STRABISMUS. 119 



STRABISMUS. 



Strabismus or Squinting is the want of harmonious action of the 

 muscles of the eyeball. It may be caused by the 

 overaction or the paralysis of a muscle. The or- Fig. 48. 



dinary varieties are the convergent, looking in- 

 wards, and the divergent, looking outwards : the 

 former is the more frequent. It may be congenital, 

 but usually occurs in childhood. Sometimes it is 

 the result of imitation ; or it may be induced by 

 marks or patches on the nose ; but oftener it is oc- 

 casioned by gastric or intestinal irritation. Cerebral 

 disturbance is another cause, especially when the squint 

 does not come until adult age. 



Treatment. — In childhood, where squinting depends 

 on sympathetic disturbance, it is often removed by pur- 

 gatives, alteratives, or anthelmintics. 



Some cases of squinting may be cured by division 

 of a muscle, but not all ; in fact, a deformity sometimes 

 results from the operation. 



In almost all cases of squinting, there is defective 

 vision in the affected eye ; this defect is usually relieved 

 when the operation is properly performed. The patient 

 should be steadied, as for other ophthalmic operations. 

 The eyelids are to be separated by an assistant or 

 speculum, and the eye not to be operated on is carefully 

 to be bandaged. 



The conjunctiva is to be seized by a small toothed 

 forceps, about midway between the cornea and the ca- 

 runcle, so as to form a horizontal fold, which is to be 

 snipped by the scissors close to the forceps, and between 

 them and the cornea ; or, this fold of conjunctiva may 

 be divided by an iris knife. After the division, the con- 

 junctiva is to be separated from the sclerotica for a slight 

 distance. The third step consists in the introduction of 

 a blunt hook, which is curved so as to accommodate it- 

 self exactly to the curvature of the eyeball. The hook 

 is to be passed under the tendon, from above downwards ; 

 and the muscle now being secure, it is to be divided by 

 a pair of scissors. If the pupil is now in the centre of 

 the orbit, and if the patient cannot turn the eye hori- 

 zontally inwards, the operation may be considered as 

 complete. Should a portion of the muscle, or some ten- 

 dinous fibres remain undivided, they are to be sought 

 for by the blunt hook, and divided. If the fascia is too 

 extensively divided, the eye will become too prominent, 

 or an external squint will result. 



