Editing Strabismus (section)

=== Direction and latency ===
Horizontal deviations are classified into two varieties, using prefixes: [[Esotropia|''eso-'']] describes inward or convergent deviations towards the midline, while ''exo-'' describes outward or divergent misalignment. Vertical deviations are also classified into two varieties, using prefixes: [[Hypertropia|''hyper-'']] is the term for an eye whose gaze is directed higher than the fellow eye, while ''hypo-'' refers to an eye whose gaze is directed lower. Finally, the prefix [[Cyclotropia|''cyclo-'']] refers to torsional strabismus, which occurs when the eyes rotate around the anterior–posterior axis to become misaligned and is quite rare.

These five directional prefixes are combined with ''-tropia'' (if manifest) or ''-phoria'' (if latent) to describe various types of strabismus. For example, a constant left hypertropia exists when a person's left eye is always aimed higher than the right. A person with an intermittent right esotropia has a right eye that occasionally drifts toward the person's nose, but at other times is able to align with the gaze of the left eye. A person with a mild exophoria can maintain fusion during normal circumstances, but when the system is disrupted, the relaxed posture of the eyes is slightly divergent.