V-Pattern Esotropia and Exotropia
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Duane first described V-pattern strabismus in 1897. [1] Other investigators also studied these phenomena, contributing to the understanding of them. Costenbader and colleagues recommended measuring the horizontal deviations in upgaze and downgaze as part of all routine motility examinations. [2]
Two types of V-patterns can occur, as shown in the images below.
V-pattern exotropia is an exodeviation with greater exotropia in upgaze than in downgaze.
V-pattern esotropia is an esodeviation with greater esotropia in downgaze than in upgaze.
Comitant horizontal deviations are those in which the angle of deviation is the same in all gaze positions. Incomitant horizontal deviations are those in which the angle of deviation varies in different gaze positions. Horizontal deviations may have lateral incomitances and vertical incomitances. In lateral incomitances, significant differences exist in the amount of horizontal deviation in primary gaze versus side gaze, whereas, in vertical incomitances, significant differences exist in the amount of horizontal deviation in upgaze versus downgaze.
When the eyes diverge more than 10 prism diopters (PD) from upgaze to downgaze, an A-pattern is present; when the eyes converge more than 15 PD from upgaze to downgaze, a V-pattern is present.
Other types of vertical incomitances, which are less common, include X, Y, and lambda patterns. This discussion is limited to V-pattern strabismus.
Multiple factors may be responsible for V-pattern strabismus, and, in a given individual, one or more factors may contribute toward its cause.
The most widely accepted mechanism contributing to the causation of V-pattern strabismus is associated with inferior oblique muscle overaction and/or relative underaction of the superior oblique muscles, as shown in the images below.
Inferior oblique muscle overaction produces significant horizontal deviation in upgaze. In upgaze, the horizontal action of the inferior oblique muscles is abduction; therefore, inferior oblique muscle overaction produces relative divergence in elevation. A V-pattern results in greater exotropia (or less esotropia) in upgaze and greater esotropia (or less exotropia) in downgaze. Not all V-pattern strabismus is associated with oblique muscle dysfunction.
An association exists between individuals with hypoplasia of the malar bones, anti-Mongoloid lid slants, and S-shaped contours of the lower lid, and overaction of the inferior oblique muscles and V-pattern strabismus. Patients with craniosynostosis have shallow orbits, and the angle between the visual axis and the insertion of the inferior oblique muscle is increased. This increased angle increases the abduction ability of the inferior oblique muscles in upgaze, resulting in a V-pattern. Contributing to this condition is the complex interplay of these factors with excyclotorsion of the globe.
Upward displacement of the pulley systems around the lateral rectus muscle may cause V-pattern strabismus.
Initially, this theory was believed to be responsible for V-pattern strabismus, but no convincing evidence supports it. In V-pattern esotropia, the medial rectus muscle was believed to overact, thereby increasing esotropia in downgaze, and, in V-pattern exotropia, the lateral rectus muscle overaction was responsible for increased exotropia in upgaze.
One theory states that V-pattern strabismus occurs because of underacting superior recti muscles and corresponding overacting inferior oblique muscles. This hypothesis was applied when nasal and temporal displacements were used to treat A- and V-patterns. This theory has been abandoned.
Alterations of the angle of the insertion of the oblique muscle with the visual axis can reduce cyclorotation and abduction forces and increase the vertical function of the oblique muscle.
Among the suggested causes of V-pattern strabismus are anomalies of the horizontal rectus scleral insertions. They may be inserted above or below the usual positions.
V-patterns are acquired after superior oblique muscle palsy and are a prominent feature of bilateral superior oblique muscle palsies.
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Although the exact prevalence of V-pattern strabismus in a given population is not known, 12.5-50% of patients with horizontal strabismus have an associated A- or V-pattern. V-pattern esotropia is not as commonly seen as V-pattern exotropia.
Patients may experience diplopia that affects their everyday activities, such as driving and reading. In addition, the inability of patients to fuse in different gaze positions can interfere with other activities, including sports and recreation. The cosmetic appearance of V-pattern strabismus coupled with its social implications may be bothersome to patients. Over time, the associated anomalous head position could lead to secondary neck pain and similar problems.
No racial predilection exists.
No sexual predilection exists.
No age predilection exists.
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Neepa Thacker, MBBS, MS, DNB, FRCS Consulting Staff, Department of Pediatric Ophthalmology and Strabismus, Breach Candy Hospital; Head, Department of Pediatric Ophthalmology and Strabismus, Lotus Eye Hospital, India
Disclosure: Nothing to disclose.
Arthur L Rosenbaum, MD
Arthur L Rosenbaum, MD is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, American Medical Association
Disclosure: Nothing to disclose.
Federico G Velez, MD Assistant Clinical Professor, Department of Ophthalmology, Division of Pediatric Ophthalmology and Strabismus, Jules Stein Eye Institute, University of California, Los Angeles, David Geffen School of Medicine
Federico G Velez, MD is a member of the following medical societies: American Academy of Ophthalmology, American Association for Pediatric Ophthalmology and Strabismus, Association for Research in Vision and Ophthalmology
Disclosure: Nothing to disclose.
Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Received salary from Medscape for employment. for: Medscape.
J James Rowsey, MD Former Director of Corneal Services, St Luke’s Cataract and Laser Institute
J James Rowsey, MD is a member of the following medical societies: American Academy of Ophthalmology, American Association for the Advancement of Science, American Medical Association, Association for Research in Vision and Ophthalmology, Florida Medical Association, Sigma Xi, Southern Medical Association, Pan-American Association of Ophthalmology
Disclosure: Nothing to disclose.
Hampton Roy, Sr, MD Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences
Hampton Roy, Sr, MD is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, Pan-American Association of Ophthalmology
Disclosure: Nothing to disclose.
Michael J Bartiss, OD, MD Medical Director, Ophthalmology, Family Eye Care of the Carolinas and Surgery Center of Pinehurst
Michael J Bartiss, OD, MD is a member of the following medical societies: American Academy of Ophthalmology, North Carolina Medical Society, American Academy of Pediatrics, American Association for Pediatric Ophthalmology and Strabismus
Disclosure: Nothing to disclose.
V-Pattern Esotropia and Exotropia
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