Prefixes and Suffixes
A detailed nomenclature has evolved to describe the various types of ocular deviations. In this vocabulary, the prefix used indicates the relative position of the visual axes of the 2 eyes, or the direction of deviation.
Eso- The eye is rotated so that it is deviated nasally. Because the visual axes align at a point closer than the fixation target, this state is also known as convergent strabismus, one type of horizontal strabismus.
Exo- The eye is rotated so that it is deviated temporally. Because the visual axes are diverging from the fixation target, this state is also known as divergent strabismus, another form of horizontal strabismus.
Hyper- The eye is rotated so that it is deviated superiorly. This describes one type of vertical strabismus.
Hypo- The eye is rotated so that it is deviated inferiorly. This describes another type of vertical strabismus.
Incyclo- The eye is rotated so that the superior pole of the vertical meridian is rotated nasally. This state is known as intorsion.
Excyclo- The eye is rotated so that the superior pole of the vertical meridian is rotated temporally. This state is known as extorsion.
-phoria A latent deviation (eg, esophoria, exophoria, right hyperphoria); the deviation is controlled by the fusional mechanism so that the eyes remain aligned under binocular conditions.
-tropia A manifest deviation (eg, esotropia, exotropia, right hypertropia); the deviation exceeds the control of the fusional mechanism so that the eyes are misaligned under binocular conditions. Heterotropias can be constant or intermittent.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.