Several methods of classifying ocular alignment and motility disorders are used, as no classification is perfect or all-inclusive. Terms used in these classifications are presented herein.
Age at onset
A deviation documented at or before age 6 months, presumably related to a defect present at birth. The term congenital is sometimes used, although it may be less accurate because the deviation is usually not present at birth.
A deviation with onset after 6 months of age, following a period of presumably normal ocular alignment.
A strabismus that is in the direction opposite that of a previous strabismus. For example, consecutive exotropia is an exotropia that follows an esotropia.
Dissociated strabismus complex
Consists of dissociated vertical deviation, dissociated horizontal deviation, and dissociated torsional deviation. The number of components varies, with some patients having all 3 and others having only 1. Dissociated vertical deviation is the most prevalent of the 3 components. The complex can be bilateral or unilateral; if it is bilateral, the degree of control of the deviation can vary between the eyes.
Overelevation in adduction and overdepression in adduction
These motility anomalies—frequently also called inferior oblique overaction and superior oblique overaction, respectively—can be caused by overaction of the oblique muscles, as well as by other mechanisms (see Chapter 11).
Underelevation in adduction and underdepression in adduction
These motility anomalies—frequently also called inferior oblique underaction and superior oblique underaction, respectively—can be caused by underaction of the oblique muscles, as well as by other mechanisms (see Chapter 11).
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.