Fig. 98. Opening the Capsule with Forceps in Cataract Extraction. The forceps are inserted closed, brought in contact with the lens, opened, and the capsule grasped between the blades and withdrawn by a gentle side-to-side movement.
Third step. The capsule of the lens is opened. This is done in order to allow the lens nucleus and soft matter to escape. Since the anterior capsule becomes opaque after the removal of the lens, owing to the multiplication of the cells in their attempt to lay down new lens fibres, it is desirable to remove a portion of the anterior capsule from the pupillary area. This may be performed (a) by means of capsule forceps which are inserted closed, and when in position over the lens are opened as widely as possible without entangling the iris, then pressed down on to the anterior capsule of the lens and closed; in this manner the portion of the capsule thus included is removed by a slight lateral movement (Fig. 98); (b) by means of a cystotome, the lens capsule being opened by a triangular or T-shaped incision over the pupillary area; (c) by the point of the knife as it passes across the anterior chamber; (d) by a discission needle before the section is made. When the capsule of the lens has been opened properly the lens nucleus is usually seen to come forward. The advantage of the capsule forceps over the other methods is that they remove a larger portion of the capsule and leave no tags which may become incarcerated in the wound. On the other hand they are somewhat more difficult to use; more pressure on the lens is required, and therefore dislocation of the lens in its capsule may result. It is, therefore, not advisable to use them in cases in which a fluid vitreous is suspected. If the teeth of the forceps are not well made they will not grasp the capsule; it is therefore always advisable to have the cystotome in readiness. The cystotome also should be used when the anterior chamber becomes filled with blood so that the margin of the iris cannot be seen and there is a risk of the iris being grasped by the forceps.
The method of opening the capsule with the point of the knife or needle is useful in cases of extraction without iridectomy; the pupil should be dilated before the operation.
Fourth step. Delivery of the lens is performed by a gentle pressure, combined with massage, on the extreme lower margin of the cornea with a curette or spoon, until the upper margin of the lens presents in the wound, when the pressure is gradually made upwards over the cornea until the lens is delivered. Delivery of the lens may be prevented by—
(a) Imperfect opening of the capsule, which is usually the result of using a blunt cystotome; if capsule forceps are used this difficulty hardly ever arises.
(b) Too small an incision. The margin of the nucleus may present and not be able to pass the wound. The wound must then be enlarged with the iris scissors and the lens delivered in the ordinary way. Only by experience can the amount of pressure required for the delivery of the lens be gauged.
(c) A sticky consistency of the cortex is not infrequently found in cases of immature cataract. When the lens presents and cannot be delivered readily it may be helped out by means of the cystotome plunged into its substance, pressure being used on the cornea at the same time.
Fig. 99. Cataract Extraction. Replacing the iris, and any tags of capsule which may be in the wound, with an iris spatula.