b. Laceration of the Capsule of the Lens.—This is performed by insinuating a sharp curved needle under the corneal flap, avoiding the iris, and then tearing up the anterior capsule through the dilated pupil, the chief point to be attended to being that the capsule be lacerated in its entire length.
c. Removal of the Lens.—This must be done with the most extreme caution and gentleness, lest the vitreous humour be also evacuated. The surgeon's object is to tilt the lens so as to turn it slightly on its transverse axis, and cause the edge nearest the section to rise out of the capsule and appear at the wound. This is best done by gentle pressure at the required spot by the back of the needle, or by a common probe. When the lens begins to protrude the pressure must be very, gentle, lest it be forced out suddenly and the vitreous follow it.
Soft portions of the lens are apt to remain adherent to the wound in the cornea. These must be removed by scoop or probe.
Varieties in the method of Flap Extraction.—Jacobsen of Königsberg in every case gives chloroform. He always makes his flap in the boundary line of the cornea and the sclerotic, through a vascular structure, and he believes that union is on this account more rapid, and after extraction removes that portion of the iris which appears to have been most exposed to bruising during the exit of the lens.
The operation of extraction may in many cases be either preceded or followed by iridectomy, as proposed by Mooren, Von Graefe, and others. The following operation seems to diminish the risks to a very great extent:—
Professor Von Graefe's Operation.—The lids are separated by a speculum, and the eyeball is drawn down by forceps placed immediately below the cornea. The point of a small knife, of which the edge is directed upwards, is inserted at a point fully half a line from the margin of the cornea near its upper part, so as to enter the anterior chamber as peripherally as possible. The point should not be directed at first towards the spot for counterpuncture; nor till the knife has advanced fully three and a half lines within the visible portion of the anterior chamber, should the handle be lowered and the point directed so as to make a symmetrical counterpuncture, which will give the external wound a length of four and a half or five lines. As soon as the resistance to the point is felt to be overcome, showing that the counterpuncture is effected, the knife must at once be turned forward, so that its back is directed almost to the centre of the ideal sphere of the cornea, whether the conjunctiva is transfixed or not, and the scleral border is divided by boldly pushing the knife onwards and again drawing it backwards. This portion of the operation is concluded by the formation of a conjunctival flap a line and a half or two lines in length. A section thus made is almost perpendicular to the cornea, a circumstance much facilitating the passage of the lens, and the line of incision is nearly straight, so that the wound does not gape. The iris should be excised to the very end of the wound, and the capsule most freely opened by a V-shaped laceration. Any lens, even the hardest, may then be removed without the introduction of an instrument into the eye, but Von Graefe's experience shows it to be advisable to assist the evacuation by the hook in about one case in eight. In a certain number of cases the lens will escape without difficulty when the operator presses on the posterior lip of the wound, especially when the back of the spoon is made to glide along the sclera; should this not occur, Von Graefe uses a peculiar blunt hook, or occasionally, though rarely, a spoon. A compressing bandage is applied, and replaced at intervals.[88]
We are recommended to perform it in two sets of cases:—
1. Those in which the eye is known to be unhealthy and liable to inflammations, specially of iris, retina, or choroid. In cases where the patient has already lost an eye, Von Graefe thinks iridectomy should always precede extraction. In the above, then, it is a precautionary measure, and, if convenient, should be performed three, four, or even six weeks before the extraction.
2. It is recommended to be performed at the same time as extraction in all cases in which the operation has presented any special difficulties, or has not gone smoothly, e.g. in cases where the lens has required much force to expel it, either from the flap of cornea being too small, or from adhesions between the lens and capsule; or, again, in cases in which there is a tendency to prolapse of the iris, in which any of the cortical substance has been necessarily left behind, or in which old adhesions had existed between the iris and capsule, or between the cornea and iris.
Operations for Artificial Pupil.—The cases are by no means unfrequent in which it is necessary to remove or destroy a portion of the iris to admit light to the retina. In cases of excessive prolapse of the iris after extraction of the lens, where the iris has formed adhesions to the wound, and still more frequently in cases where central opacities of the cornea have fairly occluded the natural pupil, the only chance for vision is to enlarge the old one, or make a new pupil by removal of the iris.