Eye Nystagmus Research Articles

Involvement of ON and OFF retinal channels in the eye and head horizontal optokinetic nystagmus of the frog

The specific role of ON and OFF retinal information channels in the generation of the horizontal optokinetic nystagmus (OKN) of the frog was studied. Coil recordings of monocular eye and head OKN were obtained before and after intravitreal injection of two drugs that block either ON or OFF channels. The intravitreal injection of 2-amino-4-phosphonobutyrate (APB), a glutamate analog that selectively blocks the ON retinal channel, strongly reduced or even cancelled the monocular OKN of the head and of the eye. The intravitreal injection of another glutamate analog, the cis-2,3-piperidine dicarboxylic acid (PDA) that especially blocks the OFF retinal channel, did not affect the gain velocity of the slow phase of both the horizontal monocular head and eye OKN, for low stimulus velocities. Our results suggest that the retinal ON information channel, but not the OFF channel, is involved in the generation of the slow phase of the OKN of the frog, at least at low drum velocities.

Congenital adduction palsy and synergistic divergence: a clinical and electro-oculographic study.

We studied two patients with a peculiar congenital disturbance of ocular motility in which the horizontal movements of the left eye were always opposite the normal expected direction. The common features were: (1) congenital monocular adduction palsy and exotropia of the left eye; (2) simultaneous abduction of both eyes (divergence) on attempted dextroversion; (3) ocular torticollis, head turned to the right; and (4) inverse nystagmus of the left eye, occurring spontaneously as well as during optokinetic and vestibular testing. Clinical and electrooculographic findings suggested a close relationship to Duane's retraction syndrome and supported the concept that innervational mechanisms were responsible for the phenomenon.

Chapter 16 Open-loop and closed-loop optokinetic nystagmus in Squirrel monkeys (Saimiri sciureus) and in man

Horizontal optokinetic nystagmus (OKN) was measured in 3 normal Squirrel monkeys by means of the electromagnetic search coil technique. Binocular and monocular stimulation of each eye to the left and right by moving vertical stripe patterns of 2.37 or 15 degree period were applied at angular velocities of 0.5 to 400 deg/s. After measurement of horizontal OKN under normal conditions, open-loop OKN gain was determined by monocular stimulation of an eyeball immobilized by means of retrobulbar injections of 11 units botulinum toxin (BoTx type A) and compared with the pre-injection data or with monocular stimulation of the other eye, which remained mobile. In normal Squirrel monkeys gain of optokinetic nystagmus reached values between 0.8 and 0.97 at angular velocities below 1.5 deg/s. Gain under these conditions was related to stimulus angular velocities Vs, i.e. Ge = Ve/Vs. A slightly higher gain was found for binocular than for monocular stimulation. No significant differences were found in OKN when monocular stimulation in the naso-temporal and in the temporo-nasal direction was applied. The upper cut-off angular velocity (-3 dB-point) reached values of 180-230 deg/s, significantly above those observed in man under similar stimulus conditions. Monocular optokinetic stimulation of an immobilized eye led to vigorous optokinetic nystagmus and OKAN of the other eye, whereby maximum gain (Gi = Ve/Vr) was found to be between 20 and 30 at lower retinal stimulus velocities (2-5 deg/s). Gain was related to retinal stimulus velocity Vr. Increase in Vr above 10 deg/s led to a decrease in gain with a slope of about 20 dB per decade. Measurement of gain of closed-loop OKN related to retinal stimulus velocity Vr (which was determined by the difference between Vs and Ve) led to a similar dependence of OKN as in closed-loop stimulus conditions. Differences in sensitivity between the temporal and the nasal visual hemifield stimulation evoking horizontal open-loop OKN are described. Directional selectivity appeared in these experiments. Open-loop OKN data from a human subject are reported. With highly attentive horizontal optokinetic gaze nystagmus, Ve depended on the duration of the pursuit phases of OKN. Ve accelerated with the duration of the individual slow phase of OKN and was reset by each backward saccade (of the covered mobile eye). OKN gain was considerably smaller when the subject intentionally pursued as many stripes as possible of the 1.15 degree period stripe pattern (gain related to Vr about 1.5-3).(ABSTRACT TRUNCATED AT 400 WORDS)

Detection of nystagmus eye movements using a recursive digital filter.

A method based on a recursive digital filter is presented that recognizes minima and maxima of nystagmus. The method does not require user assistance. However, it takes into account the type and changes of input by adapting itself to these. The method has been tested with nystagmus data. If the algorithm is slightly modified, it can detect other eye movements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Case 24-1986

Presentation of CaseA 65-year-old woman was admitted to the hospital because of a cough and bilateral pulmonary infiltrates.She was well until six years earlier, when she began to have scalp pain and tenderness that radiated to the jaw and gums. A physician prescribed an antibiotic, and her symptoms subsided after one month. One month later diplopia developed abruptly, and she was admitted to the hospital, where examination showed a right internuclear ophthalmoplegia, with mild nystagmus of the left eye on leftward and upward gaze, and slight unsteadiness of gait. There was questionable tenderness over the left temporal artery, . . .

Tonic cervical influences on eye nystagmus following hemilabyrinthectomy: immediate and plastic effects

In intact guinea pigs a passive horizontal rotation of the body about the fixed head induces compensatory ocular movements (cervico-ocular reflex). When the static neck deviation is maintained, a significant ocular displacement is observed. In acutely hemilabyrinthectomized animals, static body deviation towards the lesion side tonically alters eyenystagmus. It affects slow phase eye velocity and quick phase amplitude and frequency causing the eye to reach a less eccentric orbital position. Apart from such immediate influences, a plastic effect on eye nystagmus abatement is induced. In the animals restrained with no body-on-head deviation, abatement of nystagmus is delayed with respect to the animals restrained with 35° body deviation towards the lesion side. Thus the head position signal is not only a contributing factor for the correction of postural deficits but also influences the time course of the ocular balancing process following unilateral vestibular damage.

The horizontal optokinetic nystagmus in the cat.

Horizontal optokinetic eye nystagmus (OKN) and after nystagmus (OKAN) were recorded in the alert cat (head restrained) in response to velocity steps and sinusoidal optokinetic stimuli. A strong dependency of OKN performance on stimulus pattern was found: responses were most regular and gain was high over a large range of stimulus velocities when the stimulus consisted of a high-contrast random dot pattern. Following velocity steps, OKN showed a small amplitude fast rise in slow phase velocity (SPV) which was followed by a slow build-up to steady state. The amplitude of the initial jump in SPV increased with stimulus amplitude up to 30 degrees/s and saturated afterwards. The plateau level of initial SPV ranged from 5 to 15 degrees/s. The slow build-up of SPV showed non-linearities, i.e. the time to steady state increased with stimulus amplitude and the slow rise of SPV was irregular. In most animals steady state SPV showed no signs of response saturation for step amplitudes up to 60-80 degrees/s or more. The open-loop gain (steady state SPV/retinal slip velocity) depended on retinal slip velocity and decreased from 46 at 0.5 degrees/s to 0.4 at about 60 degrees/s. OKAN I and II were consistently observed and occasionally OKAN III was noted. OKAN I durations (mean 13.8 +/- 5.1 s) and OKAN II amplitudes were independent of stimulus magnitude. Initial SPV of OKAN I was typically the same as that of OKN, i.e. no fast fall was observed. Cessation of pattern rotation in light, however, produced a fast initial decay of SPV. A least square fitting of OKAN time course was performed with various time functions. The SPV of OKAN I and II was best fitted with a damped sine wave, indicating that cat optokinetic system behaves like a second order underdamped system. Sinusoidal stimuli produced strong response non-linearities. At a given frequency gain decreased with increasing stimulus amplitudes. Gain correlated best with stimulus acceleration. In addition, strong stimuli produced characteristic response distortions. In the visual-vestibular conflict situation vectorial summation of VOR and OKN was observed only with small stimuli.

Initial, rapid phase of recovery from unilateral vestibular lesion in rat not dependent on survival of central portion of vestibular nerve

The behavioral effects of vestibular endorgan lesions were compared with those of vestibular ganglion lesions in the albino rat. No differences in head tilt angle or spontaneous eye nystagmus beat frequency were noted between the two groups during the first 36 h after the lesion was made. Of rats studied beyond 36 h, 2/7 with lesions restricted to the endorgans and 2/3 with ganglion lesions showed pronounced secondary increases in head tilt and tonic eye deviation, but not eye nystagmus. Single units were recorded in the ganglion acutely, as well as 1, 2, and 14 days after an endorgan lesion was made. Practically no resting activity could be recorded in the ganglion acutely (2–7 h) after endorgan damage, and the resting activity at subsequent times was slight. It is concluded that an intact vestibular ganglion isolated from the sensory periphery is of no functional significance during the first 36 h, when the largest decreases in magnitude of the behavioral signs of unilateral labyrinthectomy occur in the rat. A slight significance at later times is not ruled out.

Eye velocity responsiveness and its proprioceptive component in the floccular Purkinje cells of the alert pigmented rabbit.

Eye velocity responsiveness of floccular Purkinje cells was studied in alert, pigmented rabbits. Conjugate horizontal eye nystagmus was elicited by application of electric pulse trains (10-50 microA, 30 c/s) to the optic tract through chronically implanted electrodes. Purkinje cells were sampled with an extracellular microelectrode from the flocculus, and their involvement in different oculomotor functions was specified by electrical stimulation at their recording sites. At those sites where abduction of the ipsilateral eye was elicited, the discharge frequency of simple spikes usually increased during slow eye movement to the ipsilateral side and decreased during eye movement to the contralateral side in nystagmus and after-nystagmus. Within a limited range, the discharge frequency increased linearly with eye velocity, at an average rate of 1.6 impulse s-1/degree s-1. An opposite directional specificity (decrease in ipsilateral and increase in contralateral eye movement) and directional non-specificity were common at other floccular sites where local stimulation elicited downward or no eye movement. Retrobulbar anesthesia of proprioceptive afferents from one eye reduced the eye velocity responsiveness of Purkinje cells in the ipsilateral flocculus by 31%, but did not affect their responsiveness in the contralateral flocculus. These observations indicate that eye velocity input to the rabbit flocculus arises partly from peripheral receptors but mainly from the central oculomotor system, and that responsiveness of Purkinje cells to the input is organized specifically according to their functional involvement.

Correlation between the Cervical Proprioceptors and the Otolith with regard to the Development of Nystagmus of Cervical Origin

To understand better the correlation between the cervical proprioceptors and the otolith, in the development of eye nystagmus of cervical origin, the following two series of experiments were carried out using rabbits.Experiment A: Rabbits with healthy ears were placed in the following five postures and eye deviation and/or eye nystagmus induced in these postures were recorded from the right eye using electronystagmograph (ENG) and the electromyographs (EMG's) of the bilateral deep neck muscles were also recorded. The 1st posture: a piece of cloth is wrapped around the trunk of a rabbit to suspended it in the air so that its four limbs do not touch the ground. The 2nd posture: the animal's head is in the normal position and the trunk and limbs are rotated 90 degrees counterclockwise around the longitudinal axis of the body. The 3rd posture: the animal's trunk and limbs are in the normal position and the head is then rotated 90 degrees clockwise around the longitudinal axis of the body. The 4th posture: the animal's whole body is laid down on the left side. The 5th posture: the animal's head is in the normal position and the trunk and limbs are then rotated above 90 degrees counterclockwise around the longitudinal axis of the body. In experiment A, the following facts were noted.(1) In the 1st posture, neither asymmetry in the activity of the bilateral deep neck muscles nor eye movement was observed.(2) In the 2nd posture, only eye deviation was induced together with increased activity of the unilateral deep neck muscles, whereas in the 5th posture, eye nystagmus was elicited.(3) In the 4th posture, deviation of the eyes, i. e., compensatory eye deviation of otolithic origin developed together with increased activity of the unilateral deep neck muscles.(4) In the 3rd posture, development of eye nystagmus was the most conspicuous, together with a marked increase in the activity of the unilateral deep neck muscles.From these results, we conclude the following.First, the cervical proprioceptors can induce nystagmic responses, whereas the otolith induces only eye deviation. Second, the otolith can play a major role in the enhancement of nystagmus of cervical proprioceptive origin.Experiment B: Rabbits with healthy ears are placed in the following four postures and eye deviation and/or eye nystagmus induced in these postures are recorded from the right eye using ENG. The four postures referred to herein are as follows. The 1st posture: the same posture as the 1st posture described in experiment A. The 2nd posture, the animal's whole body is rotated counterclockwise on the sagittal plane with its nose up. The 3rd posture, the animal's head is in the normal position and the trunk and limbs are then rotated clockwise on the sagittal plane with its tail up. The 4th posture, the animal's trunk and limbs are in the normal position and the head is then rotated counterclockwise on the sagittal plane.In experiment B, the following facts were noted.(1) In the 2nd posture, deviation of the eyes, i. e., compensatory eye deviation of otolithic origin developed around the bitemporal axis of the body.(2) In the 3rd posture, rotatory eye nystagmus developed around the bitemporal axis of the body. The nystagmus thus induced was small in amplitude and low in frequency.(3) In the 4th posture, rotatory eye nystagmus developed around the bitemporal axis of the body. The nystagmus thus induced became larger in amplitude and frequency when compared to that of the 3rd posture.On the basis of these results, we conclude that the otolith does play an important role in the enhancement of nystagmic responses of cervical proprioceptive origin.

Effect of amphetamine on optokinetically evoked head and eye movements in the squirrel monkey.

The effect of amphetamine sulfate injection on head and eye movements evoked by optokinetic stimulus was studied in squirrel monkeys. No change was found in the gain of optokinetic-oculomotor and optokinetic-caputomotor functions, even after the maximum dose (0.5 mg/kg) of amphetamine. Also, no change in eye-head coordination was found. However, amphetamine facilitated the frequency of head nystagmus, whereas that of eye nystagmus did not change. When the poststimulus responses were studied in the dark, both nystagmoid head movement and optokinetic after eye nystagmus showed first phase and second phase. A different effect was found in the duration of these two phases suggesting the existence of distinct generators. Moreover, the synchronized onsets of head and eye nystagmus in both phases, and synchronized occurrence of quick phases indicated the existence of shared neural circuitry between head and eye movements.

Abnormal eye movement and nystagmus in the case of cerebellar lesion.

Abnormal eye movement and nystagmus in the case of cerebellar lesion.

Illuminance and recording of eye movements by electro-oculography.

The fluctuation of the d.c. potential of the eye following changes in the ambient level of illuminance is well recognised in the field of ophthalmology. However, the influence of this factor in the recording of eye movements in the oto-neurological clinic has been little investigated. In this study the variation in the d.c. potential was measured for fixed periods of time after subjects entered a clinic environment of known illuminance and after entering the dark. In the short term (3-4 min), the variation in d.c. potential was less than 20% in the 22 subjects tested. Suggestions are made to minimise these fluctuations in the recording of nystagmus and other eye movements.

Relationship between cerebral nystagmogenic area and spinal cord

The effect of section of the spinal cord upon the cerebral nystagmogenic area was investigated in rabbits. Cervical transection was found to result in an increase of excitability of such area, which is demonstrated by lowering of the threshold for cerebral eye nystagmus, whereas dorsal spinal transection does not affect the cerebral nystagmogenic area. Moreover,it was found that stimulation of the proximal stump of the spinal cord, at level of the dorsal quadrants, depresses the excitability of the cerebral nystagmogenic area, while ventral quadrants stimulation has a facilitating effect on the CNA. Modification of the excitability of the cerebral nystagmogenic area was also studied recording NPPs (Non-Primary Potentials) and unitary responses to photic stimulation prior to and after cervical transection as well as following dorsal and ventral quadrants stimulation. The Authors suggest that since the nystagmogenic area is located in the perivisual fields it receives visual and sensitive afferent impulses from the upper part of the body and it, in turn, projects onto the oculomotor nuclei, so that it could be considered as an integrator center for extrinsic musculature of the eye.

Algorithms for the clinical analysis of nystagmus eye movements.

Two algorithms used in the clinical analysis of nystagmus are described. Their development was necessitated by the greater complexity of the nystagmus waveforms in response to system identification types of vestibular and optokinetic stimuli as compued to the less complex response to a step input. Practical considerations for clinical application also influenced their development. The first algorithm converts nystagmus data into a regulary sampled estimate of slow phase velocity (SPV), an important feature of the signal. It uses a new set of fast phase detection conditions which allow for automatic processing of reversals in nystagmus direction and for wide variability for clinical data. The second algorithm detects noise induced spikes in this SPV estimate using an adaptive criterion based upon a measure of the overall noisiness of the data compared to the stimulus.

Eye-head coordination and lateral canal block in squirrel monkeys.

Eye and head nystagmus during horizontal optokinetic stimulation was analyzed in squirrel monkeys. Slow phase speed of coupled head and eye nystagmus showed highly significant negative correlations in normal subjects; correlation coefficients were -0.81 at 60 degrees/sec and -0.72 at 100 degree/sec stimuli. Bilateral semicircular canal block resulted in a reduction of the negative correlation. The postoperative reduction of the correlation coefficient value ranged from 0.17-0.28 (significant at P less than 0.01 level) at 60 degrees/sec stimulus and 0.06-0.13 (non significant) of 100 degrees/sec stimulus. Gaze speed was calculated by summing slow phase speeds of coupled head and eye nystagmus. Mean error of gaze in normal subjects was 1.5% at 60 degrees/sec stimulus and 7.8% at 100 degrees/sec stimulus. Mean gaze speed showed an overshoot (8% at 60 degrees/sec stimulus and 6.5% at 100 degrees/sec stimulus) in the tree to four weeks postoperative period; however, this subsided two to three months after the operation. Measurement of head-turning performance (in yaw plane) in humans may provide a clinically useful index for the assessment of certain types of vestibular function.

Role of vestibular nuclei in ‘optic’ nystagmus

Horizontal eye nystagmus beating towards the stimulated side (‘optic’ nystagmus) was evoked in 25 guinea pigs by stimulating an optic nerve. The complete ablation of the vestibular nuclear complex abolished this nystagmus. In a second group of 15 animals, the behaviour of 63 vestibular neurons identified electrophysiologically was analyzed during eye nystagmus; most of these neurons responded with a tonic increase in discharge rate to stimulation of the optic nerves. Units sensitive to the direction of optic and labyrinthine nystagmus were also identified.

Eye-head coordination during optokinetic stimulation in squirrel monkeys.

Head and eye movements in the yaw plane were recorded during and after optokinetic stimulation in squirrel monkeys. 1) Phasic or tonic head deviations to the side of the ocular quick phase occurred in 94% of total recordings (n = 50) during the perstimulus period, and in 75% of recordings (n = 49) during the poststimulus period. Magnitude of mean head deviation was significantly different between perstimulus and poststimulus periods. 2) Head nystagmus associated with eye nystagmus was consistently observed in seven of nine squirrel monkeys during optokinetic stimulation. Squirrel monkeys are thereby less prone to display head nystagmus than either guinea pigs, pigeons or chickens. 3) Slow phase speeds of coupled head and eye nystagmus were subjected to statistical analysis. A highly significant negative correlation was found between slow phase head and eye speeds. The correlation coefficient was - 0.81 at 60 degrees / sec stimulus (n = 119) and -0.72 at 100 degrees / sec stimulus (n = 131). The gaze speed, calculated by summing the head and eye speeds, was 59.1 plus or minus 6.8 / sec at 60 degrees / sec and 92.2 plus or minus 11.4 at 100 degrees / sec stimulus. There was no significant difference between the gaze speed in a free head condition and the eye speed when the head was fixed.

Pathophysiology of inner ear dysfunction in the squirrel monkey in rapid decompression.

More than 90 squirrel monkeys with bilateral myringotomies (a small hole in each ear drum) were rapidly decompressed in a hyperbaric chamber according to a special diving profile in which 35% of attempts produced disorders ("hits") confined to the inner ear. Monkeys receiving inner ear hits (as determined by the sudden onset of vigorous head or eye nystagmus during decompression) were tested and killed at times ranging from 1 h to more than 12 mo following the dive. Histologically, in monkeys killed 1 mo or less after the hit, hemorrhage and/or a deep purple-staining precipitated material were frequently found in the otic fluid spaces. In those monkeys killed more than 1 mo after a hit, ectopic new bone growth in the arms of the semicircular canals was a common sequela. New bone growth never appeared in the cochlea. In unaffected ears, and in both ears of control animals, the precipitated material was somewhat less than in ears damaged by decompression; and, furthermore, new bone growth did not occur. Behaviorally, the hit monkeys showed vestibular deficits that were consistent with the structural damage revealed by histology.

Reflex control of acute postural asymmetry and compensatory symmetry after a unilateral vestibular lesion

The roles of certain multisensory tonic postural reflexes in determining acute postural asymmetry and compensatory symmetry were studied in guinea-pigs after a unilateral vestibular neurectomy. The frequency of uncompensated eye nystagmus is modulated by neck proprioception, limb afferent blockade and orientation to gravity. The effect of orientation to gravity upon the frequency of nystagmus is seen for 3–4 days and the neck proprioceptive effect for 2–3 days after the unilateral neurectomy. Neck and trunk asymmetries induced by vestibular input are reversed in direction when the animal is turned upside down and is forced to press its feet against a surface. This reaction is called a Head Deviation Reversal. Restraint of the position of the head during compensation does not alter the compensation of the frequency of eye nystagmus but the rate of compensation of lateral head deviation is altered depending on the position of head restraint. Compensatory symmetry is disrupted by limb blockades and by lesions to the spinal lateral and dorso- and ventrolateral funiculi but not to the dorsal columns. Lesions just above C-1 produce severe body asymmetries in ‘compensated’ animals that last for several days, and the direction of body and eye asymmetries depends on the side of the C-1 lesion. In contrast, lumbar lesions produce milder asymmetries that last for a few hours and that are in the original uncompensated direction regardless of the side of the spinal lesion. It is concluded that the integrative operations that occur during vestibular eye nystagmus and lateral head deviation are under significant reflexive tonic influences from the spinal cord and the otolithic end organs. Spinal influences are, however, a very minor factor in the plasticity mechanisms that underlie eye nystagmus compensation. In contrast the compensation mechanisms for lateral head deviation appear to involve influences from the lower and upper spinal cord. The achievement of compensatory eye and body postural symmetries apparently involves an alteration of the functional relationships between the spinal circuits and the suprasegmental postural circuitry. This compensatory relationship is more pronounced for upper cervical than for lower spinal influences, and does not involve the dorsal column system.