Prognosis in cases of strabismus with special reference to orthoptic treatment.

WHEN orthoptic treatment was first practised it was thought that, if it were applied in cases of non-paralytic strabismus where there was good visual acuity in each eye, restoration of normal binocular function would invariably result. In the early 1930s it was not unusual for children suffering from squint to be subjected to countless sessions of treatment with reflecting stereoscopes in the hope of establishing fusion. It was not until Chavasse (1939) published his theories with regard to the binocular reflexes and their development, that the true limitations of orthoptic treatment became more widely recognized. The important fact then emerged that, the earlier the onset of a constant strabismus and the longer the interval of time before corrective treatment is carried out, the less likely is it that normal binocular function will be restored, no matter how much orthoptic treatment is given. Experience with a large series of cases of strabismus and the study of the work of Chavasse have taught us that in certain cases binocular single vision cannot be attained whatever the treatment, while in others, provided the, correct treatment is given, the restoration of binocular single vision is certain. Thus, statistics regarding the results of treatment in terms of binocular function are quite meaningless unless they contain information about the types of case under review. The correct treatment varies according to the type of case; it may consist merely of appropriate spectacles (with or without the assistance of orthoptic treatment), or of surgical treatment (with or without the assistance of spectacles and orthoptic treatment), or of orthoptic treatment only. Despite these facts, in many clinics a routine course of orthoptic treatment is still recommended and carried out indiscriminately in all cases of non-paralytic strabismus. The result is that a large percentage of patients treated by orthoptic measures fail to regain normal binocular function. The conclusion is drawn that in these cases orthoptic treatment has failed, as indeed it has, but the failure is due to its employment where it was not indicated. After studying the history of a case of strabismus and after carrying out a thorough examination, it should be possible in most instances to decide