(1.) By linear, or perhaps, more correctly, rectilinear incision. This method is specially suited for cases of soft cataract.
Operation.—A fine spear-shaped needle is very cautiously introduced through the cornea, about a line from its outer margin, and the anterior capsule lacerated, and the lens broken up, great care being taken not to injure the posterior capsule. The pupil must then be kept freely dilated, the wound heals at once, and the aqueous humour reaccumulates.
Fig. xii.
Fig. xiii.
From three to six days after this first operation, a linear incision (Fig. xii.) is made in the outer side of the cornea by a straight stab from a double-edged knife, or rather spear. The size of the incision must vary with the size and consistence of the lens, and can be regulated by the breadth of the knife and the distance to which it is entered. By careful withdrawal of the knife, in many cases a large portion of the soft lens can be removed along with it, and then what remains must be cautiously lifted out by a flat spoon introduced through the wound, and behind the remains of the lens.
Care must be taken lest any of the lens substance remain in the wound; with this precaution the incision generally heals rapidly, and with much less risk of general inflammation of the ball than in the ordinary flap operation of extraction.
Extraction of Soft Cataract by Suction.—Mr. T. P. Teale, of Leeds,[87] has invented an instrument by which the removal of soft cataract is made more easy, through a linear incision by suction, applied through the medium of a hollow curette furnished with an india-rubber tube and mouth-piece.
The curette is of the usual size, but is roofed in (instead of being merely grooved) to within one line of its extremity, thus forming a tube flattened above, but terminating in a small cup. This is screwed into an ordinary straight handle, which is hollow for a short distance, far enough to join with a second tube fixed at right angles to the handle, and into which the india-rubber pipe and mouth-piece, through which suction is to be made, is attached. In many cases it seems to serve its purpose extremely well.