the ACM. With the wound edges in the correct position and the second throw of the knot about to be drawn tight, the tubing is released and a gentle tide of BSS rises to meet the counter pressure of the completing knot.

Removal of the ACM

No great complexity is required to disengage the ACM from its corneal tunnel, or to realise that the AC will shallow somewhat during this manoeuvre.

Sealing the Paracenteses

BSS from a syringe can be injected through a Rycroft cannula into the walls of the tunnels, producing opaque blanching of the stroma and restoring the AC depth as deemed appropriate.

With the pressure being high in the syringe a little foresight will make sure that the Rycroft cannula does not turn into a bullet leaving a trail of devastation across the anterior segment.

Pitfalls

Corneo-scleral Tunnel not Self-sealing

obstruction be insurmountable, then excision of the offending iris is often the only recourse.

Occasionally partial closure of the three way tap can reduce the tide of BSS flowing through the wound.

A third possibility is to conduct as much of the operation as possible under visco-elastic, thus minimises damage to the iris.

After this operation is complete, in such circumstances, the iris sometimes defies all atempts to replace it where it belongs. At this point the cortex extractor can be turned to another use and, through one of the side ports, can, by suction, pull the iris out of the wound and into an approximation of a round pupil.

Extra sutures can help to keep it in place but it must be remembered that every time a susture is inserted into a leaking wound with the three way tap of BSS open, the iris will be swept out again remorselessly.

Failed Capsulorhexis

The surgical dilemma is common to all techniques. If the integrity of the posterior capsule is felt to be threatened, then the flow of BSS must be carefully monitored during cortex extraction.

Even with an intact capsulorhexis, it is sometimes possible to capture the posterior capsule in the port of the cortex extractor. The risisng stress lines cannot be mistaken and reversal of the flow almost always saves the capsule and the reputation of the surgeon.

Too Small Capsulorhexis

The temptation here is to preserve the continuous curvilinear state at all costs. To succumb to this temptation risks converting to the operation we have all abandonedthe intracapsular cataract extraction.

The endo-nucleus refuses to float on a sea of BSS out of the capsular bag because the exit to the AC is too small. A search for the nuclear margin will almost certainly find the capsule instead and the sudden case with which everything enters the AC tells again the story of the road to perdition being paved with good intentions. An intact posterior capsule which can be achieved often, with a little extra care is worth the sacrifice of the curvilinear edge.

Reluctant Epi-nucleus

The flow of BSS constantly drives the iris into the tunnel, obstructing any attempt at surgical elegance. If the

Occasionally the epi-nucleus defies all attempts to tease it out of the capsular bag. The simplest way to overcome

its reluctance, is to reduce the inflow of BSS where upon the semi solid rolls and layers of epi-nucleus will rise into the AC sufficiently to allow the tip of the cortex extractor, without suction, to dial the remainder out of the capsular bag rather like a mollusc out of its shell.

Postoperative Care

This differs in no way from any other technique and the eye is optically stable almost from the outset.

Anatomically Shallow Anterior Chamber

It would be self evident that endothelial protection can only be achieved by increased use of visco-elastic.

INTRODUCTION

Current surgical techniques used in cataract surgery have two fundamental objectives: (i) to induce the minimum postoperative astigmatism, and (ii) to achieve rapid recuperation of the patient’s sight after surgery.

To meet these objectives, it is necessary to perform cataract surgery using a small incision. It has been shown that the smaller the surgical incision, the smaller the residual postoperative astigmatism.

Of all the techniques described for cataract operations, phacoemulsification is the one that allows working with smaller incisions. However, it is a technique which requires a long learning curve, with expensive and complicated instrumentation and equipment.

Our manual multiphacofragmentation (MPF) technique allows cataract surgery through 3.2 mm clearcorneal or 3.5 mm scleral-tunnel incisions. In this method the nucleus is fragmented into multiple tiny pieces of 2×2 mm.

The method enables cataract surgery in soft and hard nuclei. The results obtained in postoperative astigmatism are similar to those obtained with phacoemulsification, but with a shorter learning curve and less financial outlay.

On the other hand, our method is an ideal back-up after discontinuation of emulsification when complications arise in phacosurgery, since with the help of our instrument set, we can conclude the surgery without enlarging the incision.

We designed an instrument set, manufactured by John Weiss and Son Ltd in England, which consist of:

•A racquet-shaped nucleotome 8 mm long and 2 mm wide, divided along its short axis by 3 thin transverse bars 2 mm apart , set at 45 degrees to a long straight handle (Fig. 24.1).

Fig. 24.1: Nucleotome with a racquet-shaped end

•A spatula 8 mm long by 2 mm wide the same shape as the nucleotome, used as a support during the fragmentation (Fig. 24.2).

•Two straight-handled manipulators, right and left, used to collect the nuclear fragments (Fig. 24.3).

SURGICAL TECHNIQUE

This technique can be carried out with the use of retrobulbar or peribulbar anesthesia, topical or topical + intracameral anesthesia.

Fig. 24.3: Manipulators, right and left

To perform MPF it is important to have good pharmacological mydriasis, since the pupil could contract during surgery.

Anterior Capsulotomy

High density viscoelastic is injected into the anterior chamber (AC) through a superior and temporal paracentesis, and a capsulorhexis is performed with a cystotome. It should be sufficiently wide (6.0 - 6.5 mm) to allow an easy luxation of the nucleus into the AC.

Fig. 24.5: The 3.5-mm scleral-tunnel incision is made with the help of an angled crescent knife

Hydrodissection and Luxation of the Nucleus

After entering the AC with a 3.2 mm phaco knife, balanced salt solution (BSS) is injected through the incision with a Binkhorst cannula between the anterior capsule and the cortex at 12 O’clock, or with a straight Rycroft cannula. The BSS must be injected slowly and continuously until the “wave of dissection” is visible on the posterior capsule.

The injection of BSS is continued until luxation of the nucleus in the AC is partial. Then, it can be completed by rotating the nucleus with a cannula, cystotome

or spatula.

Nuclear Fragmentation

Once the nucleus has been luxated into the AC, highdensity viscoelastic (Viscoat, Amvisc Plus, etc.) is injected into the surrounding area to fill the AC. The nucleus is then fragmented by placing the spatula beneath and the nucleotome on top of the nucleus (Fig. 24.6). Pressure is then created by slowly pressing the nucleotome against the spatula, until this section of the nucleus is fragmented into four pieces which remain within the nucleotome, and which, with the help of the spatula, are extracted from the AC with a “sandwich” technique (Fig. 24.7). This maneuver is repeated until all the nucleus is fragmented.

During nuclear fragmentation it is important to fill the AC with high-density viscoelastic, as needed, to protect the corneal endothelium and to facilitate safe manipulation during surgery.

Fig. 24.7: The nuclear fragments within the nucleotome are extracted with a sandwich technique

nucleotome. Otherwise they can be extracted by the nucleotome and spatula, by aspiration with a Simcoe or Charleux cannula, or by gentle irrigation of the AC with BSS using a Rycroft cannula while simultaneously depressing the posterior lip of the incision.

IOL Implantation and Wound Closure

High-density viscoelastic is injected into the capsular bag and a foldable IOL is implanted (Fig. 24.9). The viscoelastic material is then aspirated with an irrigating/ aspirating cannula. Closure of the incision is performed with stromal hydration, or with a single cross-stitch (Fig. 24.10).

We recommend to ophthalmologists who are new to this technique that they initially practise it using incisions of more than 3.2 or 3.5 mm and thereafter reduce the incision size once they have mastered the technique.

Lately I have been performing some steps of my technique with the help of an anterior chamber maintainer (ACM)—model Lewicky 20 G from Katena or the ACM 20 G from John Weiss Ref. 0185061.

The ACM works by producing a constant irrigation flow of BSS into the AC. This flow generates a positive intraocular pressure (IOP) that stabilizes the AC depth during some steps of the surgery. On the other hand, with the ACM the quantity of viscoelastic material used per surgery is reduced, diminishing the financial outlay.

The ACM is used:

•During the capsulorhexis

•In order to aspirate the anterior cortex and epinucleus in soft and medium hard nuclei before the hydrodissection/hydrodelineation

•For the aspiration of cortical debris

•For the extraction of tiny nuclear fragments, by depre-

ssing the posterior incision lip with a straight cannula. The maneuvers of nuclear multi-fragmentation and IOL implantation are carried out with the help of high

density viscoelastic material.

REFERENCES

1.Uusitalo RJ, Ruusuvaara P, Jarvinen E et al: Early rehabilitation after small incision cataract surgery. Refract Corneal Surg 9:67-70, 1993.

2.Shepherd JR: Induced astigmatism in small incision cataract surgery. J Cataract Refract Surg 15:85-88, 1989.

3.Cristobal JA, Minguez E, Ascaso J et al: Size of incision and induced astigmatism in cataract surgery. J Fr Ophtalmol 16: 311-14, 1993.

4.Gutierrez-Carmona FJ: Manual technique allows for small incision cataract surgery. Ocular Surgery News: Surgical Maneuvers 15(21):14-15, 1997.

5.Gutierrez-Carmona FJ: Manual technique allows for small incision cataract surgery. Ocular Surgery News: Surgical Maneuvers (Internat ed) 9(2):10-11, 1998.

6.Gutiérrez-Carmona FJ: Nueva técnica e instrumental de facofragmentación manual para incisiones esclerales tunelizadas de 3.5 mm. Arch Soc Esp Oftalmol 74:181-86, 1999.