Development of Normal Binocular Vision in Early Convergent Strabismus after Orthophoria.

A fundamental difference exists, from the sensory viewpoint, between the cases of constant squint developing before the third year of life and all the other forms of oculomotor imbalance. The first group is the one considered in the literature as that of "strabismus with anomalous correspondence". Must we consider the "anomalous correspondence" of these subjects as a system of corresponding retinal points similar in its organization to normal correspondence? A great divergence of opinion and of statistical evidence with regard to this problem is found in the literature; we think that these discrepancies may be easily explained by the fact that different and unnatural tests were used to assess the state of retinal correspondence. The systematic examination of squinting subjects in normal surroundings (tests with striated glasses) allows certain conclusions to be drawn for subjects under 10-12 years of age: (1) The occurrence of a definite post-operative diplopia or a relapse of the original angle of deviation is exceptionally rare in these subjects; this would not be so if anomalous correspondence was a rigid system comparable to that of normal correspondence. Moreover, anomalous retinal correspondence only rarely forms the sensory basis for the compensation of a small oculomotor imbalance (rare fusional movements) (Maraini and Pasino, 1964). (2) Anomalous retinal correspondence adapts itself easily and rapidly to the changed angle of deviation brought about by surgical treatment. It would seem that, in the absence of amblyopia or of deep suppression, the sensory behaviour in normal surroundings depends chiefly on the position of the eyes (Pasino and Maraini, 1964). As this is changed by surgery to very small angles (without vertical deviation) the anomalous binocular vision of these subnormal conditions is characterized by harmonious anomalous retinal correspondence with fusion, a fusional amplitude nearly exclusively based on variations of the anomaly and only rarely on fusional movements (Maraini and Pasino, 1964), and a coarse stereopsis with very low stereoscopic acuity (Pasino, Maraini, and Santori, 1963). If orthophoria is obtained (with prisms, for instance) one would expect this sensory situation to become converted into a normal binocular localization (Bagolini, 1961). In the last few years we have had the opportunity of treating and following up for a sufficient interval of time a certain number of these patients. All of them had a fixed convergent strabismus of very early onset with anomalous retinal correspondence unresponsive to orthoptic treatment. After perfect orthophoria for far