Degenerative Diseases of the Central Nervous System Clinical Trial
The purpose of eye movements is to ensure clear, optimal vision. In order to see clearly,
images must be held steady on the retina. Best visual acuity is achieved when the image of
the object of interest is brought to and held on the fovea of the retina. Two main types of
eye movements are responsible for that: those that keep images stable on the retina (gaze
holding mechanisms) and those that change the line of sight (gaze shifting mechanisms).
Several functional classes of eye movements have been defined; each has distinctive
physiological properties that suit best to its particular task. Thus, vestibular and
optokinetic eye movements hold images of the seen world steady on the retina during
perturbations of the head. Saccades are rapid eye movements that bring the image of an
object of interest, detected in the periphery of vision, onto the fovea where it can be seen
best. Smooth pursuit eye movements place the images of a moving target close to fovea.
Vergence eye movements place the images of a single object simultaneously onto both foveae.
Each functional class of eye movements relies on a different neural substrate. The clinical
significance of it is that impairment of a specific class of eye movement points to
involvement of distinct structures or pathways within the brain. Thus, abnormalities of
ocular motility are often the clue to the anatomical localization of neurological disorders.
Significance: This study will contribute to understand how the brain governs production of
eye movements, and provide better insight on interaction between sensory (visual) and motor
(eye movement) system, i.e. sensory-motor interaction. It will also contribute to identify
pathophysiological mechanisms underlying human diseases and will improve the investigators'
ability to diagnose and encourage development of new therapeutic strategies.
Methods: The investigators will measure eye and head movements using the magnetic scleral
search coil technique. The magnetic search coil technique is the most sensitive and accurate
technique used in modern ocular motor and vestibular research for measuring horizontal,
vertical and torsional eye movements. The coils are easy to apply and well tolerated over a
wearing period of up to 45 minutes per recording session.
Population: A grand total of about 250 individuals (normal subjects and patients) will be
recruited for the study. Patients will be recruited from the in- and out-patients of the
Neurology and Neuro-ophthalmology services of Meir Medical Center. Healthy normal subjects
will be recruited from faculty and staff of Meir Medical Center.
Criteria for inclusion/exclusion: The investigators will study patients with neurological
disorders causing abnormal eye movements: Degenerative CNS diseases, extrapyramidal
disorders, Spino-cerebellar ataxias, Cerebrovascular diseases, demyelinating diseases,
Ocular motor and vestibular palsies, Mitochondrial and other ocular myopathies. Only
patients who are medically stable and are able to give informed consent will be included in
the study. Criteria for excluding subjects will include eye disease such as corneal or
scleral abrasion or disease, glaucoma, refractive errors greater than 2 diopters and
concurrent medication with CNS-active agents.
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Observational Model: Cohort, Time Perspective: Prospective