Recent advances clarifying the etiologies of strabismus.
BACKGROUND
Strabismus is commonly encountered in neuro-ophthalmology practice. Adult patients may present with symptoms including disabling diplopia and decreased quality of life. Although presentation to the neuro-ophthalmologist often prompts a thorough workup for a neurologic basis of ocular misalignment, advances in orbital imaging and understanding of orbital mechanics have revealed novel mechanical causes. A goal of this review is to clarify mechanical mechanisms of strabismus that were formerly assumed be neurologic in origin.


METHODS
The authors combine their own research and clinical experience with a literature review using PubMed.


RESULTS
Aberrant paths of the extraocular muscles can lead to strabismus. The extraocular muscles have connective tissue pulleys that control muscle paths and are, in turn, influenced by the extraocular muscle orbital layers. Orbital connective tissues, including the pulleys, constrain extraocular muscle paths. Abnormalities of these tissues may lead to strabismus that is not due to neurologic pathology. Some extraocular muscles are divided into independent neuromuscular compartments, so that partial motor nerve lesions may manifest as selective denervation of only 1 compartment, complicating the presentation of neuropathic strabismus.


CONCLUSIONS
Strabismus in adults due to nonneurologic causes can result from recently described abnormalities of the orbital connective tissue pulley system. Advances in understanding of compartmental extraocular muscle anatomy and innervation can explain cyclovertical strabismus in partial nerve palsies. Recognition of the underlying pathogenesis of the strabismus can lead to improved treatments.
Department of Ophthalmology (JHP), Emory University, Atlanta, Georgia; Department of Pediatrics (JHP), Emory University, Atlanta, Georgia; Department of Ophthalmology (SLP, JLD), Stein Eye Institute, University of California, Los Angeles, California; Department of Neurology (JLD), University of California, Los Angeles, California; Neuroscience Interdepartmental Program (JLD), University of California, Los Angeles, California; and Bioengineering Interdepartmental Program (JLD), University of California, Los Angeles, California.
Jason H
JH
Peragallo
Stacy L
SL
Pineles
Joseph L
JL
Demer
D006801:Humans; D008279:Magnetic Resonance Imaging; D013285:Strabismus / Q000145:classification* / Q000209:etiology*