Keeping the ca.n.a.l relaxed by relaxing his hold on the lid, the surgeon now gently wriggles the probe along the ca.n.a.liculus, gradually stretching it as the probe advances, so as to avoid catching of the sides of the ca.n.a.l before the point of the instrument, till he is satisfied that it has fairly entered the nasal duct. He then stretches the eyelid, brings the handle of the probe out over the cheek so as to evert the punctum as much as possible, and then with a fine sharp-pointed knife enters the groove (Fig. IX.), and fairly slits up the punctum and the ca.n.a.l to the full extent. The incision should be as straight as possible, and through the upper wall of the ca.n.a.liculus. A dexterous turn of the instrument upwards on the forehead will generally enable it to be pa.s.sed at once fairly into the nose through the nasal duct, the usual rule being observed of pa.s.sing it downwards and slightly backwards, the handle of the probe pa.s.sing just over the supraorbital notch.

[Ill.u.s.tration: FIG. IX.[84]]

For several days after the operation the probe will have to be pa.s.sed, both to prevent the wound in the ca.n.a.liculus from healing up, which it is too apt to do, and also to gradually dilate the nasal duct if it has been previously strictured. Probes and directors of various sizes are required; in fact very much the same instruments (in miniature) as are required for the treatment of stricture of the urethra.

Mr. Greenslade has invented a very ingenious little instrument, of which, through his kindness, I am able to show a woodcut (Fig. X.), for slitting up the ca.n.a.liculus without having to fit the knife in the groove.

[Ill.u.s.tration: FIG. X.]

PTERYGIUM, the reddish fleshy triangular growth, with its base at the inner canthus, and its apex spreading to and often over the cornea, requires invariably a small operation for its removal. In most cases it will be found sufficient merely to raise the lax portion over the sclerotic with forceps, and divide it freely, removing a transverse portion. If it has encroached upon the cornea, the portion interfering with vision must be dissected off with great care and removed.

In some cases, however, it has been found that after removal of a large pterygium, a retraction of the caruncle and the semilunar fold is apt to take place, which renders the eyeball unpleasantly prominent. To avoid this the pterygium may be carefully dissected up from its apex to near its base, and then displaced laterally either upwards or downwards, its apex and sides being st.i.tched to a previously prepared site of conjunctiva.

OPERATION FOR CONVERGENT STRABISMUS.--_Division of the internal rectus._--_Subconjunctival operation._--The spring-wire speculum (C) separating the lids, the surgeon divides the conjunctiva by a pair of scissors in a horizontal line (Fig. XI. A A) from the inner margin of the cornea, a little below its transverse diameter to the caruncle, then snipping through the sub-conjunctival tissue, he pa.s.ses a blunt hook bent at an obtuse angle under the tendon of the internal rectus, and endeavours by depressing the handle to project the point of the hook at the wound. Then with successive snips of the scissors he divides the tendon on the hook, close to its sclerotic margin. Lest it should not be freely divided, various dips with the hook may be made to catch any stray fibres left untouched; but very great care should be taken not to wound the conjunctiva beyond the first horizontal cut in it. The tendon being divided satisfactorily, the edges of conjunctiva should be replaced, and the eye closed for a few hours.

[Ill.u.s.tration: FIG. XI.[85]]

The original operation of Dieffenbach, now rarely practised, consisted in making an incision, B B, across the tendon, then, by cutting the areolar tissue exposing the insertion of the tendon, and dividing it freely; after which the sclerotic in the neighbourhood was to be cleaned and any band of fibres divided. There are risks on the one hand of a most unseemly exophthalmos with divergent squint, and on the other of a retraction of the semilunar fold, so that the sub-conjunctival operation is always preferable.

OPERATIONS FOR DIVERGENT SQUINT.--This very serious deformity is often the result of the operation for convergent squint, and is a.s.sociated with a fixed, leering, and prominent eye, and frequently with most annoying double vision.

1. In a simple case of primary divergent strabismus (very rare) it is sufficient simply to divide the external rectus in the manner already described for division of the internal.

2. If secondary to an operation for convergent squint, the indication is to restore the cut internal rectus to a position on the sclerotic a little behind its previous one, as the cause of the divergence is found in a complete detachment of the internal rectus. This is attempted in various ways.

(1.) _Jules Guerin_ carefully divided the conjunctiva over it, and sought for the remains of the internal rectus, freeing it from its attachments. He then pa.s.sed a thread through the sclerotic on the _outer_ side of the globe, and by pulling on it and fixing it across the nose, rotated the eye inwards, in the hope that the remains of the internal rectus would secure a new attachment.

(2.) _Graefe's modification_ of this is more certain. Without any minute dissection he merely separated the internal rectus, along with the conjunctiva, and fascia over it, so that it can be pulled forwards, then cut the external rectus, and inverted the eyeball to a sufficient extent by means of a thread pa.s.sed through the portion of the tendon of the external rectus, which remains attached to the sclerotic. The risk of all these operations, in which both muscles are divided, is protrusion of the eyeball from the removal of muscular tension.

(3.) _Solomon's operation for the radical cure of extreme divergent strabismus_,[86] is at first sight a very curious one. Without going into all the details, the steps are as follows:--

_a._ A square-shaped flap, with its attached base at the nasal side, is raised, containing the remains of the inner rectus and its adjacent parts.

_b._ A flap similar in shape and size, but different in the position of its attached base, is made on the other side of the cornea. It is made by dividing the external rectus just behind its tendon, and then reflecting forwards the tendon with its conjunctiva.

_c._ These two flaps are united over the vertical meridian of the cornea by sutures, three generally being sufficient. This entirely hides the cornea for a time, but eventually shrivels and contracts, and the remnants are to be cut off with scissors three weeks after the operation.

PUNCTURE OF THE CORNEA.--_Paracentesis of the Anterior Chamber._--_Tapping of the Aqueous Humour._--This very simple operation is in many cases extremely useful. In cases of corneal ulcer, the result either of injury or disease, where there is much pain in the bone, and evidence of tension of the globe, it gives great relief, and when repeated at short intervals greatly hastens a cure. Sperino of Turin recommends its frequent use in cases of chronic glaucoma.

_Operation._--The surgeon stands behind the patient, who is seated; the lids being fixed, the upper by the surgeon's left hand, and the lower by an a.s.sistant, the cornea is punctured a little in front of the sclerotic margin, either with a broad needle, or, what is as good, a well-worn Beer's knife. Care must be taken on entering the knife, on the one hand, not to wound the iris, which is sometimes arched forwards in the cases of commencing glaucoma, and, on the other, fairly to enter the anterior chamber, not merely split up the layers of the cornea. On withdrawing the cataract knife, the aqueous humour gets out by its side, aided by a slight turn of the knife, sometimes with great force, and in much larger quant.i.ty than usual. If the operation has been done by a needle, a blunt probe requires to be introduced on the removal of the needle. Once punctured, the remarkable fact is that the same wound suffices for many succeeding tappings, which are effected by pressing the probe into the wound day after day, sometimes several times a day, with great relief to the symptoms. If the probe is to be used for succeeding evacuations, the operator must be careful to remember the exact spot at which the needle or knife was entered. To facilitate remembering it, it is best, when nothing prevents it, to operate always in the same spot. Sperino chooses the horizontal meridian of the cornea at the temporal side, at the junction of the cornea and sclerotic.

CATARACT OPERATIONS.--Here we cannot enter into any discussion of the pathology of cataract and the varieties of it. Enough for our purpose to know that the lens is in some cases hard, in others soft, and that thus in the latter it may be removed piecemeal, and by a small incision, while in the former, removal must be almost entire, and by a larger opening.

In cataract, the lens, which should be transparent, has become opaque, and the object of treatment is to get it out of the line of sight, to prevent it from obstructing, now that it can no longer a.s.sist sight.

The operations used for this end may be cla.s.sed under three heads:--

1. _Operations for the removal of the lens out of the way without its removal from the eye._--These used to be extensively practised under the name couching, and are of two kinds,--_Depression_, where the lens is simply pushed down from its place by a needle; _Reclination_, in which it is shoved backwards (turning on its transverse axis) as well as downwards. These are relics of old surgery, and very rarely practised by any oculists of eminence, as, though easy to perform, and with very flattering immediate results, the risks of chronic inflammation of the whole globe and injury to the retina are very great.

2. _For solution._--THE NEEDLE OPERATION.--Suitable (among other cases) especially in congenital cataracts in infants, and in cases of diabetic cataract.

The principle of this operation is that the lens, once the capsule is freely opened in front and the aqueous humour admitted, is found rapidly to become absorbed and disappear, if the cataract has been a soft one.

_Operation._--A needle with a lance-shaped head is to be used. It should be so made that the rounded shaft of the needle is just large enough to play freely in the wound made by the broader point, and yet not so small as to allow the aqueous humour to escape rapidly. The pupil has been dilated, the patient is lying on his back, and the globe is fixed by forceps attached to the conjunctiva of the inner side of the eye, and held by an a.s.sistant. The surgeon then enters the needle close to the sclerotic margin of the cornea, carries it fairly on in the anterior chamber, till the centre of the pupil is reached. He then, by bringing forward the handle, projects the point backwards against the anterior capsule, which he freely lacerates with the point and edge in several directions.

In infants, where processes of repair go on very rapidly, the whole lens may be freely broken up. In diabetic cataract, or indeed in all cases of solution, where the patient is adolescent or adult, or the eye at all weak, only a small portion of the lens should be attacked at one sitting.

The needle should then be withdrawn gradually and with great care, that the broad axis of the blade be in exactly the same position in which it entered, _i.e._ flat and parallel with the iris, lest the iris be wounded, entangled, or prolapsed.

The eye is then to be closed for twenty-four hours; if there is much pain, atropia must be freely used.

_Varieties in the Operation._--Some use two needles at once for breaking up the lens. Some surgeons prefer to enter the needle through the sclerotic; this complicates the operation and renders it less certain, as the point of the needle is of course out of sight in its progress between the iris and the lens.

Even in children this operation requires in most cases to be repeated at least once, while in adults it may be required at short intervals for many months.

3. _By Extraction._--In these operations the lens is at once removed from the eye--

(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 reacc.u.mulates.

[Ill.u.s.tration: FIG. XII.]

[Ill.u.s.tration: 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.

Certain points require attention:--1. That the puncture to admit the curette is large enough; 2. That its end be sufficiently rounded; 3. Its open end must be held in the area of the pupil, and not allowed to pa.s.s behind the iris, else there is great risk of the iris being drawn in. Among other advantages claimed by its inventor, the chief seems to be a more thorough removal of the lens than by the ordinary means, and consequently less risk of opaque deposit in the posterior capsule.

(2.) EXTRACTION BY FLAP.--When properly performed in a suitable subject, and when free from accident, this operation is one of the most thoroughly beautiful and satisfactory in the whole domain of surgery; but it is difficult, and liable to many risks which neither skill nor caution can completely guard against.

It is required in many cases of hard cataract, which are amenable neither to solution nor linear extraction.

_Operation_ must be considered in various stages:--

_a._ To make a flap of cornea large enough to permit of the removal of the entire lens without pressure or bruising. To make it of cornea only, to prevent the escape of the vitreous, and to avoid injury of the iris.