Nystagmus vs saccades

Eye movements - Anatomy, Physiology, Clinical Applications

Inherited Retinal Disease - #EyeWant2Kno

  1. Speak to Your Doctor Today About Genetic Testing For You or Your Loved One
  2. Nystagmus Saccade A saccade is a rapid eye movement(a jump) which is usually conjugate (i.e. both eyes move together in thesame direction) and under voluntary control. Broadly speaking the purpose of these movements is to bring images of particular areas of thevisual world to fal
  3. Purpose of review: This article provides an overview of nystagmus and saccadic intrusions with the goal of facilitating recognition and differentiation of abnormal eye movements to assist with accurate diagnosis of neurologic disease and evidence-based specific treatment of oscillopsia. Myriad advances have been made in the understanding of several types of nystagmus and saccadic intrusions.

  1. Treatment of Nystagmus and Saccadic Oscillations. Matthew J. Thurtell, MBBS FRACP and John J. Brinkley, MD. June 23, 2013 Introduction . Nystagmus is often encountered in ophthalmology practice, having a prevalence of about 24 per 10,000 in the general population.[1
  2. Nystagmus was linked to vestibular stimulation in the 19th century, and Mach, Breuer, and Crum Brown all described its fast and slow phases. Wells and Breuer proposed that there was no visual awareness during the ballistic phase (saccadic suppression)
  3. Optokinetic response movements / postrotatory nystagmus Despite their intimidating names, these two forms of eye movements aren't so complicated. The optokinetic response and postrotatory nystagmus are in essence reflexive combinations of saccadic and smooth pursuit movements, that are also controlled by the vestibulo-ocular system
  4. There are four basic types of eye movements: saccades, smooth pursuit movements, vergence movements, and vestibulo-ocular movements. The functions of each type of eye movement are introduced here; in subsequent sections, the neural circuitry responsible for three of these types of movements is presented in more detail (see Chapters 14 and 19 for further discussion of neural circuitry.

Saccadic oscillations are often mistaken for nystagmus. In contrast to nystagmus, in which there is always a slow-phase eye movement, saccadic oscillations are saccades (rapid refixation eye movements) without any slow phases. 28. What are the characteristics and concerns for ocular flutter Nystagmus more likely to be seen with fixation removed; Nystagmus more likely to be exacerbated when gazing in the direction of the fast component of the jerk nystagmus (Alexander's law) Nystagmus more likely to be exacerbated post horizontal headshake - horizontal nystagmus; Pursuit tracking and saccade performance normal (or age dependent nystagmus Central Saccades Extra involuntary eye movements during horizontal and vertical tracking. Normal saccadic movement: hold the patient's head stationary. Hold your finger about 15 degrees to one side of your nose. Ask the patien If there is a lag in corrective saccades in both directions, it may be concerning for central vertigo. This test can also be performed in the vertical plane. A lag in corrective saccades in the vertical plane is always suspicious for a central etiology for vertigo. Pitfalls: The patient must be awake and cooperative. This is essentially an.

True pendular nystagmus is sinusoidal, whereas jerk nystagmus has a slow phase away from the object of regard, followed by a fast (saccadic) phase toward the target. The direction of the fast component, by convention, defines the nystagmus direction. Only accurate recordings can often assess these criteria The goal of treatment is to reduce visual symptoms (e.g., blurred vision, oscillopsia) by reducing the speed of nystagmus slow phases or by suppressing saccadic oscillations. Treatments that stop the eyes from moving altogether (e.g., botulinum toxin injections into the extraocular muscles) are not ideal, because they cause oscillopsia during. Nystagmus is a rhythmic biphasic oscillation of the eyes, and the slow phase eye drift initiates the movement. Nystagmus should also be distinguished from other ocular oscillations or nystagmoid eye movements. These other ocular oscillations usually do not have a slow phase and often represent disorders of saccades. Characteristically, they interrupt foveal fixation, and althoug In jerk nystagmus, the slow (pathologic) phase is followed by the fast (named) phase. Nystagmus should be distinguished from oscillations and intrusions, particularly given disparate localizations and etiologies. These include saccadic intrusions (e.g., square wave jerks) and saccadic oscillations (e.g., ocular flutter, opsoclonus)

Spontaneous nystagmus is nystagmus that occurs randomly, regardless of the position of the patient's head. Physiological nystagmus [ edit ] Physiological nystagmus 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. Spontaneous Nystagmus Test • Record nystagmus in light and dark - Acute vestibular disorders have strong horizontal jjygerk nystagmus. - Normal people and chronic vestibular disorders have little or no nystagmus. Neural compensation for vestibular tone asymmetry is fast and effective. Most people can't fake nystagmus Pathological Nystagmus and Saccadic Intrusions Abnormal eye movements that disrupt steady fixation are of two main types: pathological nystagmus and saccadic intrusions. The essential difference between nystagmus and saccadic intrusions lies in the initial eye movement that takes the line of sight away from the visual target Convergence retraction nystagmus may be elicited with upward saccades (downgoing optokinetic stimulus). Opsoclonus/Saccadomania Saccadic intrusions with conjugate, multidirectional eye movements have been attributed to viral illness, neuroblastoma (children), and visceral carcinoma (adults)

• Nystagmus should be distinguished from nystagmus-like eye movements such as saccadic disorders, myokymia, myorhyth-mia, myoclonus and bobbing • Congenital nystagmus should be consid-ered when an incidental fi nding of nystag-mus does not appear to fi t the rest of the clinical picture • The management of nystagmus is strongl Nystagmus waveforms can be jerky or pendular (Fig. 202-1). If the corrective movements are reflex saccades, the waveform describes a jerk. The slow movements are called slow components or slow phases, and the saccades are called fast components or fast phases. The direction of jerk nystagmus often is designated by the direction of the fas The direction of the saccadic eye movement is important. Unidirectional nystagmus is reassuring and more likely to be of peripheral origin. When nystagmus changes direction or is vertical, it is much more likely to be associated with central pathologies. Bidirectional nystagmus, in particular, is highly specific for stroke PURPOSE OF REVIEW This article provides an overview of nystagmus and saccadic intrusions with the goal of facilitating recognition and differentiation of abnormal eye movements to assist with accurate diagnosis of neurologic disease and evidence-based specific treatment of oscillopsia. Myriad advances have been made in the understanding of several types of nystagmus and saccadic intrusions. Nystagmus is defined by rhythmic, abnormal eye movements with a slow eye movement driving the eye off the target followed by a second movement that brings the eye back to the target.The movement can be horizontal, vertical, torsional or a combination of these movements. Nystagmus can be jerk (named for fast phase) or pendular, variable amplitude and frequency, and can be worsened or improved.

Saccades are fast eye movements that bring the image of an object of interest onto the fovea. They consist of a hierarchy of rapid eye movements, from quick phases of vestibular and optokinetic nystagmus, to reflexive saccades, to higher-level volitional saccades Nystagmus is characterised by the combination of 'slow phases', which usually take the eye off the point of regard, interspersed with saccade-like quick phases that serve to bring the eye back on target

In most cases, dissociated nystagmus is a manifestation of the brain's attempt, with a series of saccades, to put the fovea of the weak, adducting eye on target. 2 Tumours of the cerebellopontine angle may cause a combination of low frequency, large amplitude horizontal nystagmus looking ipsilaterally, because of defective gaze holding, and a. DEFINITION: rhythmical oscillation of the eyeballs (click here for video) at least 37 different kinds are recognized. commonly used to refer to JERKY NYSTAGMUS: . slow drift of the eyes in one direction (PURSUIT) followed by a rapid recovery movement in the opposite direction (SACCADE); direction is named for the fast component: i.e, a rightward nystagmus consists of slow movement of eyes to. Clinical Balance Function Testin

Nystagmus and Saccadic Intrusions - PubMe

Saccades; Pursuit, Saccadic; Saccadic Eye Movements

Types of saccadic eye movements A. Terry Bahill, Ph.D., and B. Todd Troost, M.D. The term saccade is applied to a variety of eye movements, including saccadic refixations, micro - saccades, fast phases of nystagmus, and fast phases of other ocular oscillations. Numerous clinical and theoretical descriptions of saccades have re When looking for asymmetry (between vertical vs horizontal saccades and between left vs. right saccades) fixing on the bridge of the nose can aid the examiner. (unlike nystagmus) and no inter. In AT, hypometric saccades, alternating skew deviation, gaze-evoked nystagmus, downbeat nystagmus, upbeat nystagmus, periodic alternating nystagmus, and square wave jerks can be seen [88-90]. In AT and AOA1, after rotating a patient in a chair, there is prolonged post-rotational nystagmus with fast phase (beating) to the direction of. Convergence-retraction nystagmus, perhaps the most pathognomonic of all type of waveform, presented as adducting saccades (medial rectus contraction). This can occurred spontaneously or during an attempted upward gaze (often accompanied by retraction of the eyes into orbits) Nystagmus is a rhythmic, involuntary movement of the eye. There are two general types. Jerk nystagmus when there is a slow phase movement in one direction, followed by a quick phase movement in the opposite direction. Pendular nystagmus has equal phases in both directions. There are many variations defined by the direction of the quick phase.

Check smooth pursuit and saccades. Saccadic dysmetria also suggests a central etiology. Smooth pursuit can be difficult to assess when significant nystagmus is present, but if vertical pursuit is abnormal when the patient has spontaneous horizontal nystagmus, this is likely a central etiology With saccadic intrusions, the initial eye movement away from the target is a saccade, as opposed to nystagmus in which the initial eye movement is generally a slow phase. More importantly, unlike nystagmus, saccadic intrusions (except for saccadic pulses (3.1.3)) have no slow phase drift

Treatment of Nystagmus and Saccadic Oscillations

Epileptic nystagmus (EN) is a rare sign of seizure activity. We describe eight patients with horizontal EN and hypothesize that the frequency of ictal discharge, anatomic localization of ictal activity, and level of consciousness determine its occurrence and mechanism. We believe that EN is due to epileptic activation of a cortical saccade region; in each case, quick phases were generated away. There was an alternating esotropia, greater at distance than near. Saccades were slow, especially vertically. Elevation and depression were markedly restricted in both eyes. Horizontal gaze was also restricted. She had horizontal gaze-evoked nystagmus and prominent upbeat nystagmus in upgaze. There was no change with oculocephalics Assessment: Check the presence of a nystagmus. Nystagmus is an involuntary, rhytmic, osscilatory eye movement. A spontaneous nystagmus is a reason for referral for specialistic examination, regardless of direction, frequency or speed. Saccadic eye movements [edit | edit source] Performance: The patient quickly changes his gaze from one point to. -VNG can visualize torsional nystagmus.-Vertical tracings are cleaner and more accurate in VNG. VNG vs. ENG: Limitations • VNG - Cannot test patients with ptosis and similar - If prolongation of saccades is evident, the examiner should rule out inattention or uncooperative behavior If nystagmus is present, further examination may provide useful information for disease localisation. This includes observing the nystagmus in various gaze positions and removing fixation by the use of Frenzel's goggles. Saccades. Voluntary saccade initiation should be assessed by instructing the patient to look to the left, right, up, and down

nystagmus, but rather a series of saccades when the patient looks laterally. The abducting eye saccades may be an adaptive attempt by the brain to correct for the hypometric saccades of the weak medial rectus muscle.3 Demyelination and brainstem stroke are the most causes of internuclear ophthalmoplegia. ) Similar ey BACKGROUND/AIMS Abnormalities in the saccadic main sequence are an important finding and may indicate pathology of the ocular motor periphery or central neurological disorders. In young or uncooperative patients it can be difficult eliciting a sufficient number of saccades to measure the main sequence. It is often assumed that the quick phases of optokinetic nystagmus (OKN) are identical to. Nystagmus should be distinguished from inappropriate saccades that prevent steady fixation (e.g. ocular flutter). Saccades are fast movements, and the smeared retinal signal because of these movements remains largely unpreceived. However, patients in whom abnormal saccades repeatedly misdirect the fovea often complain of difficulty in reading Bruns nystagmus (slow and large amplitude nystagmus when looking toward the side of the lesion, and rapid, small-amplitude nystagmus when looking away from the side of the lesion). Hyperventilation nystagmus if present will beat toward the side of the VS (Minor et al, 1999). Paretic head-shaking nystagmus beating away from the side of the tumor Video 1. A characteristic finding seen in an INO is the slow adducting saccades as demonstrated in this video of a right INO. Additionally, the adduction deficit and contralateral abducting nystagmus is evident

Dizziness is the quintessential symptom presentation in all of clinical medicine. It can stem from a disturbance in nearly any system of the body. Patient descriptions of the symptom are often vague and inconsistent, so careful probing is essential. The physical examination is performed by observing the patient at rest and following simple movements or bedside tests Saccades can also be interrupted by other saccades in the opposite direction (back-to-back saccades) such as observed in voluntary nystagmus. These are truncated saccades. Slow saccades can result from muscle palsies and a variety of anomalies in premotor neurons (see Leigh and Zee, 1999 for a review) The treatment for saccade problems, like all ocular motor problems, assumes the child is in the best corrected visual acuity. The Hart Chart Decoding activity is also a good task. This task has a grid of letters on one sheet and themed (there are SpongeBob and Sports, and others)secret messages on another. Each letter in the message corresponds.

Saccades are everywhere: RHSC2 index has 33 entries under saccade! Saccade waveforms Appearance of saccadic waveforms: all saccade rotation-vs-time plots fall on the main sequence curve. See first figure of RHSC2 chpt 4. Note the perfect stopping of saccades. Is the quick phase of nystagmus a saccade? If it quacks like a duck, it's a duck.. Albinism. Albinism is the sensory disorder most frequently associated with INS. 25-26 Albinism includes a group of genetic disorders characterized by a congenital reduction of melanin pigment that can be limited to the eye (ocular albinism) but is more likely to involve the skin, hair, and eyes (oculocutaneous albinism [OCA]) (Table 2).Affected individuals show variable severity of skin and. Saccade eye movements happen when you look at a set object and your eyes move together to take the interesting points and make sense of them. Saccade movements can be both voluntary and. Nystagmus vs saccadic intrusion. Nystagmus vs saccades eye movement. Nystagmus vs spasmus nutans. Compare Search ( Please select at least 2 keywords ) Most Searched Keywords. 90714 denied by medicare 1 . Clayton mobile homes rogersville tn 2 . Greenville isd texas 3 . Drag times et by horsepower and weight 4 The horizontal asymmetry of upward vs. downward saccades did not change when the eyes were examined clinically in the left ear down, right ear down, and head down (pitch) positions. No torsional ocular deviation or nystagmus was observed in primary gaze or during the examination. FIG. 2

Differentiating among common central and peripheral acute

On nystagmus, saccades, and fixation

Saccadic Eye Movements. The ability to look at things is a familiar part of the process of seeing. Looking is achieved by orienting the eyes, that is to say directing their visual axes to point to a new location. Large orienting movements involve co-ordinated action of the eyes, head and body, but smaller movements, such as those made when. Basic Frenzel goggles do not track the eyes, produce tracings of the eye movements, or generate a report of any kind, although the clinician can observe nystagmus as the patient undergoes various procedures including smooth pursuits, random saccades and Dix Hallpike Either the curtain can turn around the child inducing optokinetic nystagmus, or the chair can rotate, inducing vestibulo-ocular nystagmus. Both have the effect of generating horizontal saccades. The pictures below, and the videos that follow, were all taken at the Eye Movement Laboratory at Great Ormond Street Hospital (videos kindly provided.

Types of Eye Movements [Saccades and Beyond] - iMotion

- Onset (Trauma, Episodic vs. Continuous) Symptoms - Conditions (recent cruise, recent illness, etc) - Current Complaints/Symptoms - Questionnaires (DHI, ABC, visual analog scale 3. Traditionaly divided into 2 types (upon clinical impression of the waveform): 1-pendular nystagmus :sinusoidal 2-jerk nystagmus: slow phase away from the object of regard (strength of nystagmus) by fast phase or saccadic (formed in the reticular formation)toward the target (direction of nystagmus) 6. Vor Gaze-evoked nystagmus is produced by the attempted maintenance of an extreme eye position. It is the most common form of nystagmus. Then, corrective saccade moves the eyes back toward the.

Types of Eye Movements and Their Functions - Neuroscience

CENTRAL VS. PERIPHERAL SIGNS OF VESTIBULAR DYSFUNCTION: PERIPHERAL • Direction-fixed nystagmus (Horiz.) • Nystagmus ↑ with fixation removed • Nystagmus ↑ with gazing in direction of the fast component (Alexander's Law) • Nystagmus ↑ after head shake test • Pursuits & Saccades Normal • Able to stand & walk with assistanc Nystagmus . A series of slow and fast phase of the rhythmical eye movement is called nystagmus. Several variations of direction including horizontal, vertical and/or rotational nystagmus can be observed. The direction of nystagmus is defined as the direction of fast phase. Physiological nystagmus describes the normal vestibulo-ocular reflex

Frontiers | Vestibular and Ocular Motor Properties in

A peripheral vestibular nystagmus can be suppressed in light with fixation, whereas central peripheral or other varieties of congenital or acquired nystagmus may not change or may even intensify in light with fixation. Participants will follow a moving target (laser point or light-emitting diode) for the saccade, smooth pursuit, and gaze testing A saccadic intrusion is initiated by a saccade that takes the eyes away from the target or intended gaze angle and is followed by either a return slow eye movement or a saccade. A saccadic oscillation is a repetitive series of saccadic intrusions. Nystagmus in Infancy There are several types of benign nystagmus usually seen in infancy Pathological nystagmus 2. Saccadic intrusions-The difference between them is the INITIAL movement. List the 2 main types of nystagmus and the main factor that differenitates them: slow/abnormal saccade (fast) Pathological Nystagmus has an initial _____-phase drift vs. Saccadic intrusion starts with an Optokinetic nystagmus (OKN) is a reflexive oscillation of the eyes induced by motion of the whole or, at least, a very large part of the visual field. The OKN response consists of an alternating sequence of following movements (slow phases) and fast resetting saccades (quick phases) Reverse optokinetic nystagmus (saccades in the same direction of optokinetic nystagmus strip movement and smooth pursuit in the opposite direction) is a finding seen only with congenital nystagmus. Additionally, an intact optokinetic nystagmus response can provide evidence of at least rudimentary visual function in infants or in individuals who.

Neuro-ophthalmology questions of the week: NOI16-Nystagmus

The saccades amplitude is the absolute difference between eye positions at the start and end of a fixational saccade in patients without nystagmus or quick phase in patients with nystagmus. The composite amplitude of fixational saccades and quick phases was measured by computing the square root of the sum of the squared values of horizontal and. Nystagmus has a quick phase and slow phase x Named for quick phase in relation to the patient If a peripheral lesion: x Unidirectional horizontal nystagmus x Quick phase beats towards the healthy ear x Nystagmus beats the same direction with lateral gaze If a central lesion: x Nystagmus changes direction; direction changing nystagmus x Horizontal and vertical If nystagmus present with. Eye tracking is the process of measuring either the point of gaze (where one is looking) or the motion of an eye relative to the head. An eye tracker is a device for measuring eye positions and eye movement.Eye trackers are used in research on the visual system, in psychology, in psycholinguistics, marketing, as an input device for human-computer interaction, and in product design saccades to flashed targets or after spontaneous gaze shifts in the dark. This property is then VOR produces compensatory eye movements during the slow phases of induced nystagmus with head perturbations. The reflex pathways are known to converge on an oculomotor integration process, located in the VN-Prepositus Hypoglossi (PH) complex used.

Signs and Symptoms of Central Vestibular Disorder

Nystagmus / OKN. Nystagmus refers to rapid backward and forward eye movements. The term can refer to a medical condition, in which case the back and forth movements can take many different forms. Typically there is a slow and fast phase. The slow phase can be equated to smooth pursuit, and the fast phase to a saccade accurately, brief catch-up saccades will be inter-posed during the eye movement and the eyes will be seen to jerk as they follow the target. For impaired individuals, catch-up saccades are read-ily evident for target speeds of about 30 deg/sec. At high levels of impairment, an individual can even lose the ability to make saccades and, thus

Nystagmus more likely to be exacerbated post horizontal headshake - horizontal nystagmus Nystagmus post-headshake vertical . Pursuit tracking and saccade performance normal (or age dependent) Likely to have abnormal performance on pursuit and/or saccades If sudden onset, can stand and walk with assistanc 1. Is there central nystagmus? First we should talk about nystagmus, the n in HINTS. These are the quick saccade movements that occur in patients with vestibular issues. There is a fast followed by slow movement and the nystagmus is named for the direction of the fast component. No nystagmus is considered normal Fixational saccades and quick phases of nystagmus were identified using an unsupervised clustering method 35. Drifts and slow phases were defined as epochs between fixational saccades and quick. Central Finding: Absence of saccade (no large beats of nystagmus as the eyes catch up to re-fixate on examiner's nose) is concerning. Direction-changing nystagmus in eccentric gaze (Nystagmus) Assess for a presence of nystagmus Eye movements are frequently considered diagnostic markers indicating involvement of the cerebellum. Impaired amplitude of saccades (saccade dysmetria), impaired gaze holding function (horizontal or downbeat nystagmus), and interrupted (choppy) pursuit are typically considered hallmarks of cerebellar disorders. While saccade dysmetria is a frequently considered abnormality, the velocity of.

Direction fixed nystagmus-horizontal (opposite side of affected ear) Nystagmus worse in direction of fast component Abnormal VOR-head thrust Nystagmus worse after horizontal head shake test Pursuit tracking and saccade performance normal Can stand and walk with assistance (can coordinate LE's) Vestibular Hypofunction Alexander's La Test: Catch up saccades on one side, but not the other indicates peripheral vestibular lesion on that side; Nystagmus (N) Nystagmus changes direction on eccentric gaze → central lesion; Skew deviation (TS) Eyes are vertically misaligned because of imbalance of vestibular tone → central lesion; Alternately cover each eye to test for realignmen

Vertigo: A hint on the HiNTs exam — NUEM Blo

fovea. Saccades are said to be ballistic because once it starts, it will not stop until it reaches the target location. Even if the target location moves or disappears, the eyes would immediately find a new target and saccade to that point. Saccades are also very quick. A single saccade only takes about 150-200 ms to plan and execute. Th Saccades Definition: Saccadic movement, or more commonly known as saccades, is the ability of the eyes to move in synchrony from point A to point B rapidly WITHOUT deviating from the path. Typically, we look for these patterns to be established in left/right and top/bottom patterns as they are the easiest to identify Nystagmus -Nulling head-eye positions -Convergence null Ocular Motor Apraxia (OMA) -Lack of horizontal saccades -Head thrusts to move eyes to target, overshoot and correction to fixate . Cortical post-chiasm to V1 (striate or occipital) DL Mayer 2.28.10 Cerebra - Saccade, tracking, optokinetic • Tests of gaze stabilization (with fixation and without fixation) - Gaze/spontaneous nystagmus, static position • Tests of vestibular function - Caloric • Tests for specific etiologies - Dix-Hallpike maneuver (dynamic positioning), pressure (fistula A comparison between saccades and quick phases of vestibular nystagmus in the cat. Guitton D , Mandl G Vision Res , 20(10):865-873, 01 Jan 198

Nystagmus and Saccadic Intrusions and Oscillations Ento Ke

b. Saccadic saccades c. Spontaneous nystagmus d. Gaze evoked nystagmus 5. Hallpike-Dix test a. If have positional dizziness 6. Musculoskeletal exam 7. Sensory exam 8. Tests and measures a. Depends on functional level b. Objective and reliable c. e.g. - Berg, DGI, TUG 9. Coordination tests a. Rapid alternating movements, finger to nose 10. Consistent saccades on repetition of test directions. Nystagmus: quick phase AWAY from lesion side Central End point Nystagmus (normal response) During maintenance of an extreme eye position. Head fixed. Eyes follow my finger and then held at the end point. (all 4 directions). 1-2 beats is normal. Gaze evoked Nystagmus

Recommended Reading - Treatment of Nystagmus and Saccadic

It allows an assessment of the conjugacy of pursuit eye movements (slow phase of nystagmus) and saccades (fast phase of nystagmus). To test fast, saccadic eye movements, the patient is asked to shift the gaze quickly between different earth-fixed targets (e.g. the examiner's nose and the tip of a pen). This is usually assessed in both the. Optokinetic nystagmus is for stabilising the pictures we see when we are observing moving objects for example if we are rotating on an office chair. If we wear a mask while rotating however, the optokinetic nystagmus will not occur since we don't see. but with closed eyes the saccades are still there. Edit: The two senses can also be in.

Neuro-ophthalmic Complications in Multiple SclerosisVisual Fixation & Gaze Stability at Gettysburg CollegeCentral vertigoEyeRoundsONDERZOEKSTECHNIEKEN - Coggle Diagram

Saccades - overshoots (hypermetric) Saccades - undershoots (hypometric) Saccadic slowing The eyes can accurately reach the target but do so much slower than normal. This can be symmetric or asymmetric. CALIBRATION errors and drug use must be ruled out for accurate interpretation. Caution! zSuperimposed gaze nystagmus zSuperimposed. represent a true nystagmus, but rather a series of saccades when the patient looks laterally. The abducting eye saccades may be an adaptive attempt by the brain to correct for the hypometric saccades of the weak medial rectus muscle.3 Demyelination and brainstem stroke are the most causes of internuclear ophthalmoplegia Vertical nystagmus may be either upbeating or downbeating. When present in the straight-ahead position of gaze (i.e. the primary position) it is referred to as 'upbeat nystagmus' (UBN) or 'downbeat nystagmus' (DBN) (Leigh and Zee, 1999).DBN is usually greater on looking laterally or in downgaze, whereas UBN often increases on upgaze