Adaptation to tilting of the visual environment in cyclotropia.

We evaluated adaptations to tilting of the visual environment in 18 patients with cyclotropia by comparison of subjective tests for torsion with the actual rotation of the globes determined by fundus photography. Patients with congenital cyclotropia had a sensory reorientation of the spatial values of retinal meridians in the cyclotropic eye that prevented awareness of tilting of the environment under uniocular and binocular conditions. Patients with cyclotropia acquired as adults in many instances also had retinal sensory reorientations of the cyclotropic eye or eyes. Additionally, they used spatial clues from the visual environment to correct for image tilting under uniocular conditions. Under dissociated binocular conditions, however, these patients became aware of tilting of the visual environment, and therefore these adaptations were less deeply rooted than those in patients with congenital cyclotropia. Because certain patients with acquired cyclotropia showed evidence of using these adaptations under uniocular conditions but had constant or intermittent torsional diplopia under casual binocular viewing conditions, binocular mechanisms such as cyclofusion, suppression, and anomalous retinal correspondence may also be necessary to eliminate subjective tilting of the visual environment.