=Instruments.= Giant magnet (Fig. 126), steel spatula. (Watches and magnetizable metal should be removed from both the patient and the surgeon.)

=Operation.= Under atropine and cocaine. The patient is at first seated in a chair some three feet in front of the magnet, the eyelids being held apart by the surgeon; the electric circuit is closed. The patient's head is next gradually advanced towards the magnet. If a foreign body be present in the eye and be magnetizable, the patient will usually withdraw his head or cry out with pain, and the foreign body may be seen bulging forward the iris from the posterior chamber. From this position it may be removed by manipulating the head and eye in relation to the magnet so as to withdraw it into the anterior chamber, from whence it is removed through the entrance wound or an incision at the limbus either by the giant magnet directly applied to the wound or by magnetizing a steel spatula which is inserted into the anterior chamber and connected with the magnet by a flexible steel cable. The small magnet previously described may be used, or the foreign body removed by means of iris forceps.

[Ill.u.s.tration: FIG. 126. LARGE ELECTRO-MAGNET. The current is turned on by means of the foot pedal.]

A piece of steel in the vitreous always travels round the posterior surface of the lens and through the suspensory ligament, and does not injure the lens capsule.

=Complications.= These are similar to those described under the small magnet operation.

CHAPTER V

OPERATIONS UPON THE CORNEA AND CONJUNCTIVA

OPERATIONS UPON THE CORNEA

REMOVAL OF A FOREIGN BODY FROM THE CORNEA

Removal of a foreign body from the cornea requires a good light (focal illumination). The use of a binocular lens is also of service. Foreign bodies lodged on the surface of the cornea can be removed easily under cocaine with a spud. If the foreign body be deeply embedded in the cornea a fine sterile discission needle should be used. When a foreign body, such as a chip of iron, is deeply embedded, the needle should be inserted slightly to one side of the entrance wound and pa.s.sed beneath the foreign body so as to lift it from its bed. When the foreign body has partially penetrated the anterior chamber but still lies in the cornea, an incision should be made with a keratome at the limbus and the foreign body pushed back through the entrance wound with the aid of an iris spatula. If the foreign body be iron, the electro-magnet may be of use, and in this case should be tried before resorting to an incision in the anterior chamber. A stain is left frequently after the removal of foreign bodies; this should be removed as far as possible. Subsequently the eye should be bandaged for a few days and bathed with boric lotion.

Atropine should be instilled if there be any signs of infiltration around the wound.

CAUTERIZATION OF THE CORNEA

Either a chemical or the actual cautery may be used.

=Indications.= _Corneal ulceration._ The cornea being extremely dense, organisms do not penetrate very deeply into its substance, so that destruction of the bacteria is effected by cauterization of the spreading portion of an ulcer; the alb.u.min is also coagulated and so a barrier is presented to their advance.

=Operation.= The eye is thoroughly cocainized, and the spreading portion of the ulcer is first defined by staining with fluorescine, washing away the excess of stain with boric lotion.

_By a chemical caustic._ Liquefied carbolic (carbolic acid crystals liquefied in 10 per cent. of water) is applied upon a sharpened match.

Any excess should be removed so as to prevent its running on to the cornea. A speculum is inserted and the cornea is dried by blotting with cigarette paper; the stained area is lightly touched with the point of the stick, particular attention being paid to the spreading margin. A dense white plaque is the result; this usually clears up in a few days.

Atropine ointment is applied daily to the conjunctival sac.

[Ill.u.s.tration: FIG. 127. ELECTRO-CAUTERY.]

_By the actual cautery._ The electro-cautery (Fig. 127) point should be extremely fine and only raised to a dull red heat. The stained area should be touched lightly with the point.

The actual cautery is best for serpiginous corneal ulcers, carbolic acid being more satisfactory for those of the vesicular type.

OPERATIONS FOR CONICAL CORNEA

=Indications.= Since the operation for conical cornea is not without serious risks, it should only be undertaken when the vision cannot be improved with gla.s.ses to 6/18; high + or - cylinders will often yield satisfactory results. The object of all forms of operation is the flattening of the cone.

=Operation.= This may be carried out either by excision of the apex of the cone or by cauterization.

=Excision of the apex of the cone= is probably the more satisfactory method, although it is somewhat more difficult to perform. The object of the operation is to remove an elliptical portion of the whole thickness of the cornea from the apex of the cone, the long axis of the ellipse being placed horizontally. It leaves the eye with only a minute scar as compared with the nebula produced by the cautery, which is often so great as to require an optical iridectomy to restore vision.

=Instruments.= Speculum, fixation forceps, a narrow Graefe's knife, straight iris forceps, and scissors.

The operation is done under cocaine, atropine having been previously instilled.

_First step._ The apex of the cone is transfixed by the Graefe's knife with the blade directed slightly upwards and forwards, the knife being made to cut out. The cornea in this situation is extremely thin, being often not more than 1 mm. in thickness. The length of the incision should not exceed 2 mm.

_Second step._ The flap of corneal tissue thus made is seized with the straight iris forceps and removed with iris scissors, producing a small elliptical opening. The chief difficulty of the operation is the seizing of the corneal flap, which is most difficult to hold; care must be taken not to injure the lens capsule with the iris forceps or scissors when the cornea has collapsed as the result of the evacuation of the anterior chamber. The eye should be firmly bandaged subsequently, and the patient kept in bed until the anterior chamber has re-formed.

=Complications.= _Slow re-formation of the anterior chamber._ The anterior chamber will often take two or three weeks to re-form, owing to the hole in the cornea not closing. During this time the eye is open to septic infection and therefore the greatest care should be taken to keep it aseptic when dressing it. For this reason and also because the following complications are due to the same cause, it is desirable to remove as little corneal tissue as possible in performing the operation.

It is probable that conjunctivoplasty (see p. 245) would considerably facilitate the rapid closure of the wound.

_Anterior polar cataract_ may result from prolonged contact of the lens with the wound in the cornea. As a rule this seldom interferes much with vision.

_Anterior synechiae_ from incarceration of the iris in the wound occasionally result and may require subsequent division.

_Acute glaucoma_ is by no means an infrequent complication--indeed the author has seen four successive cases of conical cornea, operated on both by excision and by the cautery, followed by this complication. It is probably due to adhesion of the root of the iris to the back of the cornea during the time the anterior chamber is empty. It can usually be relieved by an iridectomy.

=The electro-cautery operation.= The operation generally adopted is known as the target operation. It consists in surrounding the apex of the cone with two rings of cautery marks, the outer made at a dull red heat, the inner with the point slightly brighter, whilst the apex is cauterized at a red heat, so that rings of different depth are obtained.

Cauterization of the apex should stop just short of perforation, the inner ring being deeper than the outer. With this method secondary glaucoma and anterior synechiae are not so liable to occur. On the other hand, an optical iridectomy has to be performed more frequently. A few surgeons still cauterize the apex of the cone until a perforation is produced. This latter operation seems to have the disadvantages of both methods and the advantages of neither.

REMOVAL OF TUMOURS INVOLVING THE CORNEA

Tumours which involve the cornea are usually secondary to tumours occurring at the limbus. The chief of these are: _simple_--dermoid patches, moles of the limbus; _malignant_--sarcoma, endothelioma, epithelioma. Dermoid patches should be shaved off as close to the cornea as possible; the white area left after their removal can be improved by tattooing.

Malignant tumours in very early stages may be removed locally with scissors and forceps, the cautery being applied to their base, since they do not tend to invade the sclerotic deeply.

TATTOOING THE CORNEA

=Indications.= (i) To do away with the blinding effects of light through a scar after iridectomy has been performed (see p. 215).

(ii) To simulate a pupil on a white scarred cornea.

[Ill.u.s.tration: FIG. 128. TATTOOING NEEDLES.]

The operation is not without risks, as it may light up old inflammation in a previously quiet eye. Panophthalmitis and sympathetic ophthalmia have both been known to follow it. The p.r.i.c.king of the needle may carry in epithelium and implantation dermoids may arise.

=Instruments.= A fine single needle is generally used, occasionally a bundle of needles (Fig. 128).

=Operation.= Under cocaine. Chinese ink, sterilized and prepared by rubbing up with 1-6,000 perchloride of mercury, is smeared over the area to be tattooed. Multiple punctures in an oblique direction are then made into the cornea over the area desired. More paste is then rubbed in over this area. The cornea should be intensely black after the operation, as a certain amount of the ink is carried away by phagocytosis and shedding of the epithelium. Subsequent reaction may be reduced by means of an iced compress. Atropine should be instilled.

Sc.r.a.pING CALCAREOUS FILMS

Calcareous films, when not a.s.sociated with active irido-cyc.l.i.tis, may be removed with advantage to the vision. Care should be taken to see that no kerat.i.tis punctata is present before the operation is undertaken.