Most of what we know about treating occasional squinters with anomalous correspondence comes from experience with exotropes where this combination of conditions is fairly common. Nonetheless, the treatment principles apply to the rarely found occasional esotropes with anomalous correspondence. When treating occasional esotropia with anomalous correspondence it is important to recall that when these patients are not squinting (fusing) they have normal retinal correspondence (zero angle of anomaly). The anomalous correspondence that manifests itself when the strabismus is present becomes normal as fusional vergence is exercised to straighten the eyes. This "co-variation" between fusional vergence and the angle of anomaly (Hallden, 1952) forms the basis for treating this type of strabismus. Specifically, treatment is directed at enhancing the already-present fusional vergence which allows the squint and the anomalous correspondence to be overcome simultaneously.
Correcting the hyperopic refractive error of the occasional esotrope with ARC produces results much like that for occasional squinters with normal correspondence, that is correcting seemingly trivial refractive errors produces substantial increases in the frequency of fusion. Added plus lenses for near are useful for some of these patients but they do not produce the straight-forward results that occur in occasional squinters with normal correspondence. Added lenses change accommodative vergence, but this vergence never or rarely (Kerr, 19__; Daum, 198_) produces associated changes in the angle of anomaly. When added plus lenses, for example, are applied clinically to occasional esotropes with anomalous correspondence, small amounts seem to facilitate fusional vergence and enhance bifixation with correspondence becoming normal. Cavalier use of added lenses for occasional esotropes with anomalous correspondence should be avoided, and judicious use should be encouraged.
As with added lenses, horizontal prisms can be troublesome for occasional squinters with anomalous correspondence. Giving base-out prisms to an intermittent esotrope with anomalous correspondence, for example, will probably result in the eyes converging to the prisms in order for the retinal images to continue to fall on (anomalously) corresponding retinal points. However, prisms do need to be considered early in treating these patients; principally to neutralize an existing vertical deviation that may be impairing fusion. Usually, but not always, anomalous correspondence does not seem to be present vertically in occasional squinters; thus, vertical prisms are effective in neutralizing a vertical deviation and enhancing fusion in these patients
Since occasional strabismics usually do not have much amblyopia, treatment of the amblyopia can usually be accomplished with occasional occlusion. This passive treatment can be facilitated by anti-suppression training --- but there is typically little if any suppression coexisting with the anomalous correspondence. Anti-suppression orthoptics for these patients is usually needed only to break down small areas of central suppression, but not to create diplopia (when the eyes deviate) as a stimulus to fusion as is done for occasional squinters with normal correspondence.
As pointed out earlier, motor fusion training gets the eyes straight and when accomplished, correspondence becomes normal. The challenge is how to train fusional vergence when diplopia cannot be used as a stimulus for fusional vergence when the eyes are deviated --- since the anomalous correspondence with the eyes deviated prevents diplopia. Occasional esotropes with anomalous correspondence can be trained to sense when the eye deviates and to straighten the eye by executing a reflex fusional vergence movement. Training facility of fusional vergence and the sensory aspects of fusion (such as stereopsis) helps these patients develop the necessary reflex fusional vergence.
Surgery for these patients is not usually necessary unless the angle of deviations is large or there is discomfort. Correspondence can change postsurgically quickly and in ways unassociated with covariation. Thus, prompt evaluation of the postsurgical status can help in determining the need for additional surgical management (including adjusting the original suture) or in giving postsurgical vision training or optics..