Iridesis.—Critchett's Operation of Ligature.[89]—Patient being put under chloroform, the ball is fixed by the wire speculum, and also by a fold of conjunctiva being seized by forceps. An opening is then made with a broad needle through the margin of the cornea, close to the sclerotic, just large enough to admit the canula forceps, with which a small portion of iris close to its ciliary attachment is seized and drawn out; a piece of fine floss silk, previously tied in a small loop round the canula forceps, is slipped down and carefully tightened round the prolapsed portion. This speedily shrinks, and the loop may generally be removed about the second day. The chief advantage claimed for this method is the ease with which the size of the new pupil can be regulated. It is also suitable in cases of conical cornea, where it is wished to change the form of the pupil into a narrow slit.
N.B.—The ends of the ligature must be left sufficiently long to avoid any risk of their being drawn out of sight into the substance of the cornea, or even into the ball, by retraction of the fibres of the iris.
Corelysis.—Freeing of the Pupil.—An operative procedure for separating posterior adhesions of the iris to the lens. In it the surgeon hopes to act, not on the iris, as in the operations for artificial pupil, but only on the bands of false membrane which distort the pupil.
The operation is briefly as follows:—The eye being firmly held by a wire speculum, and forceps pinching up the conjunctiva, a broad needle is passed rapidly through the cornea at a point which may give easy access to the adhesion to be torn through. This point is generally at the opposite margin of the irregular pupil, so that the needle may pass through the cornea in front of the one side of the iris, then through the orifice of the pupil, so as to reach the back of the other side. The needle is withdrawn gradually, so as to lose as little of the aqueous humour as possible, and then the spatula hook, called after the inventor of the operation, Mr. Streatfeild, is introduced. It is used first as a spatula, that is, with its blunt, though polished edge, to separate the adhesions, and if this is unsuccessful, as a hook (Fig. xiv.), so as to catch and tear them. In cases which resist the instrument used in both of these ways, Mr. Streatfeild has used very fine canula-scissors to cut the adhesions.[90] Such a further complication of the operation practically alters its character into an operation for artificial pupil, q.v.
Fig. xiv. [91]
Iridectomy.—In cases of acute glaucoma, irido-choroiditis, and all deep inflammations of the eye in which the ocular tension is increased, also in certain cases of flap extraction already alluded to, the operation of iridectomy as originally proposed by Von Graefe will be found of use.
Operation.—The patient recumbent, and the eye absolutely fixed by speculum and forceps, a linear incision, varying in length from one-sixth to one-fourth of an inch, is made just at the margin of the cornea. The point of election is the upper pole of the cornea. The lens must not be wounded. The best instrument for making the section is an ordinary linear extraction knife, bent at an angle to admit of its being introduced from above. The iris will protrude through the wound, or, if adherent, must be drawn out by forceps, and then is to be cut off with scissors. The operation is rarely successful, unless a third, or at least a fourth, of the iris be removed.
Excision of a Staphylomatous Cornea.—There are certain cases in which the whole or greater part of the cornea bulges forward in a great blue projecting tumour. It is very ugly as it protrudes between the lids and prevents their closure; besides this, from its exposure it frequently inflames, even ulcerates, and has a most injurious effect on the other eye. In the cases suitable for operation vision is completely gone, without hope of its restoration by any operative procedure.
The best thing for the patient is to have just enough of the staphyloma removed to enable the remains of the eyeball to form a good stump for an artificial eye. Various means have been suggested for doing this, varying in extent and severity from a mere shaving off the apex of the staphyloma to excision of the whole eyeball.