Reeducation of vergence dynamics improves postural control

Can Saccade and Vergence Properties Discriminate Stroke Survivors from Individuals with Other Pathologies? A Machine Learning Approach

Recent studies applying machine learning (ML) to saccade and vergence eye movements have demonstrated the ability to distinguish individuals with dyslexia, learning disorders, or attention disorders from healthy individuals or those with other pathologies. Stroke patients are known to exhibit visual deficits and eye movement disorders. This study focused on saccade and vergence measurements using REMOBI technology V3 and the Pupil Core eye tracker. Eye movement data were automatically analyzed with the AIDEAL V3 (Artificial Intelligence Eye Movement Analysis) cloud software developed by Orasis-Ear. This software computes multiple parameters for each type of eye movement, including the latency, accuracy, velocity, duration, and disconjugacy. Three ML models (logistic regression, support vector machine, random forest) were applied to the saccade and vergence eye movement features provided by AIDEAL to identify stroke patients from other groups: a population of children with learning disorders and a population with a broader spectrum of dysfunctions or pathologies (including children and adults). The different classifiers achieved macro F1 scores of up to 75.9% in identifying stroke patients based on the saccade and vergence parameters. An additional ML analysis using age-matched groups of stroke patients and adults or seniors reduced the influence of large age differences. This analysis resulted in even higher F1 scores across all three ML models, as the comparison group predominantly included healthy individuals, including some with presbycusis. In conclusion, ML applied to saccade and vergence eye movement parameters, as measured by the REMOBI and AIDEAL technology, is a sensitive method for the detection of stroke-related sequelae. This approach could be further developed as a clinical tool to evaluate recovery, compensation, and the evolution of neurological deficits in stroke patients.

Pierre-Marie Gagey and the Evolution of Posturology: Unraveling the Complexity of the Fine Postural Control System

The subtle sway of human standing posture began to be studied in the 19th century. Since then, numerous approaches - from the early statokinesiometers to the more advanced force platforms or 3D-posture recording systems - have been developed to understand human postural control physiology and its clinical implications. French physician Pierre-Marie Gagey made significant contributions to the field of posturology, a discipline focused on the intricacies of human postural control. From the 1950s, he advanced the field through observation and experimentation, particularly exploring the relationship between postural muscle tone and the fine postural control system. Gagey's collaboration with researchers of that time led to the refinement of stabilometry, a technique for measuring body sway in standing positions. Throughout his career, Gagey worked across multiple disciplines, including ophthalmology, podiatry, psychology, and the study of the vestibular and stomatognathic systems, to develop a comprehensive approach to postural assessment and treatment. His efforts culminated in the standardization of stabilometry, ensuring consistent and accurate measurements across different platforms. Gagey's work emphasized the complexity of postural control, highlighting the integration of peripheral and central nervous system inputs in maintaining balance. His research has left an enduring impact on the field of posturology, providing a framework for understanding and treating postural disorders. Pierre-Marie Gagey passed away in 2023, but his pioneering contributions continue to influence the study and clinical practice of human postural control. This narrative review aims to pay tribute to Dr. Gagey's career and research activity.

Cervical Spine Vibration Modifies Oculomotor Function in Young Adults with Traumatic Brain Injury

OBJECTIVE

The purpose of this study was to investigate if vibrational interference of spinal proprioception affects oculomotor function, visual attention and processing, and selective attention in individuals with mild traumatic brain injury (mTBI) compared to healthy age-matched controls.

METHODS

This study was a parallel design, single-session intervention with 20 young adults with mTBI and 20 age-matched controls. Each completed a battery of computerized eye-tracking assessments (CEAs), including egocentric localization, fixational stability, smooth pursuit, saccades, Stroop, and the vestibulo-ocular reflex (VOR), and then had their cervical spine function (flexion-relaxation ratio) recorded at baseline. Spinal vibration (100 Hz) was applied to the cervical spine and the CEA battery was repeated. CEA outcomes were compared to baseline and between mTBI and control groups.

RESULTS

Following cervical vibration, significant pre to post-differences were seen in both the mTBI and control group for egocentric localization, fixation stability, pursuit, saccades, Stroop, and VOR. At baseline, there was a significant difference between the mTBI and control groups across many CEA measures, with the mTBI group performing more poorly in egocentric localization, pursuit, saccades, Stroop, and VOR. The mTBI group also had a poorer flexion-relaxation ratio than the control group.

CONCLUSION

Cervical spine vibration improved cognitive and oculomotor performance in the mTBI group for VOR, Stroop, and pursuit, but had mixed effects on the control group. These findings suggest that some optometric mTBI symptoms may result from spinal or proprioceptive dysfunction, as altering proprioceptive input appears to positively impact visual outcomes.

Post-Traumatic Craniocervical Disorders From a Postural Control Perspective: A Narrative Review

Mild traumatic brain injury (mTBI) and whiplash injury (WI) may lead to long-term disabling consequences known as post-concussive syndrome (PCS) and whiplash-associated disorders (WADs). PCS and WAD patients commonly complain of conditions encompassing dizziness, vertigo, headache, neck pain, visual complaints, anxiety, and neurocognitive dysfunctions. A proper medical work-up is a priority in order to rule out any acute treatable consequences. However investigations may remain poorly conclusive. Gathered in the head and neck structures, the ocular sensorimotor, the vestibular, and the cervical proprioceptive systems, all involved in postural control, may be damaged by mTBI or WI. Their dysfunctions are associated with a wide range of functional disorders including symptoms reported by PCS and WAD patients. In addition, the stomatognathic system needs to be specifically assessed particularly when associated to WI. Evidence for considering the post-traumatic impairment of these systems in PCS and WAD-related symptoms is still lacking but seems promising. Furthermore, few studies have considered the assessment and/or treatment of these widely interconnected systems from a comprehensive perspective. We argue that further research focusing on consequences of mTBI and WI on the systems involved in the postural control are necessary in order to bring new perspective of treatment.

Postural Patterns of the Subjects with Vergence Disorders: Impact of Orthoptic Re-education, a Pilot Study

Aim:

Vergence insufficiency is a common oculomotor disorder which causes visual but also general, and even postural symptoms. This study aimed to characterise postural control of subjects with isolated vergence disorder and assess whether orthoptic therapy affects it.

Method:

Vergence disorders were evaluated and treated by orthoptists. Postural control quality was measured before and after orthoptic therapy in different conditions to study the role of vision, fixating distance, binocular vision and ocular dominance.

Results:

Before orthoptic therapy, we recorded less body sway when subjects had their eyes closed than when they had their eyes open, and also less sway for the binocular condition when compared with monocular viewing conditions. This is opposite to well-known normal behaviour. Moreover, no distance or ocular dominance effect was found. After orthoptic therapy, our subject’s body sway was less when they had their eyes open than with their eyes closed and less when they looked at near fixation. No difference was found between monocular and binocular viewing conditions, but a small advantage of ocular dominance was found for one parameter.

Conclusion:

We conclude that subjects with vergence disorders show postural behaviour that is not characterized by the normal regularities observed in healthy subjects. Orthoptic re-education may have contributed to promoting such regularities. Further studies are needed to confirm these preliminary results.