heterophoria


heterophoria

 [het″er-o-for´e-ah] failure of the visual axes to remain parallel after the visual fusional stimuli have been eliminated. The various forms of heterophoria are spoken of as phorias, their direction being indicated by the appropriate prefix, as cyclophoria, esophoria, exophoria, hyperphoria, and hypophoria. adj., adj heterophor´ic.

het·er·o·pho·ri·a

(het'ĕr-ō-fō'rē-ă), A tendency for deviation of the eyes from parallelism, prevented by binocular vision. [hetero- + G. phora, movement]

latent squint

Deviation of an eye from the visual axis that occurs by covering one or more eyes. With both eyes open, the visual axes are aligned. When one eye is covered, it deviates. Minimal heterophoria is present in most people and asymptomatic. Small latent divergent squints are common in children up to age 5 and, because they’re not associated with adverse effects, don’t require intervention. Small latent convergent squints are often accompanied by hypermetropia, for which corrective lenses are prescribed to prevent squint progression.

het·er·o·pho·ri·a

(het'ĕr-ō-fōr'ē-ă) A tendency for deviation of the eyes from parallelism, prevented by binocular vision. [hetero- + G. phora, movement]

heterophoria

The tendency for the two visual axes of the eyes not to be directed towards the point of fixation, in the absence of an adequate stimulus to fusion. Thus, the active and passive positions do not coincide for that particular fixation distance. This tendency is characterized by a deviation that can take various forms according to its relative direction such as esophoria, exophoria, excyclophoria, incyclophoria, hyperphoria, hypophoria. Syn. phoria. See anisophoria; dextrophoria; dissociation; kataphoria; laevophoria.
associated heterophoria A term sometimes used to denote the prism power necessary to align the nonius markers of a fixation disparity test. It is not strictly speaking a heterophoria because only part of the visual field is dissociated while the rest of the field is fused (that fused area is often referred to as fusion lock or binocular lock). The dissociation of only part of the field is achieved by using either a method of cross-polarization (e.g. Mallet fixation disparity unit) or a septum (e.g. Turville infinity balance test). Syn. aligning prism; compensating prism. See retinal disparity; Disparometer; Mallett fixation disparity unit; Turville infinity balance test.
compensated heterophoria Any heterophoria that does not give rise to symptoms or to suppression.
decompensated d. See uncompensated heterophoria.
dissociated heterophoria Any heterophoria which is revealed by methods which produce complete dissociation such as the cover test, the Maddox rod test, the Thorington test, the von Graefe's test, the diplopia test, etc.
uncompensated heterophoria Any heterophoria which gives rise to symptoms or to suppression. The symptoms are associated with visual tasks, especially close work, but also occasionally, inadequate illumination. Resting the eyes will usually lessen the symptoms. Unbalanced spectacle correction, deterioration in the patient's general health, worry and anxiety can also sometimes give rise to an uncompensated heterophoria. This type of heterophoria is presumed to manifest itself as fixation disparity. Syn. decompensated heterophoria. See Disparometer; Mallett fixation disparity unit; relieving prism.