Visual fatigue effects on vergence dynamics in asymptomatic individuals

Thiagarajan, Preethi; Ciuffreda, Kenneth J.

doi:10.1111/opo.12083

Cited by 6 publications

(4 citation statements)

References 37 publications

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“…4 This is thought to be caused by a centrally-based, neurological mismatch between the accommodative and vergence response to visual stimuli, not simply muscle fatigue in the extraocular muscles. 10 This suggests that differences in brain activity may be observable in imaging studies of individuals with CI.…”

Section: Baseline Proceduresmentioning

confidence: 99%

Imaging of Convergence Insufficiency Treatment Effects (ICITE) Pilot Study: Design and Methods

2017

VDR

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Background: The blood-oxygen-level-dependent (BOLD) signal from functional magnetic resonance imaging (fMRI) identifies brain activation during specific tasks.1,2 This paper describes the design and methodology of the Imaging of Convergence Insufficiency Treatment Effects (ICITE) Study, a two-phase study comparing BOLD activations during vergence eye movements in symptomatic convergence insufficiency (CI) subjects (1) to those with normal binocular vision (NBV) and (2) after office-based vergence/accommodative therapy (OBVAT) versus office-based placebo therapy (OBPT). Methods: Young adults, 18 to 30 years, with NBV or symptomatic CI (near exophoria at least 4Δ [prism diopters] greater than at distance, receded near point of convergence [NPC], and insufficient positive fusional vergence [PFV]) were enrolled. During fMRI scanning, subjects were instructed to fuse a random-dot stereogram stimulus with vergence demands ranging from -3Δ to +25Δ. CI subjects were then randomized to 12 weeks of OBVAT or OBPT. Vision and fMRI examination at outcome were performed by a masked examiner. BOLD signal at baseline was compared between NBV and CI patients. Later, the BOLD response at baseline was compared to that following vision therapy for those with CI. Conclusion: The imaging results are expected to advance understanding of neurological mechanisms of CI and the effects of therapy on the vergence system, which in turn may guide development of future research that could lead to new treatment strategies.

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Section: Baseline Proceduresmentioning

confidence: 99%

Imaging of Convergence Insufficiency Treatment Effects (ICITE) Pilot Study: Design and Methods

2017

VDR

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“…However, the fact that it did not increase more could also be attributed to increasing fatigue. In the literature, fatigue is said to contribute remarkably to missing or existing changes of vergence dynamics for repeated vergence eye movements (Thiagarajan & Ciuffreda, 2013).…”

Section: Vergence Dynamicsmentioning

confidence: 99%

“…Over 100 years ago, Bielschowsky (1907) made the clinical observation that an incomitant strabismus becomes increasingly concomitant over time, also called ''spread of comitance'' (von Noorden & Campos, 2002) or ''orthophorization'' (Kaufmann, 2004;Leigh & Zee, 2006). Its underlying mechanisms are not yet understood.…”

Section: Introductionmentioning

confidence: 99%

Gaze-dependent phoria and vergence adaptation

Dysli

Abegg

2016

Journal of Vision

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Incomitance is a condition with gaze-dependent deviations of ocular alignment and is common in strabismus patients. The physiological mechanisms that maintain equal horizontal ocular alignment in all gaze directions (concomitance) in healthy individuals are poorly explored. We investigate adaptive processes in the vergence system that are induced by horizontal incomitant vergence stimuli (stimuli that require a gaze-dependent vergence response in order to re-establish binocular single vision). We measured horizontal vergence responses elicited after healthy subjects shifted their gaze from a position that required no vergence to a position that required convergence. Repetitive saccades into a position with a convergence stimulus rapidly decreased phoria (defined as the deviation of ocular alignment in the absence of a binocular stimulus). This change of phoria was present in all viewing directions (from 0° to 0.86° ± 0.40°, p < 0.001) but was more pronounced in the gaze direction with a convergence stimulus (from 0.26° ± 0.13° to 1.39° ± 0.33°, p < 0.001). We also found that vergence velocity rapidly increased (p = 0.015) and vergence latency promptly decreased (p < 0.001). We found gaze-dependent modulation of phoria in combined saccade-vergence eye movements and also in pursuit-vergence eye movements. Thus, acute horizontal, gaze-dependent changes of vergence, such as may be encountered in new onset strabismus due to paralysis, can rapidly increase vergence velocity and decrease latency. Gaze-specific (concomitant) and gaze-independent (incomitant) phoria levels will adapt. These early adaptive processes increase the efficacy of binocular vision and maintain good ocular alignment in all directions of gaze.

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“…In today's society, the use of digital devices has significantly increased in all age groups, and the visual system may not be able to effectively maintain long periods of overloaded close visually based work, leading to asthenopia. Asthenopia refers to the long-term excessive activity of the visual organs (Long et al, 2017), especially the intraocular and extraocular muscles, such as ciliary muscles, which play a major role in focusing the eyes on close objects (Smith, 1973;Thiagarajan and Ciuffreda, 2013a), and the medial and lateral rectus muscles whose heterotropic movements dominate the convergence and divergence of the eyes (Thiagarajan and Ciuffreda, 2013b). The clinical symptoms of asthenopia usually manifest as an inability to maintain short-distance work, itching, pain around the eyes and orbit, blurred vision, tearing, photophobia, dryness, foreign-body sensation (Sheedy et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Functional Neuroanatomy of the Human Accommodation Response to an “E” Target Varying from -3 to -6 Diopters

Chen

Tan

et al. 2020

Front. Integr. Neurosci.

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Background: We aimed to identify the functional brain networks involved in the regulation of visual accommodation by contrasting the cortical functional areas evoked by foveal fixation to an "E" target, which were subservient to the accommodation responses to a -3/-6 diopter stimulus.Methods: Neural activity was assessed in healthy volunteers by changes in blood oxygen level-dependent (BOLD) signals measured with functional magnetic resonance imaging (fMRI). Twenty-five right-handed subjects viewed the "E" target presented in a hierarchical block design. They participated in two monocular tasks: (i) sustained foveal fixation upon an "E" target on a white background at 33 cm (-3.03D accommodative demand); and (ii) sustained fixation through an attached -3D concave lens (-6D accommodative demand) in front of the fixated eye; each condition cycled through a standard alternating 30-s eye open/30-s eye closed design to provide the BOLD contrast. The total sustained period was 480 s. Results:The contrast between the -3D and the rest condition revealed activation in the occipital lobe (Lingual gyrus, Cuneus, Calcarine_L, and Calcarine_R); cerebellum (Cerebellum_Crus1_L and Cerebellum_6_L); precentral lobe (Precentral_R); frontal lobe (Frontal_Inf_Oper_R and Frontal_Mid_R); and cingulate cortex (Cingulum_Ant_L). With the -3D concave lenses (-6D accommodative demand) in front of the fixated eye, the voxel size and peak intensity of activation in the occipital lobe and cerebellum were greater than with the -3D accommodative demand; emergent activated brain areas included the parietal lobe (bilateral precuneus gyrus and right supramarginal gyrus); the precentral lobe and cingulate cortex failed to reach the threshold in the -6D vs. rest contrast. In the -3D and -6D contrast comparison, the frontal lobe (Frontal_Sup_Medial_L) and parietal lobe

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Visual fatigue effects on vergence dynamics in asymptomatic individuals

Cited by 6 publications

References 37 publications

Imaging of Convergence Insufficiency Treatment Effects (ICITE) Pilot Study: Design and Methods

Imaging of Convergence Insufficiency Treatment Effects (ICITE) Pilot Study: Design and Methods

Gaze-dependent phoria and vergence adaptation

Functional Neuroanatomy of the Human Accommodation Response to an “E” Target Varying from -3 to -6 Diopters

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