Fast-phase horizontal eye movement vision Fast-phase vertical eye movement vision<unk>  is highly noticeable but rarely recognized.<unk>  can be clinically investigated by using a number of non-invasive standard tests. The simplest one is the caloric reflex test, in which one ear canal is irrigated with warm or cold water or air. The temperature gradient provokes the stimulation of the horizontal semicircular canal and the consequent<unk> .<unk>  is often very commonly present with Chiari malformation. The resulting movement of the eyes may be recorded and quantified by a special device called an electronystagmograph (ENG), a form of electrooculography (an electrical method of measuring eye movements using external electrodes), or an even less invasive device called a videonystagmograph (VNG), a form of video-oculography (VOG) (a video-based method of measuring eye movements using external small cameras built into head masks), administered by an audiologist. Special swinging chairs with electrical controls can be used to induce rotatory<unk> . Over the past forty years, objective eye-movement-recording techniques have been applied to the study of<unk> , and the results have led to greater accuracy of measurement and understanding of the condition. Orthoptists may also use an optokinetic drum, or electrooculography to assess a patient's eye movements.<unk>  can be caused by subsequent foveation of moving objects, pathology, sustained rotation or substance use.<unk>  is not to be confused with other superficially similar-appearing disorders of eye movements (saccadic oscillations) such as opsoclonus or ocular flutter that are composed purely of fast-phase (saccadic) eye movements, while<unk>  is characterized by the combination of a smooth pursuit, which usually acts to take the eye off the point of focus, interspersed with the saccadic movement that serves to bring the eye back on target. Without the use of objective recording techniques, it may be very difficult to distinguish among these conditions. In medicine, the presence of<unk>  can be benign, or it can indicate an underlying visual or neurological problem. Pathologic<unk>  Pathological<unk>  is characterized by "excessive drifts of stationary retinal images that degrades vision and may produce illusory motion of the seen world: oscillopsia (an exception is congenital<unk> ". When<unk>  occurs without fulfilling its normal function, it is pathologic (deviating from the healthy or normal condition). Pathological<unk>  is the result of damage to one or more components of the vestibular system, including the semicircular canals, otolith organs, and the vestibulocerebellum. Pathological<unk>  generally causes a degree of vision impairment, although the severity of such impairment varies widely. Also, many blind people have<unk> , which is one reason that some wear dark glasses. Variations *Central<unk>  occurs as a result of either normal or abnormal processes not related to the vestibular organ. For example, lesions of the midbrain or cerebellum can result in up- and down-beat<unk> . *Gaze induced<unk>  occurs or is exacerbated as a result of changing one's gaze toward or away from a particular side which has an affected central apparatus. *Peripheral<unk>  occurs as a result of either normal or diseased functional states of the vestibular system and may combine a rotational component with vertical or horizontal eye movements and may be spontaneous, positional, or evoked. *Positional<unk>  occurs when a person's head is in a specific position. An example of disease state in which this occurs is Benign paroxysmal positional vertigo (BPPV). *Post rotational<unk>  occurs after an imbalance is created between a normal side and a diseased side by stimulation of the vestibular system by rapid shaking or rotation of the head. *Spontaneous<unk>  is<unk>  that occurs randomly, regardless of the position of the patient's head. Physiological<unk>  Physiological<unk>  is a form of involuntary eye movement that is part of the vestibulo-ocular reflex (VOR), characterized by alternating smooth pursuit in one direction and saccadic movement in the other direction. Variations The direction of<unk>  is defined by the direction of its quick phase (e.g. a right-beating<unk>  is characterized by a rightward-moving quick phase, and a left-beating<unk>  by a leftward-moving quick phase). The oscillations may occur in the vertical, horizontal or torsional planes, or in any combination. The resulting<unk>  is often named as a gross description of the movement, e.g. downbeat<unk> , upbeat<unk> , seesaw<unk> , periodic alternating<unk> . These descriptive names can be misleading, however, as many were assigned historically, solely on the basis of subjective clinical examination, which is not sufficient to determine the eyes' true trajectory. * Optokinetic (syn. opticokinetic)<unk> : a<unk>  induced by looking at moving visual stimuli, such as moving horizontal or vertical lines, and/or stripes. For example, if one fixates on a stripe of a rotating drum with alternating black and white, the gaze retreats to fixate on a new stripe as the drum moves. This is first a rotation with the same angular velocity, then returns in a saccade in the opposite direction. The process proceeds indefinitely. This is optokinetic<unk> , and is a source for understanding the fixation reflex. * Postrotatory<unk> : if one spins in a chair continuously and stops suddenly, the fast phase of<unk>  is in the opposite direction of rotation, known as the "post-rotatory<unk> ", while slow phase is in the direction of rotation.
Nystagmus
Ocular tremor
Oscillopsia
Mydriasis
Pendular nystagmus
Ocular dysmetria
Horizontal gaze palsy
Ophthalmoparesis