=Instruments.= Speculum, fixation forceps, a spoon which should have rather a blunt edge.

=Operation.= Under cocaine. The area is very lightly sc.r.a.ped with the spoon. The calcareous changes are in the deeper layers of the epithelium and Bowman's membrane and hence are easily removed. The sc.r.a.ping should be carried well beyond the apparent margin of the film. The epithelium often takes some time to regenerate. As a rule the results are satisfactory, although the film is apt to recur in the course of years, but it may be removed again if necessary.

OPERATIONS UPON THE CONJUNCTIVA

THE REMOVAL OF FOREIGN BODIES

Foreign bodies lodged in the conjunctival sac, unless embedded in the conjunctiva, are usually found by the surgeon under the upper lid, the sulcus subtarsalis being a favourite situation. They are easily removed with a spud or needle, after the instillation of a drop of 4% cocaine solution. Subsequently the eye should be bandaged for a few hours until the effect of the cocaine has pa.s.sed off, as in wiping the eye the patient may wipe off the epithelium of the cornea whilst it is insensitive from the cocaine.

_In order to evert the upper lid_ the patient is made to look strongly down, the eyelashes are seized between the thumb and forefinger of the left hand, the skin of the upper lid is pushed down above the tarsal cartilage with the thumb of the right hand, and the lid is everted by pulling it upwards against the point of the thumb.

OPERATION FOR PTERYGIUM

=Indications.= Pterygium should be removed when advancing across the cornea, especially when the pupillary area is becoming involved. The operation of ablation is the one now generally in use.

=Instruments.= Speculum, straight iris forceps, small sharp-pointed scissors.

=Operation.= Under adrenalin and cocaine the neck of the pterygium is seized with the forceps and the body and neck are carefully dissected from the conjunctiva. The body and neck should be very carefully separated right up to the corneal margin by means of forceps and scissors. The head is then stripped off the cornea with a sharp pull.

The wound in the conjunctiva should be subsequently closed with fine sutures, otherwise the disease will certainly recur. In stripping the head from the cornea some of the epithelium may be torn off with it.

This usually regenerates without impairing the vision.

EXPRESSION

This is an operation for the removal of follicular formations in the conjunctiva, and is used more especially in trachoma.

=Instruments.= Graddy's forceps (Fig. 129), fixation forceps.

=Operation.= The operation may be performed under cocaine and adrenalin, a little solid cocaine being rubbed into the area to be expressed. In severe cases in which both eyes are affected, and in small children, a general anaesthetic may be necessary.

Although a number of instruments are in use, perhaps the best, and certainly the least painful, is Graddy's forceps. In the case of the upper lid it is everted, one blade of the forceps being pa.s.sed into the fornix, the other being placed over the upper surface of the everted lid. A gentle steady pressure is applied, and the lid is drawn out between the blades. In this way as much of the conjunctiva is gone over as is necessary. The lower fornix is best expressed by picking up the loose fold of the fornix with ordinary forceps and then expressing with Graddy's.

[Ill.u.s.tration: FIG. 129. GRADDY'S FORCEPS.]

If only one or two follicles be present they can be picked up with the ordinary fine dissecting forceps and expressed, but when situated on the tarsus the follicles are best enucleated with a spud; a solution of 1 in 50 perchloride of mercury in glycerine is then rubbed into the conjunctiva. The operation may have to be repeated several times as new follicles form.

CONJUNCTIVOPLASTY

Conjunctivoplasty is an operation for the transplantation of a flap of conjunctiva to cover some loss of substance or defect in the continuity of the globe.

=Indications.= The operation may be necessary--

(i) To close large recent wounds of the cornea.

(ii) To close the wound made by the excision of a cystoid scar.

(iii) To facilitate the healing of a clean ulcer such as Mooren's ulcer, or to cover the aperture made by an ulcer that has perforated.

(iv) In the treatment of conical cornea by excision of the apex of the cone, it might facilitate the rapid closure of the wound and a.s.sist in flattening of the cornea.

=Operation.= _First method._ Under cocaine. A flap of conjunctiva is raised from around the limbus, having its base as near the area to be covered as possible; its breadth should be one and a half times the width of the area to be covered. This flap is drawn across the defect in the cornea and st.i.tched to the conjunctiva on the other side; the wound made in raising the flap should be allowed to heal by granulation.

The st.i.tches holding the flap in position cut through in two or three days, but by that time their purpose will have been served. If the flap be still adherent to the wound its base may be divided and any superfluous tissue removed; the remainder will disappear rapidly.

_Second method._ The conjunctiva is dissected up all round the cornea as close to the limbus as possible, and backwards as far as the insertion of the recti. A purse-string suture is then inserted around its margins and drawn tight so that the whole cornea is covered by conjunctiva. The operation is suitable for cases in which large areas have to be covered.

REMOVAL OF TARSAL CYSTS

The Meibomian glands being embedded in the tarsal plate, cysts in them present both on the conjunctival surface and towards the skin, but the contents are always evacuated from the former.

=Instruments.= Walton's iris knife, sharp spoon.

=Operation.= Under adrenalin and cocaine. The eyelid is everted and a drop of the solution is injected into the cyst with a hypodermic syringe. A vertical stab is made into the cyst with the knife and the contents are then evacuated with a sharp spoon.

Difficulty may arise in fixing the cyst whilst making the incision; this is best obviated by holding the everted lid between the finger and thumb.

In some cases, when the cyst has persisted for a considerable time, the sac-wall becomes so thickened that it has to be dissected out before the ma.s.s in the lid will disappear.

CHAPTER VI

OPERATIONS UPON THE EXTRA-OCULAR MUSCLES

SQUINT OPERATIONS

=Indications.= Operations upon eyes with concomitant squint are undertaken for two purposes:--

(i) For cosmetic reasons, to remedy a deformity due to a squinting eye which is amblyopic.

(ii) To rectify the muscular equilibrium in alternating or latent squints, so that binocular vision may be regained.

When the operation is performed for the latter reason the adjustment will naturally have to be much more accurate than for the former, so as to bring about the superimposition of the images falling on each macula.

The muscular balance is interfered with by the administration of a general anaesthetic, and therefore the results cannot be gauged accurately. Thus it is desirable that operations upon the ocular muscles should be performed under local anaesthesia. This is usually possible, except in the case of very small children.

During and after the operation muscular equilibrium is tested by means of an electric light fixed to the ceiling immediately over the head of the patient (see Fig. 74). The room is darkened and the patient is made to look at the light. In a case with an amblyopic eye the reflection of the light should appear in the middle of each cornea if the eye be properly adjusted. In cases where good vision is present in both eyes the Maddox rod test should be used, the rod being placed before the eye not being operated on; the bar of light produced by the rod should pa.s.s through or within a few inches of the light if the adjustment has been performed accurately.

The tendons of the recti muscles are inserted into the globe at the following distances from the corneo-sclerotic junction: internal, 5 mm.; inferior, 6 mm.; external, 7 mm.; superior, 8 mm. Each muscle is held in place by expansions on either side of the tendon as well as by the tendinous insertions. Division of these expansions allows a greater retraction of the muscle and is, therefore, to be undertaken when a considerable degree of squint has to be overcome. On the other hand, there will be a danger that the muscle may not regain a proper attachment to the globe if division be too freely performed, and a squint in the opposite direction may result; proptosis also may be caused thereby. It is, therefore, better to combine tenotomy with advancement in high degrees of squint over twenty degrees convergent and in all cases of constant divergence. This is usually better than performing a tenotomy in the other eye, as there still remains the muscle of the other eye in reserve to tenotomize if necessary, if the advancement be insufficient to correct the squint. Further, it is much easier to rectify a muscular error by accurate tenotomy than by advancement. Division of the tendon of the internal rectus only, without its expansion, will usually rectify cases of latent convergent strabismus with a deviation of about 12 prism (Maddox test). Cases of latent divergent strabismus of about 8 prism (Maddox test) require complete division of the tendon of the external rectus, and, in some cases, of the expansion as well. Tenotomy of the superior rectus for hyperphoria should only be undertaken in bad cases; that is to say, of over 12 prism, any lateral deviation being first corrected, as occasionally the correction of the lateral deviation, especially when this is due to the faulty insertion of a muscle, will sometimes correct the hyperphoria present.

Partial tenotomies are performed by some surgeons for the correction of latent muscular errors, but the experience of most in this country is that little benefit is gained unless the tendon be completely divided.

Tendon-lengthening by various methods has been performed, but has not come into general use.