Significance. Strabismus - misalignment of the visual axes - affects some 3% of the population and is a significant cause of visual disturbances such as diplopia, amblyopia, and stereoblindness. Definitive therapy for strabismus is usually surgical. Nevertheless, accuracy of surgical treatment remains disappointingly low: 20-50% of cases require multiple surgeries, exposing patients to additional morbidity and expense. A quantitative understanding of the mechanics of extraocular muscles and orbital connective tissues would improve diagnosis and treatment planning, and yet has been elusive. Such an understanding would also facilitate basic research on central or innervational causes of strabismus by allowing mechanical components to be isolated.
Aims and Methods. We propose to study the functional anatomy of orbital connective tissues and extraocular muscles in humans and monkeys. We will determine population norms for size and contractility of extraocular muscles in a diverse sample of humans, using magnetic resonance imaging (MRI). Similarly, we will characterize the pathophysiology of selected strabismic patients, focusing on superior oblique and lateral rectus disorders, and the time courses of their resolution. We will characterize orbital connective tissues by dissecting and serially-sectioning human and monkey cadavers, correlating human data with orbital MRI data. In fresh cadavers, we will measure the stiffness of Tenon's fascia and its sleeves, these constituting putative """"""""pulleys"""""""" of the rectus muscles. Using histochemical, immunohistochemical, and dye techniques, we will then discover the types and distribution of connective tissues and smooth muscles responsible for mechanical properties measured, as well as smooth muscle innervation. We will image regional stretching of Tenon's fascia as a function of gaze, using radio-opaque markers implanted in trained monkeys. In monkeys we will surgically modify Tenon's sleeves to evaluate mechanical effects and explore avenues for therapeutic enhancement of transposition surgery. We will unify and interpret all findings using the """"""""SQUINT"""""""" biomechanical model of binocular alignment, a system of equations describing static equilibrium of the globes and orbital tissues, implemented as a computer program. We will develop and prospectively test SQUINT using extensive pre- and post-operative Hess test binocular alignment data, saccadic measurements, and MRI data, collected specifically for this purpose. We will apply the model to study effects on alignment of post-surgical healing, using it in conjunction with post- surgical data, to infer orbital and innervational changes.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY008313-07
Application #
2019733
Study Section
Visual Sciences B Study Section (VISB)
Project Start
1991-01-06
Project End
1997-12-31
Budget Start
1997-01-01
Budget End
1997-12-31
Support Year
7
Fiscal Year
1997
Total Cost
Indirect Cost
Name
University of California Los Angeles
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
119132785
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
Chaudhuri, Zia; Demer, Joseph L (2018) Long-term Surgical Outcomes in the Sagging Eye Syndrome. Strabismus 26:6-10
Demer, Joseph L (2018) Knobby Eye Syndrome. Strabismus 26:33-41
Clark, Robert A; Demer, Joseph L (2018) The Globe's Eccentric Rotational Axis: Why Medial Rectus Surgery Is More Potent than Lateral Rectus Surgery. Ophthalmology 125:1234-1238
Shin, Andrew; Park, Joseph; Demer, Joseph L (2018) Opto-mechanical characterization of sclera by polarization sensitive optical coherence tomography. J Biomech 72:173-179
Rajab, Ghada Z; Suh, Soh Youn; Demer, Joseph L (2017) Magnetic resonance imaging in dissociated strabismus complex demonstrates generalized hypertrophy of rectus extraocular muscles. J AAPOS 21:205-209
Chang, Melinda Y; Shin, Andrew; Park, Joseph et al. (2017) Deformation of Optic Nerve Head and Peripapillary Tissues by Horizontal Duction. Am J Ophthalmol 174:85-94
Chang, Melinda Y; Demer, Joseph L; Isenberg, Sherwin J et al. (2017) Decreased Binocular Summation in Strabismic Amblyopes and Effect of Strabismus Surgery. Strabismus 25:73-80
Demer, Joseph L; Clark, Robert A; Suh, Soh Youn et al. (2017) Magnetic Resonance Imaging of Optic Nerve Traction During Adduction in Primary Open-Angle Glaucoma With Normal Intraocular Pressure. Invest Ophthalmol Vis Sci 58:4114-4125
Chang, Melinda Y; Coleman, Anne L; Tseng, Victoria L et al. (2017) Surgical interventions for vertical strabismus in superior oblique palsy. Cochrane Database Syst Rev 11:CD012447
Shin, Andrew; Yoo, Lawrence; Park, Joseph et al. (2017) Finite Element Biomechanics of Optic Nerve Sheath Traction in Adduction. J Biomech Eng 139:

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