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. Whether the cause is central or orbital, definitive therapy for strabismus is usually surgical. Nevertheless, accuracy of surgical treatment remains disappointingly low: 20-50% of cases require multiple surgeries, each exposing patients to additional morbidity and expense. A validated computational model of ocular static mechanics would improve diagnosis and treatment planning, and yet has been elusive, due to absence of a concerted clinical-basic science collaboration devoted to its development. Such a model would also facilitate basic research on central or innervational causes of strabismus by allowing isolation of mechanical components of disease states, surgical manipulations, and healing processes.
Aims and Methods. The """"""""SQUINT"""""""" computational biomechanical model of binocular alignment is a system of equations describing static equilibrium of the globes and orbital tissues, implemented as a computer program. We propose to develop, test, and apply the SQUINT model. Development of the model will include (a) eliminating the existing assumptions regarding reciprocal innervation by implementing globe translation force-balance constraints, and (b) incorporating a novel treatment of the previously-neglected role of orbital connective tissues, suggested by our previous 3-dimensional magnetic resonance imaging (MRI) studies of functional relationships of extra-ocular muscle paths to the globe. We will seek further evidence for connective tissue """"""""pulleys"""""""", with new MRI studies of patients with conditions in which muscles abnormally strain connective tissues: varieties of Duane's retraction syndrome, and muscle transposition surgery performed with different surgical techniques. These studies will permit non-invasive, quantitative determination of mechanical properties of previously-inaccessible connective tissues. We will develop and prospectively test the model using extensive pre- and post-operative Hess test binocular alignment data, saccadic trajectory measurements, intra-operative mechanical measurements, and MRI data, collected specifically for this purpose. We will apply the model to study the effects on alignment of post-surgical healing, using it in conjunction with longitudinal post-surgical data, to infer orbital and innervational changes.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
Project #
Application #
Study Section
Visual Sciences B Study Section (VISB)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of California Los Angeles
Schools of Medicine
Los Angeles
United States
Zip Code
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
Chaudhuri, Zia; Demer, Joseph L (2018) Long-term Surgical Outcomes in the Sagging Eye Syndrome. Strabismus 26:6-10
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:

Showing the most recent 10 out of 179 publications