Do you really need your oblique muscles? Adaptations and exaptations.

Full Abstract

BACKGROUND:
Primitive adaptations in lateral-eyed animals have programmed the oblique muscles to counterrotate the eyes during pitch and roll. In humans, these torsional movements are rudimentary.

PURPOSE:
To determine whether the human oblique muscles are vestigial.

METHODS:
Review of primitive oblique muscle adaptations and exaptations in human binocular vision.

RESULTS:
Primitive adaptations in human oblique muscle function produce rudimentary torsional eye movements that can be measured as cycloversion and cyclovergence under experimental conditions. The human torsional regulatory system suppresses these primitive adaptations and exaptively modulates cyclovergence to facilitate stereoscopic perception in the pitch plane. It also recruits the oblique muscles to generate cycloversional saccades that preset torsional eye position immediately preceding volitional head tilt, permitting instantaneous nonstereoscopic tilt perception in the roll plane.

CONCLUSIONS:
The evolution of frontal binocular vision has exapted the human oblique muscles for stereoscopic detection of slant in the pitch plane and nonstereoscopic detection of tilt in the roll plane. These exaptations do not erase more primitive adaptations, which can resurface when congenital strabismus and neurologic disease produce evolutionary reversion from exaptation to adaptation.

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Author information

Author/s: Brodsky, Michael C (MC);

Affiliation: Department of Ophthalmology, University of Arkansas for Medical Sciences, Little Rock, USA.

Journal and publication information

Publication Type: Journal Article

Journal: Archives of ophthalmology (Arch Ophthalmol), published in United States. (Language: eng)

Reference: 2002-Jun; vol 120 (issue 6) : pp 820-8

Dates: Created 2002/06/06; Completed 2002/06/17; Revised 2005/09/22;

PMID: 12049590, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

Comments and Corrections

CommentIn: Arch Ophthalmol. 2005 Sep;123(9):1281; author reply 1281. (PMID: 16157820)

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adaptation, Ocular - physiology
Eye Movements - physiology
Humans

Oculomotor Muscles - physiology
Vision, Binocular - physiology
Visual Perception - physiology

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