Part 31 (1/2)

CAPSULOTOMY

Capsulotomy is the division of the opaque capsular membrane left after a cataract has been removed.

=Indications.= After a cataract has been removed, either by discission or extraction, an opaque membrane is usually left. This is due to the proliferation of the cells in the anterior capsule of the lens while attempting to lay down new lens fibres. Although the posterior capsule is clear and free from cells, those from the anterior capsule may spread to it and so render it opaque. A fibrinous exudate may also organize and help to thicken the membrane (Fig. 87). For these reasons and also because the soft matter may not have absorbed entirely, it is not advisable to operate too soon after a cataract has been removed. There should be at least six weeks' interval after an extraction has been performed. A few surgeons operate earlier than this, the idea being that the membrane is then softer and more easily divided.

[Ill.u.s.tration: FIG. 87. SECONDARY CATARACT. Opaque capsule after cataract extraction.]

Although the operation of discission for after-cataract (capsulotomy) is simple it is not to be undertaken lightly. The patient's vision should be less than 6/18. In former days the operation was looked upon as attended with as much risk as the extraction, owing to the frequency with which it was followed by inflammation. The reasons for this seem to have been want of proper antiseptic precautions, the pa.s.sage of the needle through the non-vascular corneal tissue instead of through the conjunctiva, and also the use of a badly made needle, often resulting in prolapse of the vitreous into the wound. A proper discission needle should have sufficient width in its spear-like point to cut a hole large enough to admit the shaft freely; hence needles which have been sharpened several times should be discarded. It need hardly be said that there should be no signs of cyc.l.i.tis (kerat.i.tis punctata) present when the operation is undertaken.

=Instruments.= These are the same as for discission, with the addition of a needle with a long cutting edge.

[Ill.u.s.tration: FIG. 88. CAPSULOTOMY. _The method of incising the capsule._ The fulcrum of movement of the needle is where the shaft lies in the sclerotic.]

[Ill.u.s.tration: FIG. 89. CAPSULOTOMY. _The method of dividing a dense band._ This is done with two needles.]

=Operation.= Capsulotomy is best performed by artificial light under cocaine. The cutting needle is inserted into the anterior chamber as in the previous operation. The point is then thrust through the membrane below (but it should not penetrate deeply, otherwise the vitreous will be torn) and an incision is made in an upward direction. This incision usually gapes sufficiently to give a clear pupil (Fig. 88). Those surgeons who operate early try to cut out a triangular portion of the membrane. When a dense band is present which gives before the needle and cannot be divided, a second or ordinary discission needle should be pa.s.sed into the anterior chamber from the limbus opposite to the cutting needle. The discission needle is made to pa.s.s behind the band whilst the cutting needle lies in front of it. By a rotary movement of the discission needle around the cutting needle the band is carried against the edge of the latter and so divided. The needles are then withdrawn (Fig. 89).

=Results.= These are good as a rule, but the operation may have to be performed again owing to an insufficient or non-central opening being obtained in the membrane, or to a fresh membrane forming; this is liable to take place if any irido-cyc.l.i.tis follow the operation.

=After-treatment.= This should be carried out as described for needling.

EVACUATION

=Indications.= (i) In cases of increased tension a.s.sociated with soft lens substance in the anterior chamber.

(ii) To accelerate the absorption of soft lens matter from the anterior chamber. As a rule it is only undertaken for the former condition.

=Instruments.= Speculum, fixation forceps, bent broad needle, curette.

=Operation.= Under cocaine.

_First step._ An incision is made behind the limbus, usually in an upper segment of the cornea, by means of a bent broad needle. The point of the instrument is pa.s.sed into the anterior chamber immediately behind the limbus with the handle at right angles to the cornea; directly the anterior chamber has been entered the handle is depressed so that the point of the instrument shall turn forwards and avoid injuring the iris.

The blade is pa.s.sed on into the anterior chamber until the point reaches about the centre of the pupil. It is then either withdrawn directly, or, if a larger incision be desired, lateral pressure is made so that in withdrawing the blade the wound is enlarged.

_Second step. Evacuation._ With the rush of aqueous which follows the incision some soft matter is usually evacuated; then a curette may be introduced, if necessary, and the lens fragments removed by gentle manipulation. Occasionally the iris may prolapse into the wound; if this happens it should be replaced, but if it occur more than once the prolapsed portion should be removed. Suction apparatus has been used for removing the soft lens matter, but it is not to be recommended in most cases, owing to the difficulty of sterilization and the trauma which it may cause. After-treatment as for needling should be carried out.

EVULSION OF THE CAPSULE

=Indications.= (i) In congenital cataract when the lens consists of little more than a dense capsular ma.s.s.

(ii) In dense capsular membranes following removal of a lens by discission in which a cutting needle cannot make a hole.

=Instruments.= Speculum, fixation forceps, keratome, capsule forceps, discission needle.

=Operation.= A general anaesthetic is usually desirable.

_First step._ The pupil is previously dilated with atropine. In the case of congenital cataract a discission needle is first pa.s.sed into the ma.s.s to estimate its consistency. If it consist of little more than capsule an incision is made at the limbus with the keratome as described for evacuation.

_Second step._ The blades of the capsule forceps are then inserted closed, opened, and the opaque capsule grasped and withdrawn from the eye. The speculum is then removed and a pad and bandage applied. The pupil should be kept dilated with atropine subsequently, as a certain amount of irido-cyc.l.i.tis following the operation is not infrequent.

Occasionally the iris may become entangled in the wound, and it should then be removed.