Disjunctive Optokinetic Nystagmus in a Naturally Esotropic Macaque Monkey: Interaction between Nasotemporal Asymmetries of Versional Eye Movement and Convergence

Yıldırım, Cem; Tychsen, Lawrence

doi:10.1159/000055609

Cited by 9 publications

(4 citation statements)

References 20 publications

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“…16,22–24 and in strabismic monkeys. 25–26 Additionally, we also observed that the latency of DVR was elongated when scotomas were large. It has been demonstrated that the latency was usually longer when stimuli were small, 17, 27–31 when peripheral disparities were used, 17 and in strabismic patients with anomalous correspondence.…”

Section: Discussionsupporting

confidence: 56%

Effect of Artificial Scotomas on Open-Loop Disparity Vergence Eye Movements

Yang

Hertle

Zhu

et al. 2015

Optometry and Vision Science

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Purpose To investigate the effect of an artificial scotoma on open-loop disparity vergence responses and vergence control mechanisms, we examined open-loop disparity vergence responses to disparity stimuli using monocular artificial scotomas in normal subjects. Methods Using a mirror haploscope with two computer monitors, we delivered disparity stimuli on a pair of random dot patterns subtending 40×30 degrees at 47 cm from each eye. The scotomas were black circles located in the center of a random dot pattern for the left eye. Eye movements of both eyes were recorded with a magnetic search coil system. Results We first found that the amplitudes of disparity vergence responses were gradually decreased and the latency of disparity vergence responses were moderately increased as the size of the scotomas was increased. Secondly, monocular responses from each eye were symmetrical although the stimuli to each eye were asymmetrical. Conclusions The results suggest that the monocular eye movements in disparity vergence are controlled by a binocular central mechanism, not driven separately by monocular inputs in the open-loop window.

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Section: Discussionsupporting

confidence: 56%

Effect of Artificial Scotomas on Open-Loop Disparity Vergence Eye Movements

Yang

Hertle

Zhu

et al. 2015

Optometry and Vision Science

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“…9 The simian model has thus been used to understand the etiology, consequences, and treatments of human strabismus. 23,24,[33][34][35][36][37] In the current study, we investigated orbital anatomy in monkeys with natural or artificial strabismus, comparing findings with those in orthotropic animals. Because cadaveric MRI does not distinguish tendons and connective tissue in the most anterior orbit, histologic examination of whole orbits was also performed.…”

Section: Discussionmentioning

confidence: 99%

Horizontal Rectus Muscle Anatomy in Naturally and Artificially Strabismic Monkeys

Narasimhan

Tychsen

Poukens³

et al. 2007

Invest. Ophthalmol. Vis. Sci.

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Purpose-Structural abnormalities of extraocular muscles (EOMs) or their pulleys are associated with some forms of human strabismus. This experiment was conducted to investigate whether such abnormalities are associated with artificial or naturally occurring strabismus in monkeys.Methods-Binocular alignment and grating visual acuities were determined in 10 monkeys representing various species using search coil recording and direct observations. Four animals were orthotropic, two had naturally occurring "A"-pattern esotropia, two had concomitant and one had "V"-pattern esotropia artificially induced by alternating or unilateral occlusion in infancy, and one had "A"-pattern exotropia artificially induced by prism wear. After euthanasia, 16 orbits were examined by high-resolution magnetic resonance imaging (MRI) in the quasicoronal plane. Paths and sizes of horizontal rectus EOMs were analyzed quantitatively in a standardized coordinate system. Whole orbits were then serially sectioned en bloc in the quasicoronal plane, stained for connective tissue, and compared with MRI. Nerve and EOM features were analyzed quantitatively.Results-Quantitative analysis of MRI revealed no significant differences in horizontal rectus EOM sizes or paths among orthotropic or naturally or artificially strabismic monkeys. Histologic examination demonstrated no differences in EOM size, structure, or innervation among the three groups, and no differences in connective tissues in the pulley system. The accessory lateral rectus (ALR) EOM was present in all specimens, but was small, inconsistently located, and sparsely innervated. Characteristics of the ALR did not correlate with strabismus.Conclusions-Major structural abnormalities of horizontal rectus EOMs and associated pulleys are unrelated to natural or artificial horizontal strabismus in the monkeys studied. The ALR is unlikely to contribute to horizontal strabismus in primates. However, these findings do not exclude a possible role of pulley abnormalities in disorders such as cyclovertical strabismus.Before the development of quantitative models of extraocular biomechanics, 1-3 it was believed sufficient to describe orbital anatomy by cadaveric measurements of extraocular It has subsequently emerged that the rectus and inferior oblique EOMs of humans and monkeys do indeed have highly structured soft pulleys that regulate EOM pulling directions. 7-10 The pulleys act as functional origins of the rectus EOMs. 11 Rectus EOMs travel through their respective pulleys, which imply that the pulleys must lie along the EOM paths. Many cases of human incomitant cyclovertical strabismus are associated with displacement of one or more rectus EOM pulleys. "A" and "V" patterns of incomitance in strabismic patients consistently match those predicted by computational simulation based on measured pulley locations, suggesting that pulley heterotopy caused the strabismus. 12,13 Extreme pulley heterotopy is associated with esotropia and hypotropia in axial high myopia, the "heavy-eye syndrome." 14-1...

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“…6,7,30,31 Infant NHPs with strabismus display the same constellation of perceptual and ocular motor abnormalities found in strabismic humans, including defective stereopsis, abnormal vergence, and horizontal OKN asymmetries. 14,16,18,[32][33][34][35] It is unclear, however, what effect strabismus has on vertical OKN, or the interaction between horizontal and vertical OKN in NHPs.…”

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confidence: 99%