Squint : its causes, pathology and treatment / by Claud Worth.

  • Claud Worth
Date:
1903
Catalogue details

Licence: In copyright

Credit: Squint : its causes, pathology and treatment / by Claud Worth. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    is intolerable. Sometimes, however, owing to a congenital defect, the fusion faculty develops later than it should, or it develops very imper- fectly, or it may never develop at all. Then, in this case, there is nothing but the motor coordinations to preserve the normal relative directions of the eyes, and anything which dis- turbs the balance of these coordinations will cause a permanent squint. Thus the essential cause of squint is a defect of the fusion faculty. In the presence of this fundamental cause, the eyes are in a state of unstable equilibrium, ready to squint either inwards or outwards on slight provocation. This provocation may be supplied by:- (i) Hypermetropic!,. — As already explained, uncorrected hypermetropia causes a tendency to abnormal dynamic convergence of the visual axes. In the vast majority of cases of hypermetropia the fusion sense is perfect, so that this tendency is kept in check and the child does not squint. If, however, the fusion sense is deficient, the eyes are free to yield to this tendency, and a convergent squint is established. In the cases in which hypermetropia is the immediate exciting cause, the abnormal convergence is at first entirely dyna- mic, static convergence being nil. The squint is at first occasional—when the child is looking at nothing in particular, relaxing the accom-