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

Figure 23.25

nucleus that is engaged in between the loop automatically comes out along with the loop.

With this the trisection of the nucleus is completed.

REMOVAL OF NUCLEUS HALF

After bisecting or trisecting the nucleus, removal of the nucleus half is by following method.

For Soft Cataract

Visco Expulsion (Figure 23.25)

This method is helpful for soft cataract. Two halves of the nucleus is separated by viscoelastic solution. Pass the viscoelastic cannula under the nucleus deep toward 6 o’clock position. Inject enough bolus of viscoelastic solution and due to positive pressure into the anterior chamber, the nucleus half moves towards the scleral tunnel. Simultaneously depress the posterior lip of wound with viscoelastic cannula. It expels one half of nucleus through incision. The viscoelastic cannula acts as sheets glide. It avoids prolapse of iris into the wound. It keeps the lips of wound open. The positive pressure of viscoelastic solution into the anterior chamber expels the nucleus through small opening of incision.

Align the second half of the nucleus to the center inject the bolus of viscoelastic and do the same maneuver as above and expel the second half of the nucleus.

Lensloop (Figures 23.26A to C)

Lensloop can be used for nucleus extraction. Rotate the nucleus so that the cleavage line points towards the right end of incision. Now hold the lensloop in the right hand and insert it under left half of the nucleus. With the left hand, lift up the corneal edge of the wound with

Figures 23.26A to C

fine forceps and keep the lensloop parallel to iris surface. Press the posterior lip of wound with heel of the lensloop and withdraw the same. This opens the wound like fish mouth and without exerting pressure on endothelium; the nucleus fragment is withdrawn along with lensloop.

Align the second half of the nucleus to the center with viscoelastic cannula and remove it by same method as described above.

For Hard Cataract

McPherson forceps (Figures 23.27A and B)

I found it most useful for hard nucleus. After division of nucleus into two halves, precisely separate each half of the nucleus by viscoelastic solution. Make the anterior chamber deep and pass the McPherson forceps into anterior chamber, to the sides and under nucleus. Gently hold the 2/3 of nucleus into the forceps without compressing the nucleus. Fish mouth the scleral incision, by lifting up the upper lip scleral incision with place forceps and press the lower lip of scleral incision with McPherson forceps. Pull the fragment of the nucleus out of the anterior chamber parallel to the iris plane, without exerting pressure on endothelium.

Align the second half of the nucleus to the center of anterior chamber and remove it by same method as described above (Figures 23.28A and B).

Figures 23.27A and B

Figures 23.28A and B

CORTICAL CLEAN UP

It is important to achieve complete cortical clearance. This ensures faster recovery of visual acuity. It reduces

postoperative uveitis, less chances of after cataract, better posterior segment visualization and long-term stable IOL.

Cortical clean up is done by following methods.

1.Visco expression

2.Bimanual irrigation aspiration

a.Manual

b.Automated.

Visco Expression

After the nucleus is removed, debris of epinucleus and viscous material fills the anterior chamber. Inject bolus of viscoelastic solution into the anterior chamber at 6 o’clock position and press the posterior lip of the wound with the cannula. This expels the remaining debris. Do these maneuver two or three times to remove maximum quantity of epinucleus and cortical matter.

Bimanual Irrigation Aspiration

Close chamber irrigation and aspiration has following advantages:

•Minimal endothelial damages due to deep and wellmaintained AC.

•Pushes the vitreous to the back, ensures safety of posterior capsule.

•Easy aspiration of cortex because of open and accessible capsular fornices.

•Protection against choridal hemorrhage.

•It hydrates the cortex which helps easy aspiration.

Bimanual Irrigation Aspiration (Manual)

Connect the anterior chamber maintainer to either side of the side port incision and connect it to the irrigating solution.

Take simco type aspiration cannula having silicon tube with needle hub. Connect it to 1 ml syringe for cortex aspiration. Start irrigation from one side and aspiration from other side. Due to close chamber, the anterior chamber will remain deep and the capsular fornices will remain open. Pass the aspiration cannula into the anterior chamber and aspiration is done by placing the tip of aspiration cannula in contact with cortex. Engage the cortex and move the tip of the cannula from periphery to the center. This removes the strip of cortex from the capsular bag. Aspirate the cortex in the center. Start aspiration first at sub incisional area so that the residual cortical matter prevents the collapse of capsular bag. Do repeated aspiration on one side and aspirate one half of the cortex.

Figure 23.29

Interchange the anterior chamber maintainer cannula and aspiration cannula and aspirate either half of the cortex as above.

Manual I/A has more advantages than automated I/A.

Advantages of manual I/A are, better flexibility, easy to learn, better safety margin and better surgeon control.

Bimanual Irrigation Aspiration (Automated)

I use automated bimanual irrigation and aspiration. Use two side port incisions for bimanual irrigation and aspiration. Pass irrigation cannula from one side and aspiration cannula from other side (Figure 23.29).

Irrigation

Attach 20 G irrigating cannula to the irrigating solution. The height of the bottle ranges from 70 to 90 cm. More the height of bottle more is the fluid entering the eye. There should be enough fluid entering the eye so that lens and iris do not move forward when the aspiration is set at maximum.

Aspiration

I use Simco cortex aspiration cannula. Normally I set vacuum to 100 to 125 mm of Hg. There are no specifications as for the height of bottle and level of vacuum. When enough amount of fluid entered to the eye, keep the aspiration cannula in the center and start increasing the vacuum. When the vacuum is at full set, there should be no collapse of AC and iris lens diaphragm

should not move forward. First aspirate the debris of lens matter and viscous into the AC and then aspirate sub incisional cortex. The remaining cortical matter acts as cushion and keeps PC away. While entering into the fornix keep the vacuum at low level. Engage the cortex at the tip of the needle and remove the strip of cortex from the fornix and bring it into the center. Now increase the level of vacuum and aspirate the cortex. By repeating this procedure, the remaining cortex is aspirated.

After aspirating one half of the cortex by aspiration cannula, interchange the side of cannula to aspirate other half of the cortex. During aspiration, cortex may block the tip of the cannula. Clean the tip of cannula by rubbing irrigation and aspiration cannula on each other without removing the cannula from the anterior chamber.

Set the vacuum at low level (approximately 10 to 25 mm of Hg) and polish the posterior capsule with edges of tip portion of needle. Make the cannula horizontal and polish the anterior capsule with vacuum. It removes cells from the anterior capsule.

Narrow aspiration tip is more effective for aspiration of small bites of cortex. Wider tip provides faster aspiration of large bites of cortex. But it has a tendency to capture iris, posterior capsule and can collapse of AC.

When aspiration port is wider, use minimum vacuum and vice versa. This avoids collapse of anterior chamber and minimizes PC rent.

Scleral rigidity and pressure of speculum determines the height of bottle and vacuum pressure on incision.

Disadvantages of Automated I/A …..

•Changing of bottle height is essential to alter the flow.

•Difficult to perform during learning stage.

•A sudden surge can rupture zonules or posterior capsule.

LENS IMPLANT

Inject viscoelastic in to the anterior chamber. Due to close chamber, it pushes vitreous to the back. The capsular bag fornices open widely and make the anterior chamber deep. This helps easy implantation of IOL in the bag. Implant 5.25 mm rigid IOL with overall diameter between 11.5 to 12.5 mm according to your choice. Irrigate anterior chamber with irrigating fluid to remove extra viscous. Do bimanual I/A to remove viscous and other debris. Cover the conjunctiva over scleral incision and press the posterior lip of scleral

Figure 23.30

incision and watch for any leakage. If leakage is seen, remove the speculum and inject fluid through side port incision and when there is no leakage, close the lid.

Intraocular Lens

I have designed a new foldable intra ocular lens for Small Incision Cataract Surgery. This new IOL has been awarded as “Best innovation and Scientific Research Work by Maharashtra Ophthalmological Society. It was also published at various national and international conferences.

Dr Anil Shah’s Foldable IOL (Figure 23.30)

The intraocular lens that are commonly used for implant surgery are smaller lens having optical diameter of 5.25 mm and overall diameter of 12 mm. As these lens are smaller, they have many disadvantages like decentration, glare formation, pupillary capture difficulty in night vision peripheral retinal examination is difficult. And PCO formation etc.

In human body, the natural lens is bigger and having optical diameter 12 to 13 mm. So our aim is make an IOL which is closer to the natural lens. The idea came in to my mind that if large nucleus is removed through small incision than why not to implant big IOL through small incision. For developing this IOL, I received “Innovation Award in Ophthalmology” by Maharashtra Ophthalmic Society.

Figure 23.31

I have designed a big foldable lens that is having optical diameter 7.5 mm and overall diameter 13 mm (Figure 23.31). The lens can be folded by McPherson’s forceps and introduced through small incision. The lens has large optical diameter so there are no chances of decentration, pupillary capture. The large lens is aspheric lens so there is no glare or difficulty in night vision. Due to large optics peripheral retinal examination for retinal surgeon. Also the anterioposterior size is more so the lens snuggly fit in to the capsular bag. Large area of contact of posterior surface of lens is to the posterior capsule, so there is no dead space. This prevents epithelial proliferation and the posterior capsule opacification. So this lens removes all the above drawbacks of smaller lens. This is the first biggest lens ever introduced through small incision (Figure 23.32).

COMPLICATIONS

I am practicing this type of surgery since last 10 years and I have operated more than 6000 cases.

With practice, one can easily overcome the initial difficulties. Following complications are to be observed.

1.Button hole of scleral flap: Shallow groove, thin flap and improper plane of incision can cause button hole of scleral flap. Meticulous attention during the procedure will minimize the complication.

2.Peripheral AC entry: The most common problem is accidental peripheral entry too close to the root of the iris into the anterior chamber. This results in frequent iris prolapse during surgery.

3.Inferior iridodialysis: If nucleus is not free floating in anterior chamber, its edges remains attached to iris. While engaging the nucleus into the bisector loop, it can also pinch the iris with nucleus. While pulling of the snare, it may cause iridodialysis. This was noticed in one patient and by releasing the loop of snare the complication was avoided.

4.Hyphema: If wire loop bisector is not completely closed, hyphema can occur during bisecting nucleus. The edges of wire loop can cause injury to inner wall of the scleral tunnel. This can be avoided by proper closing of wire loop bisector during bisection.

5.Transient corneal edema: Endothelial touch is possible when the loop is encircling the nucleus. Endothelial touch is minimized by following ways:

a.Generous use of viscoelastic solution to the sides, above and below the nucleus.

b.Prevent collapse of anterior chamber by minimum opening of the loop.

c.Modified snare developed by me also minimizes

endothelial damage.

During initial learning phase, few patients had occasional patches of coalescent guttate, straight keratitis and slight corneal thickening. This

edema quickly resolves and is not clinically significant.

However with experience the postoperative appearance of cornea is better than previous experience. The clinical study of large number of cases and postoperative appearance of better corneas during follow-up suggests that endothelial cell lose is minimal.

6.Difficulty in prolapsing nucleus: It occurs when the pupil is small and the nucleus is soft. Small pupil may cause difficulty when inferior pole is prolapsed. When the superior pole is prolapsed by the methods described, with the tip of the viscoelastic cannula, spin the superior pole of nucleus through the small pupil to prolapse the same.

7.Posterior capsule dialysis: This occurs as a result of excessive handling during prolapse the nucleus into the anterior chamber. Accidental spinning of capsular dialysis. To avoid this do every step meticulously.

8.Posterior capsular rent: This occurs when irrigating cannula is blocked by cortical matter and passed under the nucleus to prolapse it into the anterior chamber. To avoid this, check the flow of irrigation and remove the blocked cortical debris before using it.

SUMMARY OF STEPS

•Conjunctival fornix base incision.

•Limbal and episcleral cautery.

•Make scleral tunnel incision with partial thick straight or frown scleral incision of 5.5 mm in length with clear corneal incision.

•Make anterior chamber entry at this stage.

•Inject viscoelastic to make chamber deep.

•Make side port incision at right angle to the scleral tunnel incision, with 20 G disposable needle.

•With 26 bend needle, do can-opener capsulotomy or capsulorhexis.

•Make anterior side port incision exactly opposite.

•Enlarge the inner corneal incision with 11 number blade in clear cornea. Extend the incision on either side to produce clear cornea valve. Make inner length of incision larger than outer length.

•Do hydrodissection and hydrodelineation to make the nucleus free into the capsular bag.

•Bring the nucleus into the anterior chamber. Make it free floating into the anterior chamber

•Inject adequate viscoelastic around the nucleus.

•Bisect or trisect the nucleus with snare.

•Remove the nucleus fragments with suitable method.

•Visco express the epinuclear and cortical debris.

•Irrigate anterior chamber to remove nuclear debris.

•Do bimanual irrigation and aspiration and aspirate cortex. Interchange the port to aspirate the either half of cortex and sub incisional cortex. Do anterior capsule vacuum polishing and posterior capsule polishing.

•Inject viscoelastic solution into the anterior chamber through side port incision and make the capsular fornices open.

•Insert rigid 5.25 mm IOL in the bag.

•Remove the viscous by irrigation and aspiration. Cover the conjunctiva on the scleral incision. Fill the anterior chamber with irrigating fluid. Press the posterior lip of the scleral incision to check any leakage.

DISCUSSION

In comparison to other small incision cataract surgery techniques and phacoemulsification, this technique of nucleus division has several advantages. The modified snare that I have developed is cheap, safe, easy to prepare and easy to learn. The two holes at the tip of the snare is the unique feature of the snare which is nor seen in any other types of snare. One can make this instrument on their own. This is not a machine dependent technique. It avoids considerable expenditure and risk of machine failure.

It is easy to perform in all types of nuclei from soft to hard. The time required of the surgery does not very from case to case. Where as, in phacoemulsification, the time depends upon the type of nucleus.

So, I feel, a surgeon who is performing phacoemulsification must acquire this non phaco technique.

Here, I suggest that, with locally available material you can achieve best surgical results. You need not have to buy any costly instrument. The aim of this book is to achieve best result out of waste.

I feel such type of technique is need for our country and to suppress the phacomania.

INTRODUCTION

There are many techniques which are available for doing effective small incision cataract surgery. Many splitting techniques have been devised to guillotine a nucleus. Single strands of wire, or nylon or polypropylene have been in use for some time as has the single strand, tonsil type, snare.

The problem is that using a single looped snare does not work as holding the lens eccentrically leads invariably to the nucleus being irregularly cut. Naturally if one is to hold an oval object it has to be held at its equator. At any other place it is bound to slip, or will eccentrically leaving a small and a large fragment of the nucleus. The question was also how to split a lens into three parts, preferably equally. This is important as only then the nuclear fragments could be removed through a 4.00 mm incision without stressing the edges of the incision

What is the mystique of 4.00 mm?

It has always been the dream of any small incision surgeon to take a nucleus out of a ‘foldable IOL” incision without widening it. Astigmatism is always negligible through a small incision, and a 4.00 mm incision always seals by itself if the tunnel is made well. In addition once can use the Sclero-corneal tunnel incision which leaves the eye the next day, literally looking as if it is unoperated.

The answer to the problem is obvious. Have a dual splitter which would work simultaneously, leaving three fragments, each of which is smaller than 4.00 mm. The techniques in doing this procedure ranged from using choppers, splitters, both single sided and double sided, as well is using a wire.

Keiki R Mehta, Cyres K Mehta (India)

In an effort to have a really functional unit, a disposable splitter was designed using two strands of wire and a disposable needle. However the ability to use a double wire to split the lens into its component parts as not yet been explored to its full potential. In India, hard cataracts are the norm rather than the exception. Splitting a lens into two will not permit to the fragments of a hard nucleus to be removed easily through a 4.00 mm incision. It is for this reason that the concept of splitting a lens into three parts rather than two makes sense.

Double wire snare. The trisector: Manner of construction

A 20 gauge needle is cut off at the tip and the edges of rounded but maintaining a slight bevel as it permits easier entry into the eye. It is made by using two strands of 28 gauge flexible stainless steel wire threaded though a 20 gauge blunted disposable needle. Of the two loops of wire, one leg of each is entwined around the other. Thus the two loops which should be four strands are now converted to three strands. The end of the three strands is now threaded through the 20 G needle and the excess wire is looped around in the form of round loop so that it can be held easily in one hand while supporting the blunt needle with the other hand.

No viscoelastic is used in the needle as it did lead to the wire locking and not moving smoothly in the bore of the needle. It is important that the loops of the wire should be uniform and equal. The wire selected is a stainless steel wire which has a quantum of tensile strength and is the one which is normally utilised by the orthopedic surgeons as a fine wire gauge. Since it costs virtually nothing to make, a fresh unit of can be made just prior surgery, and discarded following its use.

Figure 24.1: The four wires constitute tow loops. Make them spread outwards

Figure 24.2: Loops extended. Note divergence

Figure 24.3: The four wires are knotted together and made into a small loop

Figure 24.4: Standard 20 guage , 1" length disposable needle selected

Figure 24.5: 4.00 mm incision is adequate. Measure it and mark it to achieve consistant results

SURGICAL TECHNIQUE

The surgeon has the option of utilizing either topical anesthesia if his level of skill and competence permits him to do so, or alternatively he can utilize a standard retrobulbar or a peribulbar block. The conjunctiva needs to be excised at the corneo-scleral junction, simple cautery to control the bleeding is carried out. Care must be taken that the cautery setting is not so high as to leave grey marks on the sclera. The incision is made in a semi arcuate fashion in the sclera and the dissection carried forwards till it enters the clear cornea. Making the incision in this manner permits a virtual zero astigmatism to be induced by this “smiling” incision.

Figure 24.7: Tunnel dissected till it extends almost 3.00 mm into the cornea

Figure 24.10: Rotate the lens out of the bag. Simply turn it over with a blunt rotator

Figure 24.12: Check the wire double splitter for proper action

Figure 24.13: Wire loops inserted in the semi retracted position to easily navigate the 4.00 mm opening

Figure 24.15: Gradually swung around till the loops now lie vertical

Figure 24.16: Pull the loops snug to hold the nucleus. Note the spread of the wire loops

Figure 24.14: The wire loops are allowed to circumambulate the nucleus. Note the loops are horizontal

Figure 24.17: Note how snuggly the nucleus is held. It remains immobile