[Ill.u.s.tration: FIG. 114. IRIDECTOMY FOR GLAUCOMA. Showing the position in which the iris should be grasped with forceps.]

[Ill.u.s.tration: FIG. 115. IRIDECTOMY FOR GLAUCOMA. Showing the irido-dialysis produced before division.]

=Complications.= These may be immediate or remote.

=Immediate.= 1. In pa.s.sing a Graefe's knife into the anterior chamber to make the section, care must be taken that the cutting edge is directed upwards. If by accident it should be inserted with the cutting edge directed downwards the knife should be withdrawn and the operation postponed for a day or two until the anterior chamber has re-formed.

Care must be taken that the cutting edge is kept on the same plane as the upper edge of the back of the knife, otherwise the incision is liable to pa.s.s further back than is intended.

2. _Splitting the cornea._ The anterior chamber often being little more than a potential s.p.a.ce, the knife may be pa.s.sed between the lamellae of the cornea and may not enter the anterior chamber at all. The indication that the knife-point is not in the anterior chamber is that there is no diminished resistance, such as is usually felt when the knife enters the chamber; if its point be slightly depressed, the cornea will be seen to dimple in over the position of it, showing that the point is not free in the anterior chamber.

3. _Locking of the knife._ This is due to the fact that the puncture and counter-puncture are not made in the same plane, the knife being twisted. It is much more liable to occur if a knife be chosen with a blade which is not sufficiently stiff. As a rule the blade can be made to cut out, but failing this, the knife should be withdrawn sufficiently to allow a fresh counter-puncture to be made, or else withdrawn altogether and the operation postponed.

[Ill.u.s.tration: FIG. 116. IRIDECTOMY FOR GLAUCOMA. Division of the iris to form the inner angle of the coloboma. The iris is pulled out as far as possible before removal.]

4. _Wound of the lens._ The great safeguard against wounding the lens is to keep the point of the knife always superficial to the iris and in the periphery of the anterior chamber. If the lens be definitely wounded at the time of the operation it should be extracted immediately after the iridectomy. If the wound be only subsequently discovered (usually about the third or fourth day), provided the lens be not presenting in the wound, the eye should be allowed to settle down and the traumatic cataract extracted some time after the tenth day.

5. _Presentation of the lens in its capsule._ The lens may present in its capsule at the time of the operation or be found subsequently on the dressings. In the latter instance it is very liable to carry iris into the wound, and a cystoid cicatrix results. This accident is usually due to increased tension in the vitreous chamber; a large incision, especially if placed rather far back in the sclerotic, will also favour its occurrence. If the accident should happen to one eye, and acute glaucoma be present in the other, it is advisable to do a posterior scleral puncture before the iridectomy is performed. Partial dislocation of the lens forward may occur after the wound has healed, leaving the tension of the eye not reduced. This is a condition extremely difficult to recognize, and it is usually only discovered pathologically; if recognized clinically, extraction of the lens should be performed (Fig.

117).

6. _Intra-ocular haemorrhage. Haemorrhage into the anterior chamber_ occurs at the time of the operation and is readily absorbed; occasionally it may persist for a considerable time in cases of glaucoma of long standing.

After the operation haemorrhage may also occur from the cut margin of the iris, which never heals, viz. never becomes covered with endothelium.

The haemorrhage may occur as late as two weeks after the operation and may recur from time to time; it is especially liable to occur in old people with arterio-sclerosis. It is usually absorbed without giving rise to any trouble beyond delay in the convalescence.

_Retinal haemorrhages_ are frequent and usually small, but a considerable haemorrhage may take place into the vitreous. As a rule these clear up satisfactorily unless the macular region be involved.

[Ill.u.s.tration: FIG. 117. GLAUCOMA IRIDECTOMY. Failure to relieve the tension owing to displacement of the lens.]

_Subchoroidal haemorrhage._ Of all the immediate complications which follow an intra-ocular operation this is by far the worst. The haemorrhage is due to the giving way of a large choroidal vessel following the sudden reduction of tension, with the result that the choroid and retina are stripped up from the sclerotic, and, with the lens, may be partially extruded from the wound in the globe, from which the haemorrhage then proceeds. It may occur whilst the patient is still on the operating table, or it may be discovered only after he has been put back to bed, the blood being seen coming through the dressings.

Patients who have this condition complain of pain in the 'corner of the eye' at the time of the operation. The treatment consists in evisceration or enucleation. It is probable that limited extravasation of blood may also occur, which need not end in disintegration of the eye, but may cause vitreous opacity and defective vision for some weeks after the operation.

=Remote.= 1. _The tension is not reduced by the iridectomy._ In acute cases the prognosis with regard to the reduction of the tension and the improvement of vision is very satisfactory. The same cannot be said of chronic cases, especially those which have been operated on rather late in the disease. If iridectomy, which may be repeated downwards or extended from the previous coloboma, fail to reduce the tension, one or more of the following measures should be adopted:--

(_a_) The use of eserine.

(_b_) Sclerotomy.

(_c_) Cyclo-dialysis.

(_d_) Sclerectomy.

(_e_) Post-scleral puncture.

It is probably in this order that they should be tried.

2. _Prolapse of the iris and irido-cyc.l.i.tis_ should be treated as already indicated under cataract extraction (see p. 208).

3. _The onset of glaucoma in the other eye_ may be induced by the dilatation of the pupil caused by bandaging, and is best avoided by the use of eserine. If it should occur, an iridectomy should be performed.

4. _Astigmatism_ produced by the incision is corrected with gla.s.ses.

This astigmatism is very marked, often amounting to six or eight diopters or more.

IRIDECTOMY FOR SMALL GROWTHS OF THE IRIS

=Indications.= This is performed--

(i) As a diagnostic measure.

(ii) As a curative measure.

In the latter instance it is obvious that the growth must be very small and situated at the free margin of the iris to yield a satisfactory result, especially if it be of a malignant character.

=Operation.= The operation is performed under cocaine, eserine having been previously instilled in order to contract the pupil.

_First step._ An incision should be made with a narrow Graefe's knife in the limbus in a position most suitable for removing the growth. The incision should be as large as possible so as to avoid wiping off any portions of the growth into the anterior chamber.

_Second step._ The iris should be seized well in the periphery so as to avoid breaking up the growth; it is then withdrawn with the growth, and the latter removed.

IRIDECTOMY FOR PROLAPSE OF THE IRIS

This operation is usually performed for prolapse of the iris following a wound of the cornea or limbus, and may be attempted up to about the third day after the original injury.

=Operation.= A general anaesthetic is usually desirable. The prolapsed iris should be seized with the forceps and withdrawn from the wound. A second pair of forceps is used to take a fresh hold on the iris, which can usually be drawn out further (Fig. 118). It is then divided as close to the corneal wound as possible. The iris usually flies back into the anterior chamber clear of the corneal wound by its own elasticity, but if it does not do so it should be freed with a spatula. The pupil should be kept subsequently under atropine.

TRANSFIXION OF THE IRIS

=Indications.= This operation is undertaken in cases of iris bombe when iritis is still present and when an iridectomy would subsequently lead to a drawn-up pupil. It is also of service to evacuate the contents of cysts of the iris (local iris bombe).

[Ill.u.s.tration: FIG. 118. PROLAPSE OF THE IRIS THROUGH A PUNCTURED WOUND OF THE CORNEA. Method of withdrawing the iris by two pairs of iris forceps before removal.]

=Instruments.= Speculum, fixation forceps, Graefe's knife (narrow).

=Operation.= The knife is entered at the limbus from the outer side directly opposite the occluded pupil. The apex of the iris bombe is transfixed and the point of the knife made to appear above the pupillary area; the iris bombe on the other side of the pupil is then transfixed and the knife is withdrawn.

THE DIVISION OF ANTERIOR SYNECHIae

=Indications.= Anterior synechiae rarely require division unless they are likely to cause tension or the adherent iris is considered a source of danger to the eye on account of its liability to septic infection. If the synechiae are causing tension, the method of division described under sclerotomy is probably the most satisfactory; otherwise the following method devised by Lang can be used.

=Instruments.= Speculum, fixation forceps, Lang's knives--one with a sharp point, and one blunt.

=Operation.= Under cocaine. The incision is made at the limbus in a favourable situation for the division of the synechia. The sharp-pointed knife is introduced into the anterior chamber and then rapidly withdrawn so as not to lose the aqueous. The blunt knife is then inserted through the incision and, partly by cutting and partly by tearing, the synechia is divided in a direction from the periphery towards the pupil.

The operation is not at all easy to perform, since the iris gives before the knife. Great care should be taken to avoid evacuating the aqueous, as the operation is thereby rendered much more difficult or even impossible.