Anomalous Sensory Relationship in Apparently Cured Squints

DURING the last few years it has been found that many patients presumed to have normal binocular single vision after optical, orthoptic, and/or surgical treatment, have in fact a small angle of anomaly. From certain points of view this is not of great importance, as such cases are satisfactory cosmetically, and show good visual acuity in each eye with a limited degree of fusion detectable by certain tests. On the other hand, the amplitude of fusion is invariably restricted and true stereopsis is absent, and this is an unfortunate state of affairs in these days when normal binocular function is required in an increasing number of professions. Even if (in common with some authors) we decry the value of stereopsis, there remain the risks associated with a small range of fusion-secondary divergence and the gradual establishment of amblyopia. It is not unusual to encounter heterophoria of as much as twelve degrees, which, if associated with good fusion, causes no subjective symptoms. By contrast, quite low degrees of heterophoria, if associated with lack of fusion, may lead to intermittent or permanent decompensation. This is not meant to imply that our standards are so high that our poorest results are those in which the residual angle is so small as to be hardly detectable by the ordinary methods of measurement; on the contrary, we classify such cases as "successful failures". An analysis of these results, however, suggests that perhaps these small residual angles might have been avoided, and perhaps also that, from the strictly sensory viewpoint (because it is harder to improve the sensory relationship in a case with a small angle of anomaly than in one with a large angle), we have made matters worse by treatment.