Part 32 (1/2)
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 ma.s.sage, 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 pa.s.s 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.
[Ill.u.s.tration: 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forceps are inserted closed, brought in contact with the lens, opened, and the capsule grasped between the blades and withdrawn by a gentle side-to-side movement.]
(_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.
If from these or any other causes the suspensory ligament rupture and the vitreous present in the wound, the lens should be removed with the vectis. The vectis, which should be made of stiff steel, is pa.s.sed vertically into the incision and behind the lens nucleus by depressing the handle; with a steady gentle pressure forwards it is then withdrawn together with the nucleus. The forward pressure should be such as to prevent the instrument slipping on the nucleus, for if it does so the accident is nearly always followed by a rush of vitreous. A Pagenstecher's spoon may be used instead of the vectis, and is to be preferred in cases where a small nucleus is suspected, since the latter may slip through the loop of the vectis and fail to be delivered.
=Fifth step.= _Toilet of the wound._ After the nucleus has been extracted, all the soft matter should be removed as far as possible by gentle expression with the spoon. The angles of the coloboma in the iris should be replaced by stroking it inwards on its anterior surface with the iris spatula, paying particular attention to the angles of the wound (Fig. 99). The spatula should also be pa.s.sed throughout the extent of the wound so as to free it from any capsule which may have prolapsed into it. The conjunctival flap is then placed in position by stroking it upwards with the iris spatula.
[Ill.u.s.tration: FIG. 99. CATARACT EXTRACTION. Replacing the iris, and any tags of capsule which may be in the wound, with an iris spatula.]
=After-treatment.= Atropine is instilled either at the time of operation or at the first dressing, and continued until all signs of redness of the eye have disappeared. The patient should remain in bed for at least ten days, both eyes being bandaged during the first four days. The eye that has been operated on should be covered for at least two weeks; subsequently a shade or dark gla.s.ses should be worn.
=Modifications.= The operation may be modified in various ways.
=The incision.= _The position_ of the incision has undergone many modifications. The one described above is now in general use.
_The size_ of the incision should be increased when (_a_) a large nucleus is expected, as in old people; (_b_) an immature cataract is to be extracted; or (_c_) a fluid vitreous is suspected, so that the lens may be delivered with as little pressure as possible.
=The iridectomy= may be omitted. _Extraction without iridectomy_ is undoubtedly the ideal operation; it leaves the pupil unbroken and the eye looking normal to external appearance. Further, the pupil reacts more strongly to light than if an iridectomy has been performed. The presence of the iris further prevents the prolapse of any capsule into the wound. At the same time it is attended with considerable risk of prolapse, which, as has been pointed out, is a very great danger to the eye. With proper care this probably only occurs in about 5% of the patients operated upon, but is so serious that the opinion of most surgeons is in favour of the combined method (iridectomy and extraction); but at the same time it is the practice of many surgeons to omit the iridectomy under the following circ.u.mstances: first, if the patient be young and the deformity will interfere with his getting employment; secondly, if extraction of the lens in its capsule be performed the unbroken circle of the iris will help to prevent the prolapse of the vitreous which is otherwise so liable to take place.
[Ill.u.s.tration: FIG. 100. MCKEOWN'S IRRIGATION APPARATUS FOR WAs.h.i.+NG OUT THE ANTERIOR CHAMBER. The second and third terminals are the most useful.]
Eserine (gr. ii ad ?i) should be used to prevent prolapse of the iris after the extraction has been performed, and should be continued once a day until a good anterior chamber is present, which is usually in about twelve to twenty-four hours, when atropine should be subst.i.tuted. If the iris betray any liability to prolapse after the operation, as shown by the drawing upwards of the pupil, an iridectomy should be performed before the patient leaves the table. In any case the eye should be examined on the evening of the operation, and, if prolapse has occurred, that portion of the iris should be removed. If a prolapse of the iris occurs and is not discovered until the wound has healed, the conjunctiva should be dissected off the surface in the form of a flap and the iris tissue drawn out of the wound and removed, the angles caught in the scar being freed if possible. The opening in the globe is subsequently closed by replacing the conjunctival flap in position, or, if it has not been possible to preserve the conjunctiva over the cicatrix, by raising a flap from the ocular conjunctiva in the neighbourhood and st.i.tching it down over the opening in the globe. Not infrequently this operation is followed by an attack of acute iritis, which usually subsides under treatment.
_Preliminary iridectomy._ The iridectomy may be performed at a previous operation. It has the advantages that the surgeon learns how the patient will behave under operation, and how the eye will react to such an operation. There is an absence of bleeding at the second operation, which makes it easier, and there is less liability for the iris to become adherent to the capsule. The disadvantages, which seem to outweigh the advantages, are that there is a double chance of sepsis, and that the patient has to submit to two operations when one is sufficient. It is only performed by the author in cases in which there is a tendency to increased tension in the eye due to swelling of the lens in the early stages of the cataract. When a preliminary iridectomy is performed a keratome may be subst.i.tuted for the Graefe's knife in making the incision for the iridectomy, a much smaller one being necessary.
=Delivery of the lens by irrigation.= McKeown removes the soft lens matter by a process of irrigation into the anterior chamber, a practice not yet much adopted, but of considerable service in removing the soft matter after the extraction of the nucleus, especially in immature cataract. It is also probable that the thorough removal of the soft lens matter by this method reduces the number of cases of cyc.l.i.tis following the operation, since the soft matter forms a suitable medium for the growth of organism. The apparatus used is shown in Fig. 100, nozzle No.
2 being the most useful; it is inserted into one angle of the wound and a stream of sterilized normal saline solution at 39C. (in the flask) is allowed to flow into the anterior chamber; this stream is obtained by raising the flask until sufficient pressure is obtained. An undine may be subst.i.tuted for the flask. Care should be taken that there is a free return of fluid from the anterior chamber; irrigation should be continued until as much as possible of the soft matter has been removed.
=Extraction of the lens in its capsule.= This operation is frequently performed in India, where patients will often not return for needling of secondary cataract (capsulotomy). Although the method undoubtedly yields good results, the percentage of eyes damaged by loss of the vitreous must be higher than when the posterior capsule of the lens is left intact. The operation may be performed with or without an iridectomy, the lens being removed by pressure on the cornea with a large strabismus hook. If the vitreous should present, the lens should be removed with the vectis.
Extraction of the lens in its capsule is also performed when the lens is dislocated and causing irritation. If the lens be in the anterior chamber immediate extraction is called for, as glaucoma is a usual complication. Eserine is first instilled in order to contract the pupil and prevent the lens pa.s.sing back into the posterior chamber; an incision is then made as for a cataract extraction and the lens removed by means of the vectis. Complete dislocation of the lens into the vitreous rarely requires operation, as the patient is able to see.
Partial dislocation (luxation) occasionally calls for extraction, the vectis usually being employed for delivering the lens, but before undertaking the operation an attempt should be made to get the lens into the anterior chamber by dilating the pupil and making the patient lie face downwards; if this is successful eserine should be instilled to contract the pupil behind the lens and so retain it in the anterior chamber, from whence it can more easily be extracted. Some surgeons prefer to fix the lens with a needle pa.s.sed through the sclerotic behind the ciliary body before making the incision.
=Subconjunctival extraction.= In order to diminish the risks of sepsis, more especially in cases in which the conjunctiva is affected with trachoma, some continental surgeons deliver the lens into a pocket beneath the conjunctiva, whence it is subsequently removed. The operation has the additional advantage of a better blood-supply to the corneal flap, which is also held in better position after the operation.
_Operation._ A section upwards is made with a Graefe's knife as in the ordinary method of extraction previously described, the lens capsule being opened with the point of the knife as it is pa.s.sed across the anterior chamber. When the section through the sclerotic has been completed and the knife lies entirely beneath the conjunctiva it is withdrawn.
The wound in the conjunctiva on the outer side is then enlarged upwards with scissors, and an iris spatula is pa.s.sed beneath the conjunctiva from the small wound on the inner side and the point made to appear in the wound on the outer side; by this means the conjunctiva is raised on the spatula, and by means of sharp-pointed scissors a pocket is made in an upward direction by undermining the conjunctiva (Fig. 101). Delivery of the lens is then performed into this pocket, from which it is subsequently removed, the conjunctival wound on the outer side being closed with a st.i.tch. The advantage of this form of subconjunctival extraction over other forms which have been devised is that if difficulty is met with in delivering the lens, &c., the operation can be readily converted into an ordinary extraction by completing the division of the conjunctival flap.
[Ill.u.s.tration: FIG. 101. SUBCONJUNCTIVAL EXTRACTION. The section in the sclerotic being completed with a Graefe's knife, the figure shows the method of undermining the conjunctiva to form a pocket into which the lens is delivered and from which it is subsequently removed.]