Part 40 (1/2)

After all operations upon the ocular muscles both eyes should be occluded to keep the eyes at rest whilst the muscle is gaining its fresh attachment to the globe; this usually takes about seven days, after which time both eyes should be uncovered, and if there is a tendency to convergence atropine should be used. Gla.s.ses correcting any error of refraction should be worn.

TENOTOMY

Tenotomy may be performed by (1) the open, or (2) the subconjunctival method.

=Instruments.= Speculum, straight blunt-pointed scissors, strabismus hook, needle and silk, needle-holder.

=Operation.= The operation is performed under adrenalin and cocaine.

1. _By the open method._ The surgeon stands on the right side facing the patient when dividing the right external or the left internal rectus, but at the head of the table when dividing the right internal or the left external rectus.

_First step._ The speculum is inserted and the patient is made to look away from the muscle to be divided. The conjunctiva is freely divided vertically with scissors directly over the insertion of the tendon into the globe (see Fig. 130) and dissected backwards.

[Ill.u.s.tration: FIG. 130. TENOTOMY. Showing the method of holding the scissors and the position of the hands.]

_Second step._ The tendon of the muscle is then seized with fixation forceps and b.u.t.ton-holed about its centre as close to the globe as possible (Fig. 131). The lower blade of the scissors is then pa.s.sed through the hole in the tendon, and the rest of the tendon and its expansions are divided upwards and downwards to the extent required to bring the eye straight as tested by its appearance or by the Maddox rod test. The strabismus hook may be inserted, both upwards and downwards, to see that the tendon is properly divided, but all pulling on the muscle with a hook should be avoided, as it is painful and disturbs the muscular equilibrium. The conjunctiva is then brought together with a fine silk suture. If the squint be over-corrected by the tenotomy, a deep hold should be taken with the st.i.tch so as to draw the eye back into position.

2. _By the subconjunctival method._ This is unsatisfactory in that accurate adjustment by division of the expansion of Tenon's capsule is not possible. It is painful, and is sometimes followed by a troublesome haemorrhage into the capsule of Tenon. Occasionally it may be of use in some cases of amblyopic eyes where a small wound is desirable. The conjunctiva is b.u.t.ton-holed below the tendon, and separated from the surface of the muscle. The capsule of Tenon is then opened below the tendon, a strabismus hook is pa.s.sed through the opening with its concavity against the globe, and is then rotated upwards beneath the tendon, which is subsequently divided between the hook and the globe.

[Ill.u.s.tration: FIG. 131. TENOTOMY BY THE OPEN METHOD. The tendon is first b.u.t.ton-holed about its centre and the expansions are then divided upwards and downwards to the required extent.]

=Complications.= These may be immediate or remote.

=Immediate.= 1. _Haemorrhage into the capsule of Tenon_, leading to intense proptosis, only occurs when the subconjunctival method is adopted. As a rule the haemorrhage ceases on the application of pressure, but occasionally it may be necessary to open up the wound and turn out the blood-clot.

2. _Perforation of the globe_ has been known to occur during the division of a tendon in an obstreperous patient. It should be treated as a wound of the sclerotic (see p. 235).

3. _Tenonitis_ very rarely occurs, but may lead to matting down of all the extra-ocular muscles and defective movements of the globe.

Panophthalmitis has been known to follow this condition.

=Remote.= 1. _Failure to correct the muscular error._ If the error be large it must be rectified by tenotomy of the corresponding muscle of the other eye or by the advancement of the opposing muscle of the same eye. This should not be undertaken until five or six weeks have elapsed since the previous operation.

2. _Over-correction of the muscular error at the time of the operation_ may be remedied by st.i.tching the tenotomized muscle forward to the extent required to bring the eye straight. Advancement of the tenotomized muscle should be performed if the over-correction be only discovered after the operation. In cases with binocular vision lesser degrees of deviation may be corrected with prisms if they are causing symptoms, while small errors of over-correction, of about 3 prism, often disappear after the first few weeks.

3. _Defective movement in the tenotomized muscle_ is usually present for the first week or two after the operation, but recovery usually takes place after the muscle has regained its attachment to the globe; it may persist, however, to a slight extent; this is most liable to occur after free division of the tendon and its expansion (more especially in the case of the external rectus), or because the tendon has not been divided close enough to the globe. In patients with previous binocular vision diplopia is present after the operation on turning the eyes towards the same side as the tenotomized muscle, but this usually disappears.

4. _A granulation_ may form at the site of the tenotomy wound. It may be due to a tag hanging from the wound or to a portion of a st.i.tch that has been imperfectly removed. It should be snipped off with scissors and the conjunctiva drawn together over its base.

5. _Proptosis_ may result from too free a division of a tendon.

6. _Retraction of the caruncle_ is best avoided by closing the conjunctival wound with a st.i.tch, and thus pulling the caruncle forward.

ADVANCEMENT

Advancement is an operation undertaken to rectify a squint by forming a fresh attachment for one of the ocular muscles nearer the cornea, and at the same time shortening it. There are three main types of operation performed:--

1. The capsulo-muscular, in which the tendon, together with the attachment of the capsule of Tenon to it, is advanced.