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Sangoi A, Scheiman M, Yaramothu C, Santos EM, Gohel S, Alvarez TL. Convergence Insufficiency Neuro-Mechanism Adult Population Study: Phoria Adaptation Results. Invest Ophthalmol Vis Sci 2021; 62:19. [PMID: 34406329 PMCID: PMC8374988 DOI: 10.1167/iovs.62.10.19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The purpose of this study was to compare changes in phoria adaptation between young adult binocularly normal controls (BNCs) and participants with symptomatic convergence insufficiency (CI), who were randomized to either office-based vergence accommodative therapy (OBVAT) or office-based placebo therapy (OBPT). Methods In the double-masked randomized clinical trial, 50 BNC and 50 CI participants were randomized to the following therapeutic interventions: OBVAT or OBPT with home reinforcement for 12 one-hour office sessions. A 6∆ base-out and 6∆ base-in phoria adaptation experiment at near (40 cm) was conducted using the flashed Maddox rod technique at baseline and at outcome. Measurements included the rate and the magnitude of phoria adaptation. Results At baseline, BNC and CI participants had significantly different rates and magnitudes of base-in and base-out phoria adaptation (P < 0.001). When comparing the outcome to baseline measurements, significant main effect differences in longitudinal measurements were observed for the magnitude and the rate of phoria adaptation for both base-out and base-in experiments (P < 0.05). For the magnitude and rate of phoria adaptation, post hoc analyses using paired t-tests revealed that the CI group administered the OBVAT intervention exhibited a significant increase in the magnitude and rate of phoria adaptation compared to baseline for both base-in and base-out phoria adaptation (P < 0.01) but not for those administered OBPT. Conclusions Phoria adaptation is significantly different at baseline between those with normal binocular vision and symptomatic CI participants. OBVAT significantly improves the rate and magnitude of both base-out and base-in phoria adaptation at near compared to OBPT. Results have clinical implications for new therapeutic interventions.
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Affiliation(s)
- Ayushi Sangoi
- Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States
| | - Mitchell Scheiman
- Pennsylvania College of Optometry, Salus University, Philadelphia, Pennsylvania, United States
| | - Chang Yaramothu
- Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States.,School of Applied Engineering and Technology, New Jersey Institute of Technology, Newark, New Jersey, United States
| | - Elio M Santos
- Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States
| | - Suril Gohel
- Department of Health Informatics, Rutgers University School of Health Professions, Newark, New Jersey, United States
| | - Tara L Alvarez
- Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States
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Brodsky MC. Phoria Adaptation: The Ghost in the Machine. J Binocul Vis Ocul Motil 2020; 70:1-10. [PMID: 31986106 DOI: 10.1080/2576117x.2019.1706699] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 12/16/2019] [Indexed: 06/10/2023]
Abstract
Importance: Phoria adaptation is a central tonus mechanism that provides plasticity to binocular alignment. However, its slow dissipation inevitably adulterates our clinical strabismus measurements.Purpose: To examine the role of phoria adaptation in normal binocular control, understand its neural substrate, and explore how it can alter our clinical measurements in common forms of strabismus.Methods: Investigation into the role of phoria adaptation in maintaining binocular alignment and its role in altering clinical strabismus measurement.Results: Phoria adaptation permeates all aspects of binocular alignment. It accounts for the stability of orthophoria, "latent" phorias, tenacious proximal fusion in intermittent exotropia, large fusional vertical amplitudes in congenital superior oblique muscle palsy, the "eating up" of prisms in accommodative esotropia, the smaller measured distance deviation in patients with high AC/A ratio or convergence excess, absence of physiologic skew deviation during head tilt, fusional divergence amplitudes, and spread of comitance. This binocular control system probably arises from a cerebellar learning mechanism that involves input via climbing fibers to the inferior olive, which provide a powerful timing and error signal to the cerebellar Purkinje cells to produce activity-dependent modification analogous to long-term potentiation.Conclusions: Phoria adaptation is generated by a central neural integrator that provides inertia, plasticity, and positional stability to human binocular vision.
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Affiliation(s)
- Michael C Brodsky
- Department of Ophthalmology and Neurology, Mayo Clinic, Rochester, Minnesota
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3
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A differential role for the posterior cerebellum in the adaptive control of convergence eye movements. Brain Stimul 2019; 13:215-228. [PMID: 31427273 DOI: 10.1016/j.brs.2019.07.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 06/15/2019] [Accepted: 07/26/2019] [Indexed: 11/21/2022] Open
Abstract
INTRODUCTION The vergence oculomotor system possesses two robust adaptive mechanisms; a fast "dynamic" and a slow "tonic" system that are both vital for single, clear and comfortable binocular vision. The neural substrates underlying these vergence adaptive mechanisms in humans is unclear. METHODS We investigated the role of the posterior cerebellum in convergence adaptation using inhibitory continuous theta-burst repetitive transcranial magnetic stimulation (cTBS) within a double-blind, sham controlled design while eye movements were recorded at 250hz via infrared oculography. RESULTS In a preliminary experiment we validated our stimulation protocols by reproducing results from previous work on saccadic adaptation during the classic double-step adaptive shortening paradigm. Following this, across a series of three separate experiments we observed a clear dissociation in the effect of cTBS on convergence adaptation. Dynamic adaptation was substantially reduced while tonic adaptation was unaffected. Baseline dynamic fusional vergence response were also unaffected by stimulation. CONCLUSIONS These results indicate a differential role for the posterior cerebellum in the adaptive control of convergence eye movements and provide initial evidence that repetitive transcranial magnetic stimulation is a viable tool to investigate the neurophysiology of vergence control. The results are discussed in the context of the current models of implicit motor adaptation of vergence and their application to clinical populations and technology design in virtual and augmented head mounted display architectures. SIGNIFICANCE STATEMENT The cerebellum plays a critical role in the adaptive control of motor systems. Vergence eye movements shift our gaze in depth allowing us to see in 3D and exhibit two distinct adaptive mechanisms that are engaged under a range of conditions including reading, wearing head-mounted displays and using a new spectacle prescription. It is unclear what role the cerebellum plays in these adaptive mechanisms. To answer this, we temporarily disrupted the function of the posterior cerebellum using non-invasive brain stimulation and report impairment of only one adaptive mechanism, providing evidence for neural compartmentalization. The results have implications for vergence control models and applications to comfort and experience studies in head-mounted displays and the rehabilitation of clinical populations exhibiting vergence dysfunctions.
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Kang SL, Shaikh AG, Ghasia FF. Vergence and Strabismus in Neurodegenerative Disorders. Front Neurol 2018; 9:299. [PMID: 29867716 PMCID: PMC5964131 DOI: 10.3389/fneur.2018.00299] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 04/18/2018] [Indexed: 01/03/2023] Open
Abstract
Maintaining proper eye alignment is necessary to generate a cohesive visual image. This involves the coordination of complex neural networks, which can become impaired by various neurodegenerative diseases. When the vergence system is affected, this can result in strabismus and disorienting diplopia. While previous studies have detailed the effect of these disorders on other eye movements, such as saccades, relatively little is known about strabismus. Here, we focus on the prevalence, clinical characteristics, and treatment of strabismus and disorders of vergence in Parkinson’s disease, spinocerebellar ataxia, Huntington disease, and multiple system atrophy. We find that vergence abnormalities may be more common in these disorders than previously thought. In Parkinson’s disease, the evidence suggests that strabismus is related to convergence insufficiency; however, it is responsive to dopamine replacement therapy and can, therefore, fluctuate with medication “on” and “off” periods throughout the day. Diplopia is also established as a side effect of deep brain stimulation and is thought to be related to stimulation of the subthalamic nucleus and extraocular motor nucleus among other structures. In regards to the spinocerebellar ataxias, oculomotor symptoms are common in many subtypes, but diplopia is most common in SCA3 also known as Machado–Joseph disease. Ophthalmoplegia and vergence insufficiency have both been implicated in strabismus in these patients, but cannot fully explain the properties of the strabismus, suggesting the involvement of other structures as well. Strabismus has not been reported as a common finding in Huntington disease or atypical parkinsonian syndromes and more studies are needed to determine how these disorders affect binocular alignment.
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Affiliation(s)
- Sarah L Kang
- Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Aasef G Shaikh
- Case Western Reserve University School of Medicine, Cleveland, OH, United States.,Daroff-Dell'Osso Ocular Motility Laboratory, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, United States
| | - Fatema F Ghasia
- Daroff-Dell'Osso Ocular Motility Laboratory, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, United States.,Cole Eye Institute, Cleveland Clinic, Cleveland, OH, United States
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Jung J, Klaehn L, Brodsky MC. Stability of human binocular alignment in the dark and under conditions of nonfixation. J AAPOS 2016; 20:353-7. [PMID: 27346855 DOI: 10.1016/j.jaapos.2016.05.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 05/26/2016] [Accepted: 05/31/2016] [Indexed: 11/15/2022]
Abstract
PURPOSE To evaluate the stability of human binocular alignment under conditions of altered fixation and luminance. METHODS Horizontal binocular alignment in 8 healthy orthotropic subjects was measured using infrared video-oculography (VOG) under conditions of binocular fixation and luminance change. Each testing condition was preceded by a binocular fixation period in room light (475 lux) to define the baseline binocular alignment. Binocular alignment was then measured in darkness without fixation, in room light through a semitranslucent filter that precluded fixation, and in darkness with a distant fixational target. We used the signed rank test to determine statistically whether these experimental conditions induced significant binocular alignment change from each baseline binocular alignment. RESULTS The mean horizontal binocular alignment in the dark without fixation was similar to baseline binocular alignment (0.2° ± 2.8°; P = 0.4). The mean horizontal binocular alignment without fixation in room light was also similar to baseline binocular alignment (-1.4° ± 1.6°; P = 0.08). The mean horizontal binocular alignment in the dark when a fixational target was provided showed an exodrift compared to baseline alignment (2.3° ± 1.0°; P = 0.0004). CONCLUSIONS The human brain does not require visual input to maintain binocular alignment on a short-term basis. The resilience of binocular alignment probably reflects the presence of phoria adaptation.
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Affiliation(s)
- Jaeho Jung
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota
| | - Lindsay Klaehn
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota
| | - Michael C Brodsky
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota; Department of Neurology, Mayo Clinic, Rochester, Minnesota.
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Brodsky MC, Jung J. Intermittent Exotropia and Accommodative Esotropia: Distinct Disorders or Two Ends of a Spectrum? Ophthalmology 2015. [PMID: 26210597 DOI: 10.1016/j.ophtha.2015.03.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Bohlen MO, Warren S, May PJ. A central mesencephalic reticular formation projection to the supraoculomotor area in macaque monkeys. Brain Struct Funct 2015; 221:2209-29. [PMID: 25859632 DOI: 10.1007/s00429-015-1039-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 04/02/2015] [Indexed: 11/26/2022]
Abstract
The central mesencephalic reticular formation is physiologically implicated in oculomotor function and anatomically interwoven with many parts of the oculomotor system's premotor circuitry. This study in Macaca fascicularis monkeys investigates the pattern of central mesencephalic reticular formation projections to the area in and around the extraocular motor nuclei, with special emphasis on the supraoculomotor area. It also examines the location of the cells responsible for this projection. Injections of biotinylated dextran amine were stereotaxically placed within the central mesencephalic reticular formation to anterogradely label axons and terminals. These revealed bilateral terminal fields in the supraoculomotor area. In addition, dense terminations were found in both the preganglionic Edinger-Westphal nuclei. The dense terminations just dorsal to the oculomotor nucleus overlap with the location of the C-group medial rectus motoneurons projecting to multiply innervated muscle fibers suggesting they may be targeted. Minor terminal fields were observed bilaterally within the borders of the oculomotor and abducens nuclei. Injections including the supraoculomotor area and oculomotor nucleus retrogradely labeled a tight band of neurons crossing the central third of the central mesencephalic reticular formation at all rostrocaudal levels, indicating a subregion of the nucleus provides this projection. Thus, these experiments reveal that a subregion of the central mesencephalic reticular formation may directly project to motoneurons in the oculomotor and abducens nuclei, as well as to preganglionic neurons controlling the tone of intraocular muscles. This pattern of projections suggests an as yet undetermined role in regulating the near triad.
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Affiliation(s)
- Martin O Bohlen
- Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS, 39216, USA
| | - Susan Warren
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS, 39216, USA
| | - Paul J May
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS, 39216, USA.
- Department of Ophthalmology, University of Mississippi Medical Center, Jackson, MS, 39216, USA.
- Department of Neurology, University of Mississippi Medical Center, Jackson, MS, 39216, USA.
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Das VE. Responses of cells in the midbrain near-response area in monkeys with strabismus. Invest Ophthalmol Vis Sci 2012; 53:3858-64. [PMID: 22562519 DOI: 10.1167/iovs.11-9145] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To investigate whether neuronal activity within the supraoculomotor area (SOA-monosynaptically connected to medial rectus motoneurons and encode vergence angle) of strabismic monkeys was correlated with the angle of horizontal misalignment and therefore helps to define the state of strabismus. METHODS Single-cell neural activity was recorded from SOA neurons in two monkeys with exotropia as they performed eye movement tasks during monocular viewing. RESULTS Horizontal strabismus angle varied depending on eye of fixation (dissociated horizontal deviation) and the activity of SOA cells (n = 35) varied in correlation with the angle of strabismus. Both near-response (cells that showed larger firing rates for smaller angles of exotropia) and far-response (cells that showed lower firing rates for smaller angles of exotropia) cells were identified. SOA cells showed no modulation of activity with changes in conjugate eye position as tested during smooth-pursuit, thereby verifying that the responses were related to binocular misalignment. SOA cell activity was also not correlated with change in horizontal misalignment due to A-patterns of strabismus. Comparison of SOA population activity in strabismic animals and normal monkeys (described in the literature) show that both neural thresholds and neural sensitivities are altered in the strabismic animals compared with the normal animals. CONCLUSIONS SOA cell activity is important in determining the state of horizontal strabismus, possibly by altering vergence tone in extraocular muscle. The lack of correlated SOA activity with changes in misalignment due to A/V patterns suggest that circuits mediating horizontal strabismus angle and those that mediate A/V patterns are different.
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Affiliation(s)
- Vallabh E Das
- College of Optometry, University of Houston, TX 77204, USA.
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9
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Das VE. Cells in the supraoculomotor area in monkeys with strabismus show activity related to the strabismus angle. Ann N Y Acad Sci 2011; 1233:85-90. [PMID: 21950980 DOI: 10.1111/j.1749-6632.2011.06146.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have earlier shown that monkeys reared with daily alternating monocular occlusion for the first few months of life develop large horizontal strabismus, A/V patterns, dissociated vertical deviation (DVD), and dissociated horizontal deviation (DHD). Here, we present results from neurophysiological experiments that show that neuronal activity of cells within the supraoculomotor area (SOA) of juvenile strabismic monkeys is correlated with the angle of strabismus. There was no modulation of SOA cell activity with conjugate eye position as tested during horizontal smooth pursuit. Comparison of SOA population activity in these strabismic animals and normal monkeys (described in the literature) suggests that both vergence (misalignment in the case of the strabismic animals) thresholds and vergence position sensitivities are different in the strabismic animals compared to the normals. Our data suggest that activity within the SOA cells is important in determining the state of horizontal strabismus possibly by altering vergence tone in extraocular muscle.
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Affiliation(s)
- Vallabh E Das
- College of Optometry, University of Houston, Houston, Texas 77204, USA.
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Kim EH, Vicci VR, Han SJ, Alvarez TL. Sustained fixation induced changes in phoria and convergence peak velocity. PLoS One 2011; 6:e20883. [PMID: 21698110 PMCID: PMC3117850 DOI: 10.1371/journal.pone.0020883] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Accepted: 05/11/2011] [Indexed: 02/05/2023] Open
Abstract
PURPOSE This study sought to investigate the influence of phoria adaptation on convergence peak velocity from responses located at different initial vergence positions. METHODS Symmetrical 4° convergence step responses and near dissociated phoria (measured at 40 cm from the subject's midline) were recorded from six subjects with normal binocular vision using an infrared limbus tracking system with a haploscope. Two different sustained fixations (1° and 16° convergent rotation along the subject's midline) were used to study whether phoria had an influence on the peak velocity of convergence responses located at two initial vergence positions (1° or 'far' steps and 12° or 'near' steps). RESULTS Phoria was significantly adapted after a sustained fixation task at near (16°) and far (1°) (p<0.002). A repeated measures ANOVA showed that convergence far steps were significantly faster than the near steps (p<0.03). When comparing convergence steps with the same initial vergence position, steps measured after near phoria adaptation were faster than responses after far adaptation (p<0.02). A regression analysis demonstrated that the change in phoria and the change in convergence peak velocity were significantly correlated for the far convergence steps (r = 0.97, p = 0.001). A weaker correlation was observed for the near convergence steps (r = 0.59, p = 0.20). CONCLUSION As a result of sustained fixation, phoria was adapted and the peak velocity of the near and far convergence steps was modified. This study has clinical considerations since prisms, which evoke phoria adaptation, can be prescribed to help alleviate visual discomfort. Future investigations should include a systematic study of how prisms may influence convergence and divergence eye movements for those prescribed with prisms within their spectacles.
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Affiliation(s)
- Eun H. Kim
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States of America
| | - Vincent R. Vicci
- Department of Vision, Private Practice, Westfield, New Jersey, United States of America
| | - Sang J. Han
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States of America
| | - Tara L. Alvarez
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States of America
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Vision therapy in adults with convergence insufficiency: clinical and functional magnetic resonance imaging measures. Optom Vis Sci 2011; 87:E985-1002. [PMID: 21057347 DOI: 10.1097/opx.0b013e3181fef1aa] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE This research quantified clinical measurements and functional neural changes associated with vision therapy in subjects with convergence insufficiency (CI). METHODS Convergence and divergence 4° step responses were compared between 13 control adult subjects with normal binocular vision and four CI adult subjects. All CI subjects participated in 18 h of vision therapy. Clinical parameters quantified throughout the therapy included: nearpoint of convergence, recovery point of convergence, positive fusional vergence at near, near dissociated phoria, and eye movements that were quantified using peak velocity. Neural correlates of the CI subjects were quantified with functional magnetic resonance imaging scans comparing random vs. predictable vergence movements using a block design before and after vision therapy. Images were quantified by measuring the spatial extent of activation and the average correlation within five regions of interests (ROI). The ROIs were the dorsolateral prefrontal cortex, a portion of the frontal lobe, part of the parietal lobe, the cerebellum, and the brain stem. All measurements were repeated 4 months to 1 year post-therapy in three of the CI subjects. RESULTS Convergence average peak velocities to step stimuli were significantly slower (p = 0.016) in CI subjects compared with controls; however, significant differences in average peak velocities were not observed for divergence step responses (p = 0.30). The investigation of CI subjects participating in vision therapy showed that the nearpoint of convergence, recovery point of convergence, and near dissociated phoria significantly decreased. Furthermore, the positive fusional vergence, average peak velocity from 4° convergence steps, and the amount of functional activity within the frontal areas, cerebellum, and brain stem significantly increased. Several clinical and cortical parameters were significantly correlated. CONCLUSIONS Convergence peak velocity was significantly slower in CI subjects compared with controls, which may result in asthenopic complaints reported by the CI subjects. Vision therapy was associated with and may have evoked clinical and cortical activity changes.
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Priot AE, Laboissière R, Plantier J, Prablanc C, Roumes C. Partitioning the components of visuomotor adaptation to prism-altered distance. Neuropsychologia 2011; 49:498-506. [DOI: 10.1016/j.neuropsychologia.2010.11.028] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 11/14/2010] [Accepted: 11/22/2010] [Indexed: 10/18/2022]
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Vergence adaptation in clinical vergence testing. ACTA ACUST UNITED AC 2010; 81:469-75. [PMID: 20655282 DOI: 10.1016/j.optm.2010.01.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 01/19/2010] [Accepted: 01/25/2010] [Indexed: 11/22/2022]
Abstract
BACKGROUND The purposes of this investigation were to determine whether vergence adaptation occurs after vergence range testing and vergence facility testing and to determine whether vergence adaptation correlates with the results of these tests. METHODS Thirty subjects participated in 3 testing sessions on different days. During each session 1 of the following was tested: base-out prism bar vergences, vergence facility (12 base-out/3 base-in binocular prism flippers for 1 minute), and 5 minutes viewing with 6 prism diopters of base-out prism. Before and after each test, the near phoria was measured using the modified Thorington method. RESULTS There was no correlation between the amplitude of the vergence ranges and the amplitude of vergence facility. Significant vergence adaptation as indicated by an esophoric shift of approximately 3 prism diopters occurred in all testing sessions. The amplitude of vergence adaptation did not correlate with either the amplitude of the blur vergence range or vergence facility. There was a significant correlation between the amplitude of vergence adaptation and the amplitude of the break vergence range. CONCLUSIONS The lack of correlation between the blur vergence range and the vergence facility is not likely because of vergence adaptation. The lack of correlation between the break vergence range and the vergence facility may be in part caused by vergence adaptation.
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Thiagarajan P, Lakshminarayanan V, Bobier WR. Effect of vergence adaptation and positive fusional vergence training on oculomotor parameters. Optom Vis Sci 2010; 87:487-93. [PMID: 20473234 DOI: 10.1097/opx.0b013e3181e19ec2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE Clinical studies have shown that positive fusional vergence (PFV) can be trained through a program of orthoptic exercises. Models of accommodation and vergence predict that training PFV would require a reduction in the convergence accommodation (CA) cross-link. Recent investigations have found that the CA/C ratio is not changed in a clinical population after orthoptics. We hypothesized that such orthoptic programs may instead act to reduce CA through changes in the relationship between fast and slow vergence components. METHODS.: Eleven visually normal subjects were tested. Phoria adaptation to a 12-Delta base-out (BO) wedge prism and the resulting CA responses were monitored every 3 min for 15 min to a DoG target at 0.4 m. These measures were repeated after 2 weeks of orthoptics. Phorias, stimulus accommodative convergence (AC)/A and CA/C ratios, and PFV amplitudes at near were also determined. Before the orthoptics program, these measures were repeated under "adapted" conditions. RESULTS Phoria adaptation following prolonged viewing through the 12-Delta BO wedge prism was associated with a concomitant reduction in the CA. These changes were asymptotic over time with 95% of the change occurring within the first 3 to 6 min. After 2 week of orthoptics, the rates and magnitudes of both phoria adaptation and CA reduction increased significantly (p < 0.01). PFV at 40-cm limits showed increases with orthoptics and under vergence adaptation. CA/C and AC/A ratios were unchanged after orthoptics, but the former was reduced, and the latter increased under the vergence adapted condition. CONCLUSIONS Orthoptics acts to change the time constant and magnitude of vergence adaptation to BO prisms, which leads to a concomitant reduction of CA over a similar time course. This process appears to underlie the increase in positive fusion limits. Although reductions in CA/C ratio occur under the vergence adapted state, this ratio is not directly changed with orthoptics.
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Han SJ, Guo Y, Granger-Donetti B, Vicci VR, Alvarez TL. Quantification of heterophoria and phoria adaptation using an automated objective system compared to clinical methods. Ophthalmic Physiol Opt 2010; 30:95-107. [PMID: 19682268 DOI: 10.1111/j.1475-1313.2009.00681.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Sang J Han
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, USA
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Lee YY, Granger-Donetti B, Chang C, Alvarez TL. Sustained convergence induced changes in phoria and divergence dynamics. Vision Res 2009; 49:2960-72. [PMID: 19781567 DOI: 10.1016/j.visres.2009.09.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2008] [Revised: 09/18/2009] [Accepted: 09/18/2009] [Indexed: 11/26/2022]
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Bossong H, Swann M, Glasser A, Das VE. Applicability of infrared photorefraction for measurement of accommodation in awake-behaving normal and strabismic monkeys. Invest Ophthalmol Vis Sci 2008; 50:966-73. [PMID: 19029024 DOI: 10.1167/iovs.08-2686] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE This study was designed to use infrared photorefraction to measure accommodation in awake-behaving normal and strabismic monkeys and describe properties of photorefraction calibrations in these monkeys. METHODS Ophthalmic trial lenses were used to calibrate the slope of pupil vertical pixel intensity profile measurements that were made with a custom-built infrared photorefractor. Day to day variability in photorefraction calibration curves, variability in calibration coefficients due to misalignment of the photorefractor Purkinje image and the center of the pupil, and variability in refractive error due to off-axis measurements were evaluated. RESULTS The linear range of calibration of the photorefractor was found for ophthalmic lenses ranging from -1 D to +4 D. Calibration coefficients were different across monkeys tested (two strabismic, one normal) but were similar for each monkey over different experimental days. In both normal and strabismic monkeys, small misalignment of the photorefractor Purkinje image with the center of pupil resulted in only small changes in calibration coefficients, that were not statistically significant (P>0.05). Off-axis measurement of refractive error was also small in the normal and strabismic monkeys (approximately 1 D to 2 D) as long as the magnitude of misalignment was <10 degrees. CONCLUSIONS Remote infrared photorefraction is suitable for measuring accommodation in awake, behaving normal, and strabismic monkeys. Specific challenges posed by the strabismic monkeys, such as possible misalignment of the photorefractor Purkinje image and the center of the pupil during either calibration or measurement of accommodation, that may arise due to unsteady fixation or small eye movements including nystagmus, results in small changes in measured refractive error.
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Affiliation(s)
- Heather Bossong
- Division of Sensory-Motor Systems, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30322, USA
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18
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Emoto M, Niida T, Okano F. Repeated Vergence Adaptation Causes the Decline of Visual Functions in Watching Stereoscopic Television. ACTA ACUST UNITED AC 2005. [DOI: 10.1109/jdt.2005.858938] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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19
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Abstract
Our current knowledge of the neural bases of vergence and accommodation has increased significantly over the past few years. The behavior of medial rectus motoneurons during vergence, which has been reported by a number of investigators, is described. The behavior of Edinger-Westphal neurons during accommodation is also described, as are the characteristics of midbrain near-response neurons in the supraoculomotor area. Evidence that some of these near-response neurons provide the vergence input to medial rectus motoneurons and possibly the accommodation input to Edinger-Westphal neurons is reviewed. Anatomical studies have shown that the midbrain near-response region receives input from two deep cerebellar nuclei, the posterior interposed and the fastigial nucleus. Single-unit recording in the posterior interposed nucleus has revealed cells that increase their activity during the far-response, and the behavior of these neurons is reviewed. In addition, studies of a precerebellar nucleus, the nucleus reticularis tegmenti pontis, have revealed some cells that increase their activity during the near-response and others that do so during the far-response. The behavior of these neurons is reviewed. This review documents the great strides that are occurring in our understanding of the anatomy and physiology of the neural pathways controlling vergence and accommodation in the primate.
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Affiliation(s)
- P D Gamlin
- Vision Science Research Center, University of Alabama at Birmingham 35294, USA
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20
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Zhang H, Gamlin PD. Neurons in the posterior interposed nucleus of the cerebellum related to vergence and accommodation. I. Steady-state characteristics. J Neurophysiol 1998; 79:1255-69. [PMID: 9497407 DOI: 10.1152/jn.1998.79.3.1255] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The present study used single-unit recording and electrical microstimulation techniques in alert, trained rhesus monkeys to examine the involvement of the posterior interposed nucleus (IP) of the cerebellum in vergence and accommodative eye movements. Neurons related to vergence and ocular accommodation were encountered within a circumscribed region of the IP and their activity during changes in viewing distance was characterized. The activity of these neurons increased with decreases in vergence angle and accommodation (the far-response) but none showed changes in activity during changes in conjugate eye position and we therefore term them "far-response neurons." Far-response neurons were found within a restricted region of the IP that extended approximately 1 mm rostrocaudally and mediolaterally and 2 mm dorsal to the fourth ventricle. Microstimulation of this far-response region of the IP with low currents (<30 microA) often elicited divergence and accommodation for far. The behavior of 37 IP far-response neurons was examined during normal binocular viewing, during monocular viewing (blur cue alone), and during binocular viewing with accommodation open-loop (disparity cue alone). The activity of all cells was modulated under all three conditions. However, the change in activity of some of these neurons was significantly different under these three viewing conditions. The behavior of 70 IP far-response neurons was compared during normal binocular viewing and during viewing in which the accommodative response was significantly dissociated from the vergence response. The data from these two conditions was pooled and multiple regression analyses for each neuron generated two coefficients expressing the activity of the neuron relative to the vergence and to accommodative response respectively. On the basis of these coefficients, the overall activity of the neurons were classified as follows: 34 positively correlated with divergence, 11 positively correlated with far accommodation, 14 positively correlated with divergence and far accommodation, 9 positively correlated with divergence and accommodation, and 2 positively correlated with convergence and far accommodation. The results of this study demonstrate the involvement of a specific region of the posterior interposed nucleus of the cerebellum in vergence and accommodation. IP far-response neurons are active for vergence and accommodation irrespective of whether or not these eye movements are elicited by blur or disparity cues. The data in the present study strongly suggest that this cerebellar region is a far-response region that is involved in vergence as well as accommodative eye movements.
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Affiliation(s)
- H Zhang
- Vision Science Research Center, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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21
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Abstract
BACKGROUND Congenital central hypoventilation syndrome (CCHS) is a rare cause of central sleep apnea. Although ophthalmic abnormalities have been reported, the ocular findings have not been discussed in detail. METHODS We examined or obtained the records of 37 children with CCHS. RESULTS Twenty-seven patients were found to have abnormal pupils, most of which were miotic and reacted poorly to light. In 18 cases, the anterior surface of the iris was unusually smooth. Ten of the children with abnormal pupils also demonstrated light-near dissociation. Twenty had strabismus of various types, and 18 showed evidence of convergence insufficiency. CONCLUSIONS The high incidence of strabismus, pupillary abnormalities, and convergence insufficiency may be a result of neurologic defects in the midbrain.
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Affiliation(s)
- D S Goldberg
- LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans, USA
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22
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Gamlin PD, Yoon K, Zhang H. The role of cerebro-ponto-cerebellar pathways in the control of vergence eye movements. Eye (Lond) 1996; 10 ( Pt 2):167-71. [PMID: 8776444 DOI: 10.1038/eye.1996.42] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Single-unit recording and anatomical techniques have been used in Rhesus monkeys to investigate the central pathways involved in the neural control of vergence and ocular accommodation. Anatomical studies have revealed connections between the midbrain near-response region and the posterior interposed (IP) and fastigial nuclei of the cerebellum. Single-unit recording studies in the IP of alert, trained monkeys identified cells with activity that increased with increases in the amplitude of divergence and far accommodation, i.e. the far-response. Microstimulation at the site of these neurons often produced a far-response. Single-unit recording from a precerebellar nucleus, the nucleus reticularis tegmenti pontis (NRTP), identified some cells with activity that linearly increased with increases in the amplitude of the near-response, and some with activity that linearly increased with increases in the amplitude of the far-response. Microstimulation at the site of these near- or far-response neurons often produced changes in vergence angle and accommodation. Single-unit recording studies in the region of the frontal eye fields identified cells in the prearcuate cortex with activity that is modulated by either the near- or far-response. These results suggest that regions of the prearcuate cortex, the NRTP and the IP form part of a cerebro-ponto-cerebellar pathway modulating or controlling vergence and ocular accommodation.
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Affiliation(s)
- P D Gamlin
- Vision Science Research Center, University of Alabama at Birmingham 35294, USA
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23
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Abstract
The geometrical requirements for binocular fusion are stated, and the main features of horizontal vergence eye movements are described, together with an influential schema of understanding the interaction between vergence and accommodation. The anatomy and physiology of the midbrain region implicated in vergence and accommodation control are discussed. The cortical areas from which suitable sensory signals might be derived are mentioned briefly, and a speculation is made about esotropia.
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Affiliation(s)
- S J Judge
- University Laboratory of Physiology, Oxford, UK.
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Bando T, Hara N, Takagi M, Yamamoto K, Toda H. Roles of the lateral suprasylvian cortex in convergence eye movement in cats. PROGRESS IN BRAIN RESEARCH 1996; 112:143-56. [PMID: 8979826 DOI: 10.1016/s0079-6123(08)63326-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Ocular convergence and lens accomodation were evoked by microstimulation in the lateral suprasylvian area (LS cortex) in the parieto-occipital cortex in the cat. Electrolytic lesions in LS cortex reduced the amplitude and velocity of ocular convergence. Neurons in LS cortex discharged in relation to ocular convergence and/or lens accommodation. These results support the hypothesis that the LS cortex plays an important role in controlling ocular convergence The LS cortex receives visual inputs from cortical visual areas 17, 18 and 19, and in addition from the superior colliculus through the LP nucleus of the thalamus. Electrophysiological recordings have revealed that these visual inputs, which include cues about 3-dimensional target motion, are integrated in the LS cortex. The integrated output from LS cortex may provide the brainstem motor centers with the neural signals that facilitate eye movements, especially when the target is moving at high speeds. Outputs from the LS cortex travel directly to brainstem structures including the superior colliculus and pretectum. Evidence from monkey suggests that information may also travel to the mesencephalic reticular formation, where neurons have been recorded that are related to ocular convergence, lens accomodation or both. Although comparable data is lacking in the cat, it is suggested that the efferent circuit from the LS cortex to the motor nuclei in the brainstem included both the superior colliculus and the mesencephalic reticular formation. It is also suggested that this pathway is rather short, given that the mean latency of the early component of evoked disjunctive eye movements was approximately 60 ms.
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Affiliation(s)
- T Bando
- Department of Physiology, Niigata University School of Medicine, Japan.
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25
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Takagi M, Toda H, Bando T. Extrastriate cortical neurons correlated with ocular convergence in the cat. Neurosci Res 1993; 17:141-58. [PMID: 8233119 DOI: 10.1016/0168-0102(93)90091-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Responses of neurons in the lateral suprasylvian area to visual stimulation in association with ocular convergence were studied in eight alert cats trained to track a visual target moving in depth. Activities of 18 (3%) of 659 cells were related to ocular convergence. These 18 neurons were divided into two groups: activities of seven neurons (40%) correlated with peak velocities of convergence eye movement at both fast and slow target speeds (group I), while those of five neurons (30%) correlated with them only at faster target speed (group II). Activities of six other neurons correlated with peak velocity of ocular convergence at faster target speed but were not tested at slower speed. Activities of four group-I neurons (60%) did not or only weakly correlate with lens accommodation, while those of four group-II neurons (80%) correlated with peak velocity or amplitude of lens accommodation. It can therefore be concluded that the four group-I neurons are primarily related to ocular convergence. Other cells were either convergence-related, lens accommodation-related or both. It is suggested that these different types of neurons contribute in combination to optimal control of convergence eye movement.
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Affiliation(s)
- M Takagi
- Department of Physiology, Niigata University School of Medicine, Japan
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