A System of Operative Surgery Part 33

8. _Defective vision._ Gla.s.ses have to be worn after removal of the lens. Usually patients who were previously emmetropic require about + 11 to see clearly for distance and + 15 for near vision.

The section produces some flattening of the corneal curvature at right angles to the line of the incision; this usually amounts to about two diopters.

COUCHING

Couching is the removal of the lens from the pupillary area by depressing it backwards into the vitreous. It is rather a relic of the past than a present-day operation, although it is extensively practised by quacks in India. Under certain circ.u.mstances the operation still seems justifiable; it is very simple, and is followed by immediate restoration of vision, but the subsequent risks of irido-cyc.l.i.tis, retinal detachment, and glaucoma are so great, that, according to some authorities, couching should only be undertaken in preference to extraction when the latter operation has only a chance of one in three of giving satisfactory vision.

=Indications.= The chief indications for its performance are:--

(i) The presence of a fluid vitreous, the patient having had the lens of the other eye extracted with bad results.

(ii) In the insane, where it would be impossible to carry out the after-treatment of extraction satisfactorily.

=Operation.= The operation is usually done under cocaine; in the case of the insane a general anaesthetic is usually necessary. It has been performed by simple depression of the lens backwards into the vitreous with a needle pa.s.sed through the cornea (anterior route). This operation yields unsatisfactory results owing to the lens being liable to return into the pupil; this can be partly overcome by sweeping the needle round the periphery of the lens so as to divide the suspensory ligament, but the operation is not so satisfactory as when the needle is pa.s.sed in from behind the ciliary body and the lens pressed down from behind (posterior route), to which the following description applies. The capsule of the lens should be torn freely, so that some absorption may subsequently take place and diminish the risk of complications.

=Instruments.= Speculum, fixation forceps, needle.

_First step._ The pupil should be dilated with atropine. The patient's head should be well raised on the table. The needle is pa.s.sed through the sclerotic about 5 millimetres behind the limbus to the outer side.

The posterior capsule of the lens is then freely divided by a sweeping movement.

_Second step._ The needle is next made to appear in the lower part of the pupil by carrying it round the lower and outer border of the lens.

The anterior capsule is then freely divided.

_Third step._ The shaft of the needle is laid flat on the surface of the lens towards its upper part, and by raising the handle of the needle the lens is displaced backwards into the vitreous. The tearing of the suspensory ligament on the inner side may be a.s.sisted by the cutting edge of the needle during depression.

=Complications.= _Immediate._ Difficulty may be experienced in making the lens lie at the bottom of the vitreous, and it is only by frequent depression of the lens backwards and downwards, with a sweeping movement of the needle to divide the suspensory ligament, that the desired effect can be obtained.

_Remote._ The lens nucleus may prolapse through the pupil into the anterior chamber. If this should happen, the patient should be placed on his back and the pupil dilated with atropine; if the nucleus does not go back into the vitreous chamber it should be depressed by means of a needle pa.s.sed through the cornea.

Glaucoma may result from the dislocation of the nucleus into the anterior chamber and should be treated as described above. It may also be present with a lens which is dislocated backwards. This condition is very liable to end in loss of sight. Probably the only hope of relieving the tension is by the use of eserine or the performance of a cyclo-dialysis.

Cyc.l.i.tis and retinal detachment may also follow, and usually end in blindness.

CHAPTER III

OPERATIONS UPON THE IRIS

IRIDOTOMY

=Indications.= Iridotomy is an operation which is performed when the iris has become drawn up after a cataract extraction, so that there is no pupil, or the pupillary area is covered by the upper lid. A long interval should elapse between the extraction and the iridotomy, since these cases have usually suffered from cyc.l.i.tis following the operation.

Iridotomy should not be performed for at least six months after all signs of cyc.l.i.tis have disappeared, for the frequent failure of the operation is due to the fact that the opening made in the iris and underlying capsule becomes filled with fibrous exudation as the result of cyc.l.i.tis, which is frequently set up again by the operation if undertaken before a sufficient time has elapsed for the eye to settle down after the inflammation. The ideal operation, therefore, is to make an artificial pupil with the least amount of trauma to the ciliary body.

=Instruments.= Speculum; fixation forceps; a long, narrow, bent 'broad needle'; Tyrrell's hook, iris scissors, iris forceps, and spatula.

=Operation.= Many operations have been devised for this most troublesome condition, but the following is the one that the author has found to be successful.

The operation is usually performed under a general anaesthetic, but this is not essential.

_First step._ The surgeon stands facing the patient on the same side as the eye to be operated on. The long, bent, broad cutting needle is pa.s.sed into the anterior chamber from the limbus downwards and inwards, and is driven directly through the iris and underlying capsule. The needle is then made to pa.s.s in an upward and outward direction behind the iris into the pupillary area above, or if no pupil be present, again through the iris (Fig. 102). The bent broad needle is made to cut laterally by slightly deflecting the handle so as to produce a band of iris and capsule; the cutting needle is then withdrawn.

_Second step._ A Tyrrell's hook, bent to the correct angle, is pa.s.sed beneath the band (Fig. 103), which is drawn into the wound and removed with iris scissors. A large opening is thus obtained with a minimum amount of trauma. If the hook should slip, the band may be seized with iris forceps, withdrawn from the wound, and removed.

=Alternative methods.= The following methods have been practised:--

=Simple incision= across the fibres of the iris by means of Graefe's or Knapp's knife.

=Division with scissors= through a wound of the limbus.

By these two methods the opening produced is small, and is very liable to be closed by the subsequent cyc.l.i.tis. The following operation yields more satisfactory results.

[Ill.u.s.tration: FIG. 102. IRIDOTOMY. Showing the incision with a long, bent broad needle.]

[Ill.u.s.tration: FIG. 103. IRIDOTOMY. Showing the method of withdrawing the band of iris and capsule with a Tyrrell's hook.]

=Kuhnt's operation.=

=Instruments.= Speculum, fixation forceps, Graefe's knife, iris forceps and scissors.

_First step._ The surgeon, standing facing the patient, enters the anterior chamber about 2 millimetres inwards from the limbus at the junction of the middle and lower third of the cornea with a Graefe's knife, the cutting edge directed downwards. The knife is then made to penetrate the iris and underlying capsule, and to travel beneath this to a similar point on the other side, where it is made to come back again into the anterior chamber by again penetrating the iris, and finally out again through the cornea. The knife is then made to cut out in a downward direction.

_Second step._ Iris forceps are inserted and the flap of iris and capsule is withdrawn and as much of it removed as possible. A more or less triangular opening usually results.

=Ziegler's operation.=

=Instruments.= Ziegler's knife needle, speculum, fixation forceps.

The object of the operation is to cut a V-shaped flap in the iris and underlying capsule, folding the flap backwards on its base so as to form a triangular opening in the iris membrane to serve as a pupil.

_First step._ The knife needle is entered at the corneo-sclerotic junction with the blade turned on the flat and is pa.s.sed completely across the anterior chamber to within 3 mm. of the apparent iris periphery. The knife is then turned edge downwards, and carried 3 mm. to the left of the vertical plane (Fig. 104).

[Ill.u.s.tration: FIG. 104. IRIDOTOMY BY ZIEGLER'S METHOD. Showing the shape of the knife and the position of the first puncture in the iris; the cutting is performed by a sawing movement.]

_Second step._ The point is now allowed to rest on the iris membrane, and with a dart-like thrust the membrane is pierced. Then the knife is drawn gently up and down with a saw-like motion, without making much pressure on the tissue to be cut, until the incision has been carried through the iris tissue from the puncture in the membrane to just beneath the corneal puncture. This movement is made wholly in a line with the long axis of the knife, the shank pa.s.sing to and fro through the corneal puncture, loss of the aqueous being avoided in the manipulation (Fig. 105).

_Third step._ The pressure of the vitreous will now cause the edges of the incision to bulge open immediately into a long oval. The knife-blade is raised until it is above the iris membrane, and is then swung across the anterior chamber to a corresponding point on the right of the vertical plane. Owing to the disturbance in the relation of the parts made by the first cut, this point is somewhat displaced and the second puncture must be made 1 mm. further over.

_Fourth step._ With the knife-point again resting on the membrane, a second puncture is made and the incision is carried rapidly forward by the sawing movement to meet the extremity of the first incision at the apex of the triangle, thus making a V-shaped cut. Care must be taken that the pressure of the knife-edge on the tissue shall be most gentle, and that the second incision shall terminate a trifle inside the extremity of the first, in order that the last fibres may be severed and thus allow the apex of the flap to fall down behind the lower part of the iris membrane (Fig. 106). When the operation has been completed the knife is turned on the flat and withdrawn.

IRIDECTOMY

The operation of iridectomy differs widely in its performance, according to the different conditions for which it is used. Hence it is better to prefix the condition for which it is employed, thus: preliminary iridectomy, optical iridectomy, glaucoma iridectomy.