A System of Operative Surgery Part 34

[Ill.u.s.tration: FIG. 105. IRIDOTOMY BY ZIEGLER'S METHOD. Showing the first incision and the position of the second.]

[Ill.u.s.tration: FIG. 106. IRIDOTOMY BY ZIEGLER'S METHOD. Final step; the triangular flap of iris attached at its base is turned downwards.]

Apart from being one of the stages of removal of a cataract, already described, it is performed as an independent operation in the following conditions:--

1. For optical purposes (optical iridectomy).

2. For the relief of glaucoma, primary and secondary (glaucoma iridectomy).

3. For small growths at the free margin of the iris.

4. For prolapse of the iris through a wound.

OPTICAL IRIDECTOMY

=Indications.= Iridectomy for optical purposes is performed for a centrally situated nebula of the cornea and in some very rare cases of small central opacities in the lens. In the latter condition it is rarely of much value, as nearly all the rays which enter the eye pa.s.s through the central portion of the lens. Further, in this condition the lens may be removed and better sight obtained with gla.s.ses. Optical iridectomy should always be performed opposite a clear portion of the cornea, the lower segment of the eye being chosen, otherwise the coloboma may be subsequently covered by the upper lid. The site of election for the operation is downwards and inwards, but in all cases the patient should be carefully examined in the following ways: (1) the vision is tested, any refraction being corrected without a mydriatic; (2) the pupil is then dilated, and the best situation for the iridectomy determined by means of a stenopaic slit. The vision must be definitely improved by the use of these before operation can be advised. The disadvantage of an iridectomy is that it allows more light to enter the eye, and, if the periphery of the lens be uncovered, spherical aberration may result. For both these reasons, therefore, it is advisable to make the iridectomy as small as possible. Tattooing of the central scar in the cornea will often diminish the amount of light entering the eye, but before undertaking the latter operation, the eye should be cocainized and the area covered with a piece of black paper to see if the vision is improved thereby.

[Ill.u.s.tration: FIG. 107. OPTICAL IRIDECTOMY. The incision being made with a keratome.]

=Instruments.= Speculum, fixation forceps, bent broad needle or small keratome, Tyrrell's hook, iris forceps, scissors, and spatula.

=Operation.= The operation is usually performed under cocaine.

_First step._ The eye is fixed by grasping the conjunctiva directly opposite the spot at which the incision is to be made. The incision is then made by means of a keratome or bent broad needle directly behind the limbus, and enlarged laterally if desired (Fig. 107).

_Second step._ A Tyrrell's hook, bent at the correct angle, is pa.s.sed on the flat into the anterior chamber. When the margin of the iris is reached the handle is rotated and the hook is made to engage the free border of the iris, which is then withdrawn from the wound; a small portion is removed with scissors, which should be held at right angles to the wound when dividing the iris (Fig. 108).

[Ill.u.s.tration: FIG. 108. OPTICAL IRIDECTOMY. Method of removing the iris to produce a small coloboma.]

_Third step._ The iris should be carefully replaced and the pupil kept under the influence of eserine until the anterior chamber has re-formed, when atropine should be subst.i.tuted.

Care must be taken to see that the Tyrrell's hook presents no sharp angle, and great care is required in its manipulation, otherwise the lens capsule may be damaged, and traumatic cataract will result. If the iris slips from the grasp of the Tyrrell's hook, iris forceps should be used, the iris being grasped near its free margin and as small a portion as possible withdrawn.

=Brudenell Carter's method.= The ordinary optical iridectomy divides the sphincter iridis and so inhibits the activity of the pupil. With the idea of obviating this, Brudenell Carter removed a small portion of the iris (b.u.t.ton-hole), leaving the pupillary margin intact. On the whole the results of the latter operation are no more satisfactory, and the operation is more dangerous to perform owing to the likelihood of wounding the lens, and to the fact that monocular diplopia occasionally results.

The pupil should be under the influence of eserine. The incision is made as in the previous operation. De Wecker's iris scissors are inserted open into the anterior chamber, closed, and the piece of iris which bulges up between the blades cut off; this can usually be withdrawn with the scissors; or if not, it should be removed subsequently by forceps.

[Ill.u.s.tration: FIG. 109. OPTICAL IRIDECTOMY. Showing the coloboma.]

GLAUCOMA IRIDECTOMY

=Surgical and pathological anatomy.= The fluid in the anterior and posterior chambers of the eye is secreted from the ciliary body by a process of modified filtration. The fluid pa.s.ses partly direct into the posterior chamber and partly behind the suspensory ligament of the lens, making its way forward into the posterior chamber through the fibres of the suspensory ligament. From the posterior chamber it pa.s.ses into the anterior through the pupil; from the anterior it filters at the angle of the anterior chamber through the ligamentum pectinatum into the ca.n.a.l of Schlemm; thence it is carried into the blood-stream by the venous anastomosis in that region (Fig. 110).

The essential change found in all cases of primary glaucoma is the blocking of the angle of the anterior chamber owing to the root of the iris being applied to the back of the cornea, and thus preventing the filtration of the fluid into the ca.n.a.l of Schlemm, as a result of which the tension of the eye is raised, either acutely (acute glaucoma) or slowly from time to time (chronic glaucoma) (Fig. 111). The aim of every operation for the permanent relief of glaucoma is the opening up of Schlemm's ca.n.a.l at the angle of the anterior chamber or the creation of a new lymph channel between the anterior chamber and the subconjunctival tissue (filtrating cicatrix). Although this latter condition is not unattended by the risk of the spread of inflammation from the conjunctiva to the interior of the globe, it is not an inadvisable condition to obtain in some cases of chronic glaucoma if the scar be small and free from iris tissue; in this disease the opening up of the ca.n.a.l of Schlemm by iridectomy is often impossible. (See Sclerectomy, p. 231.)

=Indications.= Since the days of von Graefe, who first performed iridectomy empirically for the relief of glaucoma, the operation has held the first place in its treatment.

(i) =In primary glaucoma.= Iridectomy should be undertaken as early as possible in the disease. _In acute cases_, unless the tension is relieved, the disease ends in rapid destruction of the sight. Operation should always be undertaken as quickly as possible, provided the patient has not lost his perception of light for longer than about ten days.

[Ill.u.s.tration: FIG. 110. THE NORMAL ANGLE OF THE ANTERIOR CHAMBER.

A. Cornea.

B. Ciliary processes.

C. Iris.

D. Ciliary muscle.

E. Pectinate ligament, to the right of which is the angle of the chamber.

F. Ca.n.a.l of Schlemm.

G. Lens.

H. Posterior chamber.

I. Anterior chamber.

Whilst waiting for the operation, the pupil should be put under the influence of eserine (2 to 4 grains to the oz.) with the idea of reducing the tension by contraction of the pupil. Some surgeons, in addition to using eserine, perform a posterior scleral puncture with the idea of temporarily reducing the tension and allowing the acute symptoms to subside, and do the iridectomy some twenty-four to forty-eight hours later. This method is extremely useful (_a_) in cases where a general anaesthetic is inadvisable, since the reduction of tension allows cocaine to diffuse into the eye; (_b_) in cases liable to subsequent intra-ocular haemorrhage, a more gradual reduction of tension being obtained, rupture of a choroidal vessel is less likely to occur; (_c_) a deeper anterior chamber is often obtained, and hence there is less risk of wounding the lens during the operation; (_d_) in cases where the operation has been performed in one eye and the lens has been subsequently extruded on the dressings.

_In chronic cases_ early iridectomy is desirable, since the root of the iris applied to the posterior surface of the cornea becomes atrophic, so that when an iridectomy is performed the iris tears off at the anterior part of the atrophic portion, leaving the angle of the chamber still occluded by its root (Figs. 112 and 113). It is especially in these cases that a filtrating cicatrix, which sometimes follows iridectomy or sclerotomy, is desirable, and indeed some surgeons (Herbert and Lagrange, see p. 231), have recently performed operations with this idea in view, and it is probable that this operation or cyclo-dialysis will prove to be of use in these cases.

Operation is only contra-indicated in a few very rare cases in which the tension is controlled by the use of eserine.

(ii) =In congenital glaucoma (bup[h]thalmos).= In this affection the results of iridectomy vary. Without doubt, the tension has been relieved by iridectomy in some cases, and either this operation, sclerectomy, or cyclo-dialysis should be tried if the disease be not too far advanced.

(iii) =In secondary glaucoma.= For obvious reasons the predisposing causes should always be taken into consideration. Thus it would be of no use to perform an iridectomy in the case of a growth in the choroid. On the other hand, an iridectomy would be unjustifiable for soft lens matter in the anterior chamber, which merely requires evacuation. An early iridectomy in cyc.l.i.tis is not likely to influence the course of the disease favourably; at the most a paracentesis is required. As the early stages of cyc.l.i.tis may give rise to tension, it is essential that every case of glaucoma should be examined for kerat.i.tis punctata before operation.

[Ill.u.s.tration: FIG. 111. THE ANGLE OF THE ANTERIOR CHAMBER FROM A CASE OF RECENT GLAUCOMA. Showing its occlusion by the base of the iris, A, being adherent to the posterior surface of the cornea, so preventing filtration of the aqueous into the ca.n.a.l of Schlemm, B.]

In iris bombe and total posterior synechiae an iridectomy is indicated more to re-establish the communication between the anterior and posterior chambers than to clear the angle, and therefore it need not be so extensive. In cases of iris bombe where iritis is still present, and in cases of cysts of the iris, transfixion is all that is necessary.

It is very doubtful if iridectomy in glaucoma following thrombosis of the central vein is justifiable, for as a rule the tension is not permanently relieved thereby. In secondary glaucoma following cataract extraction or anterior synechiae, division of the capsule or the anterior synechiae will often relieve the tension.

=Instruments.= Speculum, fixation forceps, Graefe's knife (with a short, stiff, narrow blade), iris forceps, scissors, and spatula.

=Operation.= With the idea of opening up the angle of the anterior chamber by removing the iris as near its root as possible, the incision should be made somewhat further back behind the corneo-sclerotic junction than in cataract extraction. At the same time, if the incision be placed too far back the ciliary body is liable to prolapse into the wound. The old idea of opening up the ca.n.a.l of Schlemm by dividing it has been abandoned, as to do so would certainly result in prolapse of the ciliary body; and even if this did not happen, no good would result, since the ca.n.a.l would become closed subsequently by cicatricial tissue.

[Ill.u.s.tration: FIG. 112. THE ANGLE OF THE CHAMBER IN A CASE OF CHRONIC GLAUCOMA. The iris, A, has become atrophic at its root. An iridectomy in this case would not free the angle of the chamber, as the iris would separate at the point A.]

Although von Graefe used a keratome for making the incision, most British surgeons of the present day use a Graefe's knife, as it gives an incision that is less shelving and more irregular, thus predisposing to the formation of a filtrating scar; a good conjunctival flap is obtained with it and there is less risk of wounding the lens.

When performing the iridectomy it is practically impossible to cut the iris with scissors at its attachment to the ciliary body, and it is better to rely on tearing it off from the ciliary body, as it is in this situation that the iris is thinnest and most likely to give way, provided it has not become atrophic by prolonged contact with the cornea.

In acute cases and in cases of secondary glaucoma where there are many adhesions a general anaesthetic is desirable.

_First step. The incision._ The position of the surgeon is as for cataract extraction. The eye is fixed by grasping the conjunctiva close to the limbus downwards and inwards. If the patient be under an anaesthetic, two pairs of fixation forceps should be used, one being held by an a.s.sistant. Occasionally in glaucoma the conjunctiva tears very easily, and in these cases scleral forceps are of use, or, if the knife be already in the eye, grasping the insertion of the superior or inferior rectus. The Graefe's knife should be directed downwards and inwards towards the point of fixation, the point being pa.s.sed through the sclerotic 1.5 mm. behind the limbus to the outer side. Directly the anterior chamber is entered, the handle is depressed towards the patient's chin. The knife-point is kept superficial to the iris and is pa.s.sed very slowly across the anterior chamber, close to its periphery until the position of the counter-puncture is reached. The counter-puncture should be situated about 1 mm. behind the limbus in a direct line with the original puncture. Care must be taken in making the counter-puncture that the knife-point does not slip back on the sclerotic and so emerge further back in the eye than is desired. The knife is then made to cut out upwards and a good conjunctival flap is obtained. The incision should be carried out slowly, so that the aqueous escapes gradually, as sudden reduction in the intra-ocular tension is liable to lead to intra-ocular haemorrhage.

[Ill.u.s.tration: FIG. 113. IRIDECTOMY FOR GLAUCOMA. Failure to relieve the tension owing to the iris not tearing off at its junction with the ciliary body, due to atrophy from prolonged contact with the cornea.]

_Second step. The iridectomy._ The iris forceps are inserted closed into the anterior chamber, opened, and made to grasp the iris near the periphery (Fig. 114) towards the side of the wound on which the iris is first to be divided; then with a slight side-to-side movement of the forceps the iris is withdrawn from the wound until its peripheral attachment to the ciliary body, near where it is held by the forceps, is felt or seen to give way (irido-dialysis) (Fig. 115). The iris is then drawn a little further out from the wound, and one side of the dialysis is divided with the scissors as near the scleral wound as possible. The iris held in the forceps is then pulled over to the other angle of the wound, and as much of it as possible is pulled out and divided close to the scleral incision (Fig. 116). The angles of the incision are freed from iris by means of the spatula and the conjunctival flap is replaced in position. Both eyes are then bandaged.

=After-treatment.= The patient should be kept in bed for a week, and during the first four days should not be allowed to raise the head from the pillow. After that time the eye not operated upon may be uncovered; eserine should have been instilled into it before the operation and at subsequent dressings to prevent the possible onset of glaucoma owing to the dilatation of the pupil which follows the application of the bandage to the eye. It is not necessary to use any mydriatic or myotic for the eye which has been operated upon.