vergence

A disjunctive movement of the eyes in which the fixation axes are not parallel, as in convergence or divergence. [L. vergo, to incline, to turn]

- v. of lens the reciprocal of the principal focal distance used as a measure of the divergence or convergence of parallel rays.

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ver·gence 'vər-jən(t)s n a movement of one eye in relation to the other

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ver·gence (vurґjəns) [L. vergere to bend] 1. the amount of convergence or divergence of a pencil of rays entering or leaving a lens or mirror, expressed as the reciprocal of the distance from the lens or mirror to the focus of the rays. For rays through a principal focus, the vergence is equal to the focal power of the lens or mirror. See convergence (def. 2) and divergence (def. 1). 2. a disjunctive reciprocal rotation of both eyes around their horizontal, vertical, or anteroposterior axes such that the axes of fixation are not parallel. The kind of vergence is indicated by a prefix. See convergence (def. 3), divergence (def. 2), infravergence, supravergence, and see duction and version (def. 5).