|Year : 1989 | Volume
| Issue : 2 | Page : 69-72
57, Joshi Colony, The Mall, Amritsar, India
57, Joshi Colony, The Mall, Amritsar
|How to cite this article:|
Singh D. Extracapsular surgery. Indian J Ophthalmol 1989;37:69-72
| Introduction|| |
In recent years, extracapsular surgery has been assuming increasing importance. The main reason has been the advent of intraocular lenses. Extracapsular surgery is mandatory with most of the popular designs of intraocular lenses. An intact posterior capsule ensures greater confidence in implant introduction and its fixation. Extracapsular extraction is advisable when operating on the cataracts of high myopes, since this procedure offers greater protection to the retina. Extracapsular extraction is also useful for dealing with cases of traumatic cataract. The cataracts of infants and children are impossible to remove by intracapsular method, hence the need for extracapsular technique.
While intracapsular lens extraction techniques are few and well understood, the extracapsular methods are extremely varied and more or less self-developed because of a myriad of factors like the type of training received, the types of instruments used, the type of illumination and the type of magnification used. For these reasons, the description will be largely individualistic to the author. Some ophthalmologists might find a couple of points in the technique worth incorporating in their own surgery.
THE AIM OF EXTRACAPSULAR SURGERY:
The aim of extracapsular surgery is to remove the anterior capsule in a desired way, and to delivery the nucleus and the cortical matter, without causing damage to the endothelium, the posterior capsule and the zonular fibres. The iris stroma and the posterior pigment epithelium should be minimally handled. The incision line should be well sealed.
USE OF MAGNIFICATION AND ILLUMINATION:
The ideal magnification is 6, but less than 4 X is not advisable. A good loupe should have a wide field and should be prismatic. Keeler 6 X or Carl Zeiss 6 X are excellent loupes. Excellent coaxial light is available with Carl Zeiss Loupe. Many Indian microscopes with coaxial or oblique illumination are available. The magnification need not be more than 6 to 7 X for doing extracapsular surgery. I have worked with Mentor and Carl Zeiss OP 99 microscopes with coaxial illumination, but my present preference is a 6 X loupe aided with a hand held light made by Punjab Surgical Company. The advantage with a hand held light is that you can direct the light from any desired angle, to bring contrast and increased visibility of the tissues. This helps in clearly visualizing the cortical matter and the capsule all the time.
INSTRUMENTS NEEDED FOR EXTRACAPSULAR SURGERY:
We use the following instruments :
Blade holder, Lim's forceps, curved corneal scissors, needle holder, 27 gauge disposable needle, irrigating cannula, Singh's blast cannula, Singh's irrigation/aspiration cannula, 30 ml. disposble syringe, 1 ml. disposable syringe, 2ml. syringes for air and carbachol and 50 micron stainless steel sutures.
A good incision is half the operation. I personally abhor the idea of making a conjunctival flap and cauterising innumerable blood and aqueous channels at the limbus. My preference is for an incision on clear cornea which is available nearest to the limbus. In cases having filtering blebs, the incision has to be made far more anteriorly. In cases of microcornea, the incision shifts outwards to allow easier passage of the nucleus.
The size of the incision: The size of the incision depends upon a number of factors - the age of the patient, the type of cataract, the expected size of the nuclear mass to be delivered, the intention of implanting an intraocular lens and the design of the intraocular lens. As a general rule, an incision erring on the liberal side causes less problems during surgery. I use stainless steel blade fragments for my surgery.
How is the incision made? I hold the limbus from near 11'o clock with a Lim's forceps. A small vertical nick is made at the 12' o clock limbus. It has two functions: It acts as a marker for accurate suturing. Secondly it tests the quality of the blade fragment. If the blade fragment appears rough, it is changed. The incision, about half the thickness of the cornea, placed vertically, starts from near 3 o'clock and reaches near 9 o'clock. As the blade reaches near the 11 o'clock position the incision is progressively deepened, so as to open the anterior chamber in the end. So this last part of the incision will be purely vertical in profile. Some aqueous gets drained out. At this stage, the anterior chamber is filled with 2 % methylcellulose. This serves three purposes :, Firstly the iris falls back so that the chance of inadvertent cutting of the iris, when completing the section, are minimized. Secondly, anterior capsulotomy becomed easier, because of a fair depth of the anterior chamber. Thirdly, the endothelium is afforded some protection during the extraction of the nucleus-cortex mass and during irrigation/aspiration. The section is completed with a sharp scissors from 9 to 3 O'clock. The second part of the incision is made oblique. A blunt scissors is likely to put tension on the endothelium and Descemet's membrane and might even start a retroflexion.
We do an anterior capsulotomy with the help of a disposable 27 gauge needle. The needle tip is bent towards the bevel like the beak of a parrot. The needle shaft is bent at 70 degrees, about 10 mm. from the tip. This anterior capsulotomy needle is connected to an irrigating handle which in turn is connected to balanced salt solution through the tubing of the drip set.
The balanced salt solution bottle and the drip set are autoclaved the evening before surgery.
We make the irrigating handle from a 2 ml. disposable syringe. The rubber part of the piston is separated from the rest of the piston. An eighteen gauge needle is passed through the rubber and this combination is then pushed into the syringe. The advantage of this plastic disposable irrigating handle is that the various types of cannulas can be mounted more confidently.
We like to irrigate slightly while doing anterior capsulotomy. At the start of the procedure, the tip of the cystitome is introduced into the anterior chamber for half a millimeter and kept there for a few seconds. The fluid from the cystitome fills up the anterior chamber. Now is the time to do the capsulotomy.
The most usual form of anterior capsulotomy in our country is what is called a can-opener capsulotomy. This is done as follows : As soon as the anterior chamber fills up with fluid from the irrigating cysttome, we start opening the periphery of the anterior capsule. It is started at 11 O'clock and the surgeon moves in an anti clockwise direction (this is what I do, you can go in the opposite direction if you like). An eye is kept on the tip of the needle to see that it does not get under the capsule. When the postal ticket like fenestrations are formed all round, it is time to pull out the capsular flap. The flap is freed bit by bit from the lower side and is pulled out by the curved tip of the needle.
Throughout the procedure of anterior capsulotomy, we have to make sure that the tip of the needle should remain extremely superficial and cut only the capsule. If it dips into the cortex, the whole procedure goes out of control. Besides the nucleus may get displaced at this inauspicious time, or this may cause a tear in the zonule and prepare the ground for lens displacement and vitreous presentation. The aim of my anterior capsulotomy will be just an anterior capsulotomy without any other disturbance.
At this point, I might stress that a mistake committed at any time of extracapsular procedure will complicate the following steps of the operation. Therefore we should attempt to do each step meticulously. Remember, a step well done is time saved.
Any instrument that is introduced into the eye should press on the posterior edge of the incision and not rub against the edge of the cornea, which in practice means corneal endothelium and Descemet's membrane.
If the capsular flap tears in parts during extraction, the remaining parts may be cut with a long scissors or caught with a forceps and pulled out. Usually the presence of the lens nucleus prevents you from doing this work cleanly. That means this step may have to be postponed, till the nucleus has been removed.
In Morgagnian cataracts, the anterior capsulotomy should be done in a straight line from 6 O'clock to 12 O'clock. Even doing this little thing may be difficult because the fluid leak takes away all the support that the capsulotomy needle normally gets from the cortex. In intumescent cataract again, the cortex starts leaking into the anterior chamber and prevents a planned anterior capsulotomy.
DELIVERY OF THE NUCLEUS-CORTEX MASS
All authors talk of nucleus delivery, but I talk of nucleus- cortex mass, that is the nucleus + perinuclear cortex. The extent of perinuclear cortical mass will vary from much to nothing, depending upon the size and colour of the nucleus. There is nothing to talk about in Morgagnian cataracts. Similarly there is not much to talk about in dark brown cataract; if you can remove the nucleus, you have removed almost everything of the cortex. We have to talk of the immature, the posterior subcapsular, the near mature and somewhat hypermature cataracts. In all these cases there exists a nucleus, perinuclear cortex and subcapsular cortex.
The delivery of the nucleus-cortex mass is effected with fluid pressure, mediated through a special instrument Singh's blast cannula. This instrument is fashioned out of an 18 gauge needle. The bevel of the needle is shortened and it is somewhat flattened. The cannula is bent at about 70 degrees about lcm. from the tip. It is introduced flat into the eye, so that the direction of fluid flow is always downwards and forwards. The cannula is connected to the irrigating hand piece. The fluid should flow in a steady stream.
Two instruments are used during nucleus-cortex mass delivery - the blast cannula and a forceps. The forceps is pressed at the 12 O'clock limbus to raise the upper edge of the nucleus. The blast cannula can also sometimes be used to lift the upper edge of the nucleus. This is done by actually introducing the cannula into the anterior chamber, placing it on the anterior surface of the mass and giving it a downward push (irrigation through the cannula is on at that time). The forceps pressure at 12 O'clock and blast cannula action can go hand in hand.
It should be remembered that some of the methylcellulose that was used to fill the anterior chamber at the beginning of the procedure is still lying in the anterior chamber. If you want to give greater protection to the endothelium, you may fill up the anterior ch.amber. Now the blast cannula is turned on and the fluid is directed under the upper edge of the nucleus-cortex mass. This mass gets lifted almost instanteously. The stream of fluid is now directed towards the side of the mass, usually the right side in my case,. The mass starts delivery and the delivery is very precipitous. Sometimes the mass hesitates to move out. In that case some fluid is pushed from one end of the incision line, into the anterior chamber. The fluid mass on both sides of the nucleus-cortex mass, push the latter out. This delivery, effected by hydro-dissection, leaves some cortical matter inside the eye (the subcapsular cortical matter). The Cannula blasts the cortical matter, off the surface of the posterior capsule and capsular fornices, thus making it easy for the irrigation/aspiration cannula to perform effeciently, as described below.
A lot of things can go wrong, if the blast cannula is used improperly
a. Retroflexion of Descemet's membrane.
b. Fluid migration behind the posterior capsule, through some area of ruptured zonule, leading to intraoperative hard eye.
c. Rupture of the weakened or diseased posterior capsule.
d. Tumbling of the nuclear-cortical mass, instead of upper edge delivery,
e. Excessive irrigation causing damage to the endothelium.
During the delivery of the nucleus- cortex mass the endothelium is protected by methylcellulose already present in the anterior chamber and by irrigating fluid that separates the mass from the endothelium.
I have made calculations that show that 30 % of the endothelial cells reside in the outermost 1 mm circular strip of endothelium. One half of it, that is 15 % reside in a 1 mm strip along the incision line. I call this strip the golden strip. Trauma to this golden strip should be minimized to reduce the loss of endothelial cells.
IRRIGATION/ASPIRATION OF CORTEX
There are various ways of dealing with the residual cortex. In some cases it may be possible to just wash out' the cortex without any aspiration. My design of I/A cannula (Singh's I/A cannula) is the only one of its kind that has a downward facing irrigation and upward facing aspiration port. This arrangement has a number of advantages : The irrigation on the underside keeps the posterior capsule away from the cannula, thus avoiding direct instrumental trauma to this delicate structure, Further this downward and forward direction of fluid jet lifts the cortex from the surface of the posterior capsule and from the fornices. The upward facing aspirating port ensures that at no time during aspiration, the posterior capsule will be caught and torn. The combined action of irrigation and aspiration removes the cortical matter. One need not go under the iris to pick up cortical matter. The cortex is attracted towards the aspirating port like a magnet, by the unique fluid dynamics obtained by this design of the I/A cannula.
The irrigation/aspiration process is complex and the complexity varies from patient to patient, depending upon the space in the anterior chamber, the size of the pupil, the consistency of the lens matter and its intimacy to the posterior capsule and the fornices.
The I/A process is also greately influenced by the rate of irrigation and aspiration. The optimum has to be found by experience. For irrigation, we use a 30 ml. syringe held by the assistant, who is keenly watching the depth of the anterior chamber. He sees to it that the chamber does not collapse at any time. Excessive irrigation will drive the cortical matter away from the aspiration port. Collapse of the anterior chamber during aspiration will lead to the posterior capsule striking the cannula and getting ruptured.
I like to do aspiration with an extremely smooth 1 ml. disposable tuberculin syringe. This small volume syringe endures that there will be no sudden collapse of the anterior chamber.
I have used Cavitron irrigation/aspiration machine for cortical clean up, for about a year. I can say with confidence that nothing can beat the supercomputer control of your mind and your fingers, which react instantly the way the occasion demands.
MANAGEMENT OF THE POSTERIOR CAPSULE
The capsule shows the following appearances at the end of cortical clean up:
a. A smooth clean, well stretched posterior capsule.
b. A few lens fibres still sticking to the surface of the well stretched capsule.
c. A plaque on the well stretched capsule.
d. A wrinkled clean posterior capsule.
e. A wrinkled posterior capsule with few fibres sticking. f. A wrinkled capsule with star like figure or figures. g. A wrinkled posterior capsule with a big plaque.
The cleaning of the capsule with an irrigation cannula, polishing it with a Kratz scratcher or a primary posterior capsulotomy will depend upon a number of factors like the age of the patient, presence of myopia, history of retinal detachment in the other eye or the eye under operation, presence of silicone oil in the posterior chamber, history of cystoid macular oedema in the other eye, history of proliferative diabetic retinopathy, the tenseness of the eye under operation and the experience of the surgeon.
We like to clean those posterior capsules that are well stretched. If a plaque is covering only a part of the pupil and the rest is very clean, no interference is necessary. If there is a big plaque on a well stretched capsule, the plaque is pulled out with the tip of a needle most of the times without disturbing the anterior vitreous face.
The plaques in the eyes of children may be left alone for secondary capsulotomy, as primary posterior capsulotomy usually causes vitreous presentation. The wrinkled capsules may be dealt with by a primary posterior capsulotomy in the presence of a plaque or a star like figure.
How much should one polish the posterior capsule? Just short of rupturing it.
For me, a peripheral iridectomy is a must. This is a precaution for the future when you might have to perform a posterior capsulotomy, at which time the vitreous might block the pupil and lead to glaucoma.
CLOSURE OF THE INCISION LINE
No amount of excellence in extracapsular surgery is of any use if the closure of the incision line is substandard, allowing leakage of the anterior chamber, iris prolapse or iris incarceration. We like to make a fool proof closure with 9 to 12 sutures with 50 micron stainless steel.
| Conclusion|| |
There are many many thoughts that come to the mind when you are actually operating and facing certain situations. That multitude of situations is too difficult to tackle here. For example : How would you do extracapsular surgery in a subluxated lens (Marfan's syndrome) or how would you perform extracapsular surgery where you suspect a pre-existing rupture in the posterior capsule. Or how would you complete extracapsular surgery when you are facing a posterior capsule rupture when most of the lens matter is still inside.
And then the problem in our country, where over 7 million people have to live as blind, since no help is forthcoming. Extracapsular surgery will slow down the process of surgery for some time, but might, a big MIGHT catch up. This `might' brings in a fear to my mind that microscope assisted surgery, with costly microinstruments and disposbles, or semidisposables, the lack of in-house or nearby facility for cheap YAQ - laser capsulotomy will bring in many new dimensions of problems in times to come. The surgeons must learn doing an excellent posterior capsulotomy for after cataract. The surgeons should not completely throw away their knowledge of intracapsular surgery. The institutions, in their efforts to catch up with extracapsular surgery, should not forget to teach good intracapsular surgery. Our country needs intracapsular techniques for decades to come. The closure of the incision line needs great attention at this moment of Indian ophthalmology.