Area of Binocuilar Vision in Anomalous Retinal Correspondence*

SEVERAL authors (Lyle and Foley, 1955; Naylor, Shannon, and Stanworth, 1956; Naylor and Stanworth, 1959; Guzzinati and Salvi, 1957; Pasino, Maraini, and Santori, 1963) have observed the absence of a stereoscopic perception of depth in early convergent strabismus with anomalous retinal correspondence. Even in patients with an extremely small fixed ocular deviation and harmonious anomalous retinal correspondence (h.a.r.c.), the stereoscopic visual acuity is not significantly different from that of subjects with deep uniocular amblyopia (Pasino and others, 1963). The interpretation of these observations is by no means certain, considering that the sensory condition of these patients permitted a subnormal biretinal cooperation with a certain range of fusional amplitude; the latter was shown to be almost exclusively based on variations of the angle of anomaly rather than on true fusional movements (Hallden, 1952; Pasino and Maraini, 1964; Maraini and Pasino, 1964). Comparing sensory fusion in normal and anomalous binocular vision, Hallden (1952) pointed out that sensory fusion in anomalous correspondence is neither confined within such narrow limits nor characterized by the occurrence of stereo-effects. According to Hallden (1952), a large amplitude of sensory fusion could not be expected to occur without a loss of stereopsis. In the present investigation an attempt has been made to evaluate the amplitude of sensory fusion and therefore the range of binocular vision in patients with fixed small-angle early convergent strabismus with h.a.r.c. and in a few patients of this kind in whom orthophoria had been attained (by means of surgery and of prisms) together with a normal binocular localization in free space. As far as we know this subject has not been discussed in the literature.