Ординатура / Офтальмология / Английские материалы / Master's Guide to Manual Small Incision Cataract Surgery (MSICS)_Garg_2009

INTRODUCTION

There have been many developments in cataract surgery in past few years, phacoemulsification nowadays being the most widely used system in the occidental world.

Phacoemulsification has had a very long development period with a very high cost both economically and also as far as serious eye complications are concerned.

This method depends highly on technology and it is still dangerous in difficult cases and/or when carried out by inexperienced surgeons.

THE BEAUTY OF MANUAL SURGERY

Phacoemulsification and other methods all have a common aim: that is to reduce the size of the surgical wound for obvious reasons. Most surgeons in the developed world believe that the only way to perform Cataract Surgery is by Phacoemulsification but fortunately, alternatively, it is also possible, if properly performed, to work manually through a small incision.

We are dealing with a system:

•rather inexpensive in it’s many modalities

•not dependant on higher technology

•applicable where technology, is simply not available

•that keeps surgeons mind and hands active (something that is very often lost in the presence of excessive technology)

•that becomes of great help in the case of transition to Phacoemulsification because of making the surgeon familiar with manually dealing with different structures in the reduced space of the

anterior chamber, proving very useful when considering the different Phaco techniques.

The excessive role of technology in the developed world has resulted in young surgeons being unable to deal both safely and effectively with simple procedures such as suturing still required in many surgical situations: again high-tech dependency consequences. Mastering manual surgery is, in my opinion, still essential in allowing surgeons to develop surgical skills instead of being passive spectators by use of technologically developed procedures, thus possibly becoming confused, for whatever reason, if the technology fails. We must not forget that even when things go wrong, there is still an eye to be healed or possibly more importantly to be saved. It is at these times that a too technology dependent surgeon may possibly become blocked whereas a manually experienced surgeon should still be able to obtain a good result.

SURGICAL TECHNIQUE

Strategic Consideration

When approaching cataract surgery in a manual way there are, in my opinion, a few facts that become very important.

Having to perform cataract surgery through a small incision in a manual way requires a few strategic considerations to be safe, precise and effective. Having to work in the limited space of the anterior chamber (AC) surrounded by very delicate structures (Corneal Endothelium, Iris, Pupil, Chamber Angle) which have to be respected requires previous thought and consideration:

Surgical Wound

•Size as small as possible but with regard to previous astigmatism which can be dealt with both wound location and size.

•Location depending on Astigmatism (ideal result) and also facility of manipulation inside of the eye (safety)

•Valvulation important for AC stability during surgery and safety in the postoperative period.

Space Maintenance

Valvulation of the surgical wound and viscoelastic devices are the main items in this respect.

•Selection of viscoelastic device depends on:

—The eye condition

—Surgical technique

—Surgeon preference

—Need for protection of different eye structures

—Complete removal at the end of surgery.

Fragmentation

Size reduction of hard components of the Cristallin lens is always required to allow its removal through a small incision.

As this has to take place in the limited space of the AC surrounded by very delicate structures, a good idea is to work on the hard part made as small as possible: separation between the hard core of the lens from the cortex-epinucleus. This left - in – place cortex gives additional protection to the most delicate barrier to be respected: the posterior capsule.

Removal of Hard Fragments

It is simpler and less traumatic if removing two, three or four clean fragments. The wound construction becomes very important for this purpose.

Removal of Soft Components

It is much simpler if separation of hard – soft components has been carried out. There are many possible methods depending on the surgeons training or preferences.

Personal Technique

Specific Instruments

The very simple instruments we need to perform this technique are shown in Figure 15.1.

Figure 15.1: Specific instruments

•Nylon sling retractor. Originally designed by Keenan (stainless steel) and Quintana (surgical nylon). We modified the tip by giving a slight bend to facilitate fragmentation in different positions. If a surgeon works at a 12 o’clock position through a temporal incision this slight bend makes it easier to manipulate the nylon sling around the nucleus. Using fisherman’s nylon instead of stainless steel or surgical nylon is cheaper, less traumatic and more efficient. This nylon is more rigid than the surgical one making it easier to manipulate it around the nucleus to fragment it. If the nylon is less rigid usually more manipulation is required to bring it around the nucleus causing unnecessary damage to the iris or the endothelium.

•Synskey hook

•Modified small size irrigating vectis. It has been closed to act as a spoon the irrigation driven by the assistant helps maintaining the AC during fragment removal and helps extraction by slight overpressure in the AC.

Field Preparation

The usual one, no difference to common intraocular procedures.

Wound Construction

It can be either limbal or a scleral tunnel. A clear corneal approach means no advantages and makes fragment extraction more complicated and consequently traumatic.

If the wound is meant to be astigmatically neutral a scleral tunnel is the best choice. If, on the other hand, pre-existing astigmatism is to be corrected, a limbal approach should be considered.

In any case a good valve is very important to both contribute to AC stability during surgery as well as to ensure a quiet postoperative period and wound stability in the long run. A paracenthesis is performed to allow by manual manipulation.

Capsulorhexis

The anterior chamber has to be filled with viscoelastic to allow this manoeuvre. We use a standard viscoelastic device like Healon® at this stage. It is important not to overfill the AC because an increased pressure might lead to sudden AC decompression when manipulating with the instruments. This might result in a diversion of the Rhexis towards the periphery which might be difficult or even impossible to correct.

Size: Providing we are going to produce a clean separation between hard core and epinucleus, we don’t need a specially large Rhexis. Anything between 5 and 6 mm will be suitable for most of the eyes and also will provide an edge coverage of the IOL.

Staining required when difficult visibility is expected. In case of doubt it is better to stain than not to. Trypan glue is the material of choice.

Hydrodissection

It is performed in the usual way and should be as complete as possible. Overpressure should always be avoided by repeatedly depressing on the anterior face of the lens after injecting a small amount of BSS. An overpressure could easily end up in a posterior capsule rupture.

Hydrodelineation

We usually do it but it is not essential in our technique. Removal of the soft cortex situated in front of the anterior face of the hard core to allow access to a cleavage plane between the hard core and the soft cortex surrounding it.

Separate both hard core and soft matter To cleanly separate both hard core and soft matter a four hands maneuver (surgeon and assistant) is used (Figure 15.2). The surgeon holds a Sinskey hook with his left hand and a bent cannula connected to a assistant-driven infusion system in his right hand. By directing the cannula to

Figure 15.2: Four hands maneuver (surgeon-assistant)

the cleavage plane between hard core and epinucleus it is possible to fully disengage the nucleus from the epinucleus by injecting BSS all around the nucleus edge. Using both Sinskey hook and the bent irrigating cannula, it is possible to completely liberate the nucleus by injecting and rotating 360°. The bimanual action inside the eye is nearly 100% effective in obtaining this separation in every case (Figure 15.3A).

The nucleus is then brought up into the AC, (Figure 15.3B) leaving both epinucleus and soft cortex in place as an extraprotection for the posterior capsule. At this point a dispersive viscoelastic device like Viscoat® is injected between the nucleus and the posterior cornea to protect the endothelium.

Figure 15.3A: Hard core disengagement

Figure 15.4: Nuclear fragmentation with a nylon sling

Hard core fragmentation depending on the nucleus size, one, two or even three cuts with a nylon sling will be performed with the nylon sling to obtain two, three or four fragments (Figure 15.4). These cuts are produced by retracting the nylon sling which has been placed around the nucleus. We use Fisherman’s nylon rather than surgical nylon because of being more rigid and thus easier to manipulate around the nucleus. It is also much cheaper and there is a wide selection to choose.

Fragment extraction it is performed by sandwiching out the fragments by means of a modified closed irrigating

vectis and Sinskey hook, again by means of a four hands maneuver (Figure 15.5). Now the surgeon engages every fragment with both vectis and Sinskey hook and removes them from the AC. In the meantime the assistant pushes some fluid in the AC through the irrigating vectis to both compensate for the underpressure as the segment leaves the eye and help its removal. Of course overpressure should be avoided in any case.

Cortex removal: At this stage we have to deal with a fully preserved epinucleus and the soft cortex. To facilitate this maneuver BSS is injected between the posterior capsule and cortex to luxate it into the AC. The harder epinucleus can be easily removed by means of an oversized glass cannula by simple aspiration (Figure 15.6). The AC is maintained by gentle irrigation performed by the assistant at the wound site. The underpressure created in the AC by the aspiration will be compensated for by this irrigation without ever creating overpressure. The vacuum being created in the AC by the aspiration will automatically take as much fluid as required to maintain the AC shape.

Capsular rim polishing: Posterior capsule and anterior capsular rim polishing is carried out by means of a current irrigating polisher.

Lens implantation: after filling both capsular sack and AC with an easy - to - remove viscoelastic device the IOL will be implanted in the usual way depending on type of lens, etc.

Viscoelastic removal: it must be as complete as possible to avoid intraocular pressure elevations. Instead of an

irrigation aspiration system we prefer to flush out the viscoelastic by injecting BSS into the AC and depressing the scleral lip at the same time (Figure 15.7). We prefer to use a site port cannula which allows flushing behind the lens as well as gently irrigating different structures like corneal endothelium, AC angle where adherent viscoelastic might still be present.

Suture: Sutureless cataract surgery has become the fashion. In my view a few objections can be made to that generalised attitude. There is no doubt that a simple stitch adds safety to the immediate postoperative period. It is indeed more time consuming but in my view safety should come first. In the meantime the surgeon keeps practicing stitching which sometimes is so strongly required.

INTRODUCTION

It was probably in 1990 that we were shown the videos of Blumenthal’s technique. Many surgeons took an instant liking to the concept of ‘Hydrodynamic’ delivery of the nucleus. There has been no looking back since then. The band of followers of this particular technique has been steadily growing. As manual small incision cataract surgery (MSICS) gains more popularity, several techniques have emerged, only to be tried and discarded later. Blumenthal’s technique is among the few to have withstood the test of time. Perhaps because of it’s tremendous ‘replicability’. I mean that if the steps are followed correctly, there is no reason why every surgeon’s results would not be comparable. There also is a wonderful flexibility to the whole technique. Each surgeon can adapt or modify steps to suit his “comfort zone”. And adaptability with the times is a feature too. Initially doing it under peribulbar, Dr.Blumenthal himself is now performing this surgery under topical anaesthesia plus a little superior subconjunctival lidocaine.

My personal experience has been very rewarding. The quality of surgery that I was able to obtain in ECCE after 10 years, I could achieve the same in 1 year with Blumenthal’s technique.

PRINCIPLE

The principle underlying this technique is that BSS is the nearest physiologically to the natural aqueous humor, and it should be used under pressure to carry out all the surgical maneuvers in a close chamber surgery. The judicious use of the anterior chamber

maintaining system, using the anterior chamber maintainer (ACM) connected to a bottle of BSS elevated to the required height provides a comfortably formed AC for doing the procedure of cataract extraction and IOL Implantation. The nucleus delivery is BSS assisted, thereby removing the need to introduce any other instrument inside the eye. At no stage does the IOP rise beyond 40 mm of Hg, that too for brief periods of time. Use of Sheet’s glide makes delivery of the nucleus smooth and effortless. Because of a deeply formed chamber at all times, viscoelastic materials are not needed.

ANTERIOR CHAMBER MAINTAINER (ACM)

This is a very versatile instrument comprising of a canula 2.5 mm long, with 1 mm external diameter and 0.6 mm internal opening, with a beveled tip. It is slightly flattened, giving the lumen an oval shape. The tip is rounded, and not sharp, to prevent damage to the Descemet’s membrane or the endothelium. It is attached to a bottle of BSS via silicon tubing and IV Set. The height of the bottle should be adjustable for different steps in the surgical protocol. In my personal opinion, this instrument is to MSICS what Simcoe’s cannula is to ECCE. Except, perhaps that while Simcoe’s cannula can be used only for cortical aspiration, the ACM plays a pivotal role in ALL steps of surgery. The advantages of the use of ACM in different maneuvers will be highlighted at each stage in the following account, and again at the end.

We will now proceed step by step through the surgery, mentioning alternatives wherever required.

Always use an MVR blade for this. The 20G MVR will give you a side port able to comfortably take most of the instruments needed to be introduced inside, as well as an ACM port adequate for the 20 G ACM. Ensure that the blade is sharp, to avoid Descemet’s detachment. The side ports can be one or two, at 9.30 o’clock, and at 2.30 o’clock. Their length should be roughly 1mm intrastromal, to ensure self-sealing nature (Figure 16.1). The ACM port should be at 6 o’clock, directed horizontally (from Temporal to Nasal). The intrastromal length in this case should be 1.5-2 mm, to accommodate the ACM and keep it stable during surgery (Figure 16.2). The ACM is introduced without flow with bevel up. After it has entered the AC, the bevel is rotated down, and BSS flow is resumed (Figure 16.3).

CAPSULOTOMY

In the interest of In-the-bag placement of IOL, a CCC should be the aim in every case. But the technique is NOT rhexis dependant. In all MSICS techniques, one should aim for a 6-6.5 mm rhexis. Here, the BSS bottle should be raised to 70-75 mm to get as deep a chamber as possible, and as flat and relaxed an anterior capsule as possible. A standard 26G needle cystitome should be used, mounted on a BSS filled syringe. Optionally, this step may be undertaken with the ACM closed and AC filled with a viscoelastic material if that is more comfortable for the surgeon. I’ve found it much better

Figure 16.3: ACM fitting

to use the ACM. The advantages are as follows: (a) The capsular flap moves a little with the turbulence in the AC thereby making it easier to identify. (b) Cortex, if disturbed by the cyst tome, stays in its place instead of floating free in the chamber. (c) In hyper mature and Mortgaging cataracts, the milky fluid is either expelled from the side port, or can be aspirated with the same syringe, the fluid in the AC being instantly replaced from the ACM, without causing turbidity. In case the

Figure 16.4: Scleral incision

rexes runs out, one can easily convert to can-opener capsulotomy. The only problem, as I see it, may arise for those used to using forceps for CCC. Well, they will just have to learn to use a cystitome. Once the capsulotomy is completed, removing the capsular fragments is very easy. Most often, the fragment presents itself at the side port as the cystitome is being withdrawn. If not, a canula may be introduced to suck it out. Sometimes, a canula can also be used to “catch” the capsular flap and perform the rhexis after the initiation with a cystitome.

SCLERAL INCISION

A fornix based conjunctival flap is made, and underlying blood vessels cauterized with bipolar cautery.

The scleral incision is placed 1-2 mm behind the limbus. A horizontal 5.5 mm partial thickness groove is fashioned in a straight line. From the 2 ends of this, 2 cuts of 1-1.5 mm are made radially, i.e. directed towards the center of the cornea, but going away from the main incision into the sclera (Figure 16.4). A carefully handled Razor blade fragment can be as good as an expensive preset knife. The groove should be about half thickness of the sclera. In the unfortunate situation of accidentally going too deep, Uveal tissue will become visible, or may even bulge through. In that case, lower the bottle height or close the ACM, suture the wound, and try the same at a different location.

Figure 16.5: Scleral tunnel

TUNNEL AND INTERNAL OPENING

Using a sharp crescent blade, start the tunnel at any point along the horizontal incision (preferably at the center) and take it into clear cornea straight to about 2-2.5 mm, with a wriggling movement of the blade. Extend the tunnel on either side to include the sidecuts, by slightly angling the blade (Figure 16.5). Ensure that the corneal end of the pocket is larger than the outer, scleral end, and the inner edge is almost parallel to the limbus, i.e. it is crescent-shaped. This gives us a ‘pocket’ which is about 6 mm by 4.5 mm, with an internal end of about 7-8 mm (Figure 16.6). Make sure that the tunnel is uniplaner and adequate by once more sweeping the crescent blade through it. AVOID holding the Scleral lip of the tunnel with forceps at any stage. You may hold the neighboring limbal conjunctiva or subconjunctival tissue with an atraumatic forceps to stabilize the eyeball during this maneuver. Use of a SHARP crescent every time will reduce the drag on the tissues, and give you a smooth tunnel and a lesser astigmatism.

The Anterior Chamber is now entered from the center of the internal edge of the tunnel using a sharp keratome angled downwards, pointing towards the center of the pupil. As soon as the tip of the keratome becomes visible in the AC, the blade is made parallel to the Iris plane, and the entry completed. This is now enlarged in either direction, using the same instrument,

Figure 16.6: Diagrammatic sketch of incision and tunnel (a) scleral incision; (b) side pockets; (c) internal corneal opening

Figure 16.7: Enlarging internal opening

or switching to a blunt tip enlarging keratome. Remember to ‘cut’ only while entering, and not while withdrawing the instrument from the AC. If the keratome is angled to cut forward and sideways, you can fashion an internal opening which will be parallel to the limbus, instead of a straight line incision. Do not cut UPTO the limbus, but stop just short of it (Figure 16.7). This ensures a ‘true’ self-sealing incision, as well as helps in

reducing Postoperative Astigmatism. The presence of ACM gives you a turgid, ‘normal’ feeling eyeball, making it easy to do these steps. You may ‘experience’ the difference, by trying the tunnel and entry step in one case, with ACM off, and the eye filled with viscoelastic material.

It will be prudent to always bear in mind that this step, the designing of the Scleral-tunnel and the internal opening, will play a major role in giving you minimum Postoperative Astigmatism and a true self-sealing wound. Therefore, stick to using the best and sharpest blades, thereby ensuring sound sleep for you.

HYDROPROCEDURES AND NUCLEUS PROLAPSE

This step is best undertaken at this stage. I used to do hydroprocedures soon after CCC. The benefit was that it gives us a fair idea of the size of the nucleus before we start making our incision, thereby allowing us to tailor our incision size according to the nucleus. But very enthusiastic hydrodissection before opening the chamber has the risk of putting undue stress on the zonules, as well as on the posterior capsule. Also, in some cases, the nucleus immediately prolapses into the AC, increasing the risk of endothelial touch during Tunneling or wound enlargement. Hence, it is better to do this step at this stage. Also, it may be more prudent for the beginner to use a little viscoelastic material (with the ACM closed) to coat the endothelium at this point, before starting hydroprocedures. The ACM may then be opened. A small quantity of BSS from a syringe with an appropriate canula is now injected between the rim of the anterior capsule and the cataract till a ‘fluid wave’ becomes visible. The canula is now relocated by withdrawing, and reinserting obliquely into the soft cortex, till resistance is felt in the form of hard core of the nucleus. Again injecting about 0.5 ml of BSS will, hopefully, produce the ‘Golden Ring’, completing the separation between the hard-core nucleus and the epinucleus. Most often, with this, one edge of the nucleus ‘pops-up’ out of the capsular bag. This part of the equator of the lens is engaged gently with the tip of the cannula, and ‘cart wheeled’, to loosen the remaining attachments of the nucleus, and to induce it to prolaps out of the capsular bag. More gentle irrigation beneath this edge may be of further help. The aim is not necessarily to completely bring the entire nucleus into the AC, but only to ensure that the nucleus is indeed ‘free’. Also, to rotate the prolapsed pole of the nucleus to the 12 o’clock position (Figure 16.8).

Figure 16.8: Hydroprocedures and nucleus prolapse

Figure 16.9: Sheet’s glide

NUCLEUS EXPRESSION

The Sheet’s Glide is a transparent plastic strip, about 3-4 mm wide, 0.3 mm thick, and about 3 cm long, with rounded and smoothened tip (Figure 16.9). This is gently introduced in the eye through the tunnel, passing its tip under the up tilting pole of the nucleus, up to about 1/3rd of the way. The function of the glide is twofold. One is to guide the nucleus into the tunnel. The other is to provide a smooth surface for the ‘gliding’ nucleus.

Figure 16.10: Nucleus expression

Once the glide is in position, place the Mcpherson forceps tip just inside the tunnel, resting on the glide, and exert gentle pressure downwards. The nucleus will engage in the corneal end of the tunnel, thereby effectively blocking it, and reducing the outflow of BSS to almost nil. Further, continued pressure, will cause the nucleus to ‘shave-off’ epinucleus and mould itself into the tunnel till it is finally expelled in a gush of BSS (Figure 16.10). If necessary, after the nucleus engages, one can raise the BSS bottle height again to 70 cm, as had been done for CCC ( presuming that it had been lowered after CCC), to raise the expulsion pressure being exerted on the nucleus. Most nuclei, irrespective of color, size, and hardness, can be removed this way.

(The experience is akin to the normal ‘delivery’ of a baby.)

It is really very difficult to produce a PC rent with the glide unless one is very rough, or pushes the glide too far inside. One must aim at insinuating it just beneath the nucleus and advancing it a little. The direction of push should be towards the 6 o’clock position, and not downward.

In a few cases, the nucleus may engage in the tunnel, its pole may present itself at the scleral end of the incision, but the body of the nucleus may get stuck at the corneal end of the tunnel. In such cases, the nucleus can be engaged with the Cystitome, or the Sinsky hook, and gently dialed out. Either the whole nucleus will get dialed out, or a Pie-shaped piece will break from it. In that case, one can rerotate the nucleus so that the now reduced diameter engages and the nucleus is expelled.