Nystagmus Amplitude Research Articles

Surgical management of nystagmus

All nystagmus degrades visual acuity by reducing the stability of fixation and lessening foveation time. In addition, adults with acquired nystagmus may complain of oscillopsia, a subjective impression of movement of the perceived world. Surgery may be performed for congenital nystagmus (CN), for latent or manifest-latent nystagmus (LN, MLN) or for acquired nystagmus. Nystagmus surgery aims to reduce the amplitude of nystagmus with either improvement of visual acuity or a reduction of a bothersome head posture. The commonest reason for patients' seeking surgical treatment is to allow them to acquire a driving licence. Regrettably, this is frequently not possible.

Menstrual cycle effects on postural stability but not optokinetic function

We investigated the effects of the menstrual cycle on visual-vestibular interaction by measuring optokinetic function and postural stability at different phases of the cycle. Menstrual cycle phase had no significant effect on gaze-holding, optokinetic nystagmus slow phase velocity, amplitude or frequency, circularvection latency or optokinetic afternystagmus frequency, amplitude or duration. While menstrual cycle phase had no significant effect on anterior-posterior sway, it did significantly affect lateral sway ( P<0.001), with sway on day 5 significantly greater than on days 12 and 21 ( P<0.05 and 0.01, respectively), and sway on day 25 significantly greater than that on day 21 ( P<0.05).

Image analysis of quick phase eye movements in nystagmus with high-speed video system.

There are several methods of measuring horizontal, vertical and torsional nystagmus for the diagnosis of vertigo. Using Frentzel glasses, electronystagmography (ENG) and video-oculography (VOG) are common methods for observing nystagmus. In this study, a high-speed video camera is used to analyse high-speed eye movements, including three components of nystagmus, in order to monitor precisely the amplitude and velocity of the quick phase of nystagmus. To confirm the accuracy of the analysis, images of optokinetic nystagmus (OKN) evoked by a stimulating device were analysed. We obtained a high linearity with regard to the relation between the horizontal nystagmus amplitude detected with the high-speed video system and ENG (R2= 0.99). On comparison of the maximum velocities detected with 30Hz and with 250 Hz at each amplitude, the velocities calculated at 30Hz were smaller than those calculated at 250 Hz. At an amplitude of 5 degrees , the 30 Hz velocity decreased by 50%, while a decrease of 35% was observed at 15 degrees. The vertical nystagmus data obtained using high-speed VOG was different in appearance to that obtained using ENG. The torsional component of nystagmus was also measured, and was recorded in the form of a large number of sampling points.

Reduction of congenital nystagmus amplitude with auditory biofeedback

Purpose: Treatment options for congenital nystagmus without null position are limited. The purpose of this study was to evaluate the role of auditory biofeedback in controlling congenital nystagmus. Methods: Ten patients with congenital nystagmus without null position underwent 6 sessions (twice a week for 3 weeks) of auditory biofeedback. Each half-hour session had simultaneous electronystagmographic recording done during the session. Results: The patients could reduce the nystagmus during the treatment sessions. Mean amplitude (degrees) of nystagmus was reduced from 6.28 ± 4.94 to 3.05 ± 2.48 (P = .028) and mean intensity (amplitude × frequency) was reduced from 33.37 ± 22.84 to 13.35 ± 7.99 (P = .0174), but the mean frequency change was not significant, from 5.8 ± 1.05 to 4.98 ± 1.35 (P = .148). The mean amplitude and mean intensity decreased by 51% and 60%, respectively. After completion of the session, although a subjective improvement was reported, the patient's binocular visual acuity on Snellen's charts and contrast sensitivity did not show any significant change. Also no sustained benefit was noted because the electronystagmographic recordings reverted to baseline after the auditory stimulus for biofeedback was discontinued. Conclusion: Simultaneous electronystagmographic recording shows significant reduction of nystagmus amplitude and intensity because of auditory biofeedback only during the treatment session. The beneficial effect does not persist after the auditory stimulus is discontinued. No objective effect on visual acuity and contrast sensitivity was noted after the therapy. (J AAPOS 2000;4:287-90)

Effects of galvanic vestibular stimulation on otolithic and semicircular canal eye movements and perceived vertical

Objective: The aim of this study was to determine the otolithic and semicircular canal effects of galvanic vestibular stimulation with increasing current strengths on eye movements and the perception of verticality. Methods: We measured (1) 3-dimensional eye movements, (2) subjective tilt of the peripheral visual field, and (3) subjective tilt of a central vertical line in 12 healthy subjects during galvanic vestibular stimulation. A rectangular, unipolar binaural electric current was applied to each subject's mastoid. Results: Anodal stimulation of the right mastoid led to an ipsiversive tonic ocular torsion of up to 5.4°, to a contralateral tilt of both the peripheral visual field (1–9°), and a central vertical line (0.5–6.2°) increasing in amplitude with increasing current strengths applied. This reflects otolith stimulation. In most subjects, current strengths of 3 mA or more elicited a slight (horizontal-) torsional nystagmus (amplitude 1–2°) that was superimposed on static torsion. This reflects horizontal and vertical semicircular canal stimulation. A correlation was found in the amount of the 3 measured parameters and the strength of the applied current. Conclusions: Thus, galvanic vestibular stimulation at low current intensities (1– 3 mA) preferably excites otolith responses, which increase with increasing current intensity. With higher current intensity above 3 mA, additional semicircular canal responses are elicited in the form of horizontal-rotatory nystagmus superimposed on static torsional deviations. The lack of a vertical deviation and nystagmus can be explained by the counterdirected vertical components of the anterior and posterior semicircular canal.

Eye movement abnormalities correlate with genotype in autosomal dominant cerebellar ataxia type I.

We compared horizontal eye movements (visually guided saccades, antisaccades, and smooth pursuit) in control subjects (n = 14) and patients with three forms of autosomal dominant cerebellar ataxias type I: spinocerebellar ataxias 1 and 2 (SCA1, n = 11; SCA2, n = 10) and SCA3/Machado-Joseph disease (MJD) (n = 16). In SCA1, saccade amplitude was significantly increased, resulting in hypermetria. The smooth pursuit gain was decreased. In SCA2, saccade velocity was markedly decreased. The percentage of errors in antisaccades was greatly increased and was significantly correlated with age at disease onset. In addition, a correlation between smooth pursuit gain and the number of trinucleotide repeats was found. In SCA3, gaze-evoked nystagmus was often present as was saccade hypometria and smooth pursuit gain was markedly decreased. Three major criteria, saccade amplitude, saccade velocity, and presence of gaze-evoked nystagmus, permitted the correct assignment of 90% of the SCA1, 90% of the SCA2, and 93% of the patients with SCA3 to their genetically confirmed patient group and, therefore, may help orient diagnoses of SCA1, SCA2, and SCA3 at early clinical stages of the diseases.

The Association of Strabismus, Amblyopia, and Refractive Errors in Spasmus Nutans

Spasmus nutans is a condition that includes asymmetric nystagmus and occurs during the amblyogenic period. Because specific alterations in early visual experience are known to be associated with changes in visual development, relations between spasmus nutans and abnormal visual sequelae were examined. The records of 18 patients with spasmus nutans were reviewed retrospectively. The incidence of strabismus, amblyopia, anisometropia, and astigmatism was compared with published age-matched control subjects. There was a significantly higher incidence of strabismus (10 of 18) and amblyopia (8 of 18) of the eye with the greater amplitude of nystagmus. No correlation of refractive error with lateralization of nystagmus could be established. Twelve of 18 patients required spectacles for improvement in visual acuity and for treatment of amblyopia. Best-corrected visual acuity averaged 1.20 Snellen lines poorer than age-adjusted normative values; however, loss of visual acuity was, in most cases, symmetric and not related to lateralization of nystagmus. Early detection and treatment of anticipated abnormal visual issues in patients with spasmus nutans will optimize visual outcomes.

非減衰振子様回転刺激を用いた垂直半規管機能の評価 健康成人と高齢者との比較

Pendular rotation test in a head-tilted position was performed with a stimulus mode; amplitude=360 degrees, frequency=0.1 Hz, and maximal speed=114 deg/sec. The subject's head was tilted 60 degrees backward from the upright position, and then rotated 45 degrees either to the left or right. Using this test procedure, it was possible to evaluate the excitability of vertical semicircular canals, using infra-red CCD camera and a personal computer to analyze nystagmus.There were no significant differences in the maximal slow phase eye velocity (SPEV) or in the maximal amplitude of vertical nystagmus from the anterior or posterior semicircular canal in normal adult subjects. However, a significant difference in the maximal SPEV of vertical nystagmus was found between the anterior semicircular canal and posterior semicircular canal in elderly subjects over 70 years old. Excitability of the posterior semicircular canal was lower than that of the anterior semicircular canal in these elderly subjects. Moreover, excitability of the posterior semicircular canal in elderly persons was lower than that in normal non-elderly subjects.

Optokinetic Nystagmus Elicited by a Random Dot Pattern and a Wide Interval Stripe Pattern in Normal Subjects

In optokinetic stimulus in practical living conditions, not only the central fovea but also the peripheral retina are strongly stimulated. In order to investigate the influence of this stimulus on the peripheral retina in optokinetic nystagmus (OKN), we tested OKN elicited by a pattern of numerous random dots (ROKN) in 30 normal subjects and compared the results with those of OKN elicited by a wide interval stripe pattern. The most significant difference between the two response patterns was the correlation between slow phase velocity and slow and fast phase amplitude. In ROKN, the nystagmus amplitude was highly correlated with slow phase velocity. On the other hand, in SOKN there were two types of correlation between slow phase velocity and nystagmus amplitude. One indicated low correlation, which was extremely predominant, and the other, high correlation as in ROKN. This tendency was more marked in the fast phase amplitude. Although it is generally accepted that OKN fast phase in SOKN is controlled by voluntary saccade, our results indicate that ROKN is more strongly controlled by reflective resetting eye movements, which is similar to the nystagmus fast phase in vestibular nystagmus.

Caloric irregularity in experimentally induced perilymphatic fistula.

The term "caloric irregularity" was coined to refer to a gross irregularity in the amplitude and/or frequency of a caloric-induced nystagmus, having a variable slow-phase velocity and prolonged duration. Twelve of 46 guinea pigs with experimentally induced perilymphatic fistula had irregular responses to the ice-water caloric test 1 week after creation of a fistula. The long-term vestibular consequences in animals with caloric irregularities were either resolution and return to normal function (i.e. caloric return) or continuing deterioration to canal paresis. Morphological examination of ears with caloric irregularity revealed that there had been partial collapse of the membranous labyrinth and the creation of a floating labyrinth.

Analysis of the Fast Phase of Per-Rotatory Nystagmus

We studied the relationship between the fast phase velocity and amplitude of per-rotatory nystagmus resulting from constant angular acceleration and deceleration stimulation. The relationship was nonlinear and was best fit to the exponential equation. We established the uppermost point of the data distribution along the resolution curve. In normal subjects the angular rotatory stimulation using a computer-controlled rotatory chair (ROKOS-6) with 5 degrees/s2 rotation was the best among three kinds of angular rotatory stimulation (1.2 and 5 degrees/s2). Compared to peripheral vestibular disorder the uppermost point of nystagmus had a tendency to be larger in amplitude in some cases with central vestibular disorder. In many cases with sudden deafness the same tendency was seen.

Changes in waveform of congenital nystagmus associated with biofeedback treatment.

A study was made of parameters of congenital nystagmus which responded to auditory biofeedback treatment. The parameters studied included foveation time, amplitude, and frequency. The patient's right retina was observed with an infrared television fundus camera, and the fundus image was recorded on video tape. The position of the eye during nystagmus, observed via the fundus camera and recorded on video, was analysed at every 1/60 second intervals. The displacement in degrees between the fixation target, projected on to the retina, and the foveola was measured for each interval. Using biofeedback, the subjects could voluntarily suppress nystagmus and prolong foveation time. A damping of the nystagmus amplitude, intensity, and frequency was observed. On the average the intensity decreased by about 40%, and the foveation time was prolonged by about 190%. After completion of the training all the patients reported a subjective improvement in their vision when suppressing their nystagmus. Possibly biofeedback training acts to reduce the nystagmus and extend foveation time, thereby improving the ability to fixate.

Effects of Intranasal Application of the Local Anaesthetic Xylocaine on Vestibulo-, Opto-Collic and Postural Reflexes of the Head, and on Tonic Immobility in Homing Pigeons: Implications for Experiments on Pigeon Homing

ABSTRACT Spraying lidocaine (Xylocaine), a local anaesthetic, into the nasal cavity of homing pigeons is a technique widely used to study the role of olfaction in pigeon homing. Studies in the laboratory revealed that Xylocaine suppressed vestibular and optokinetic nystagmus, roughly for as long as it suppressed olfaction, interfered with control of the head posture when the body was tilted in the sagittal plane, and prolonged tonic immobility. Amplitude and duration of both optokinetic and vestibular nystagmus were affected to the same extent. The effects are most probably caused by the drug’s rapid absorption via the mucous membranes in the nasal cavity and its transport in the blood to brain structures involved in integrating vestibular and visual inputs. The results provide room for nonolfactory explanations of the manifold effects on pigeon homing following administration of local anaesthetics to the nasal chambers.

Optokinetic nystagmus in homonymous hemianopia due to a strictly occipital lesion.

Optokinetic nystagmus (OKN) was tested in 15 patients with unilateral strictly occipital brain lesions and complete homonymous hemianopia and compared with findings in a group of normal controls. Quantitative analysis of the results in the patients revealed a bilateral disorder of OKN. When the stimulus was moved in the direction opposite to the hemianopic field, there was a significant decrease in optokinetic gain, and the amplitude of nystagmus decreased. There was no correlation between OKN and size of the residual macular field.

温度性眼振検査のコンピュータ計測

We have introduced a computer system to control and analyze equilibrium examinations in the clinical routine. An algorithm to analyze caloric responses, the usefulness of this system and parameters to evaluate the responses by computer analysis are reported. Caloric stimulation is given by 24°C cold and 50°C hot air at a 61/min. flow rate for one minute. Nystagmus waves elicited by the calorization are automatically identified, and the amplitude and velocity of nystagmus are calculated by on-line real time process. After all equilibrium examinations of a patient are completed, the caloric responses are computed and the results are printed on an X-Y plotter along with the results of optokinetic nystagmus and rotatory test. The slow phase velocity of each nystagmus are plotted and the values of duration, the number of nystagmus, maximum slow phase velocity and total amplitude in each calorization are indicated on the graph. The percentage of canal paresis (CP) and directional preponderance (DP) of each parameter are also printed on the graph. We can qualitatively observe caloric responses by the graph of the slow phase velocity and quantitatively evaluate disorders of the responses by the indicated values. Computer analysis of caloric nystagmus is very useful to evaluate responses correctly, particularly in cases showing such complicated responses as both CP and DP are combined or those are influenced by spontaneous nystagmus. We concluded that the maximum slow phase velocity is the best parameter to evaluate caloric test in the computer analysis.

Effects of flunarizine on induced nystagmus and cochlear blood flow.

The effects of flunarizine on induced nystagmus and cochlear blood flow were compared with those of cinnarizine and diphenidol. Flunarizine significantly inhibited caloric (cool water)-induced nystagmus frequency and duration of nystagmus in rabbits at 5 mg/kg i.v., whereas cinnarizine and diphenidol only slightly decreased the frequency of nystagmus at 5 mg/kg, i.v. As for optokinetic stimuli-induced nystagmus in rabbits, flunarizine significantly decreased the amplitude of nystagmus at 2.5 mg/kg i.v., and cinnarizine and diphenidol inhibited nystagmus at 5 mg/kg, i.v. Flunarizine had no effect on nystagmus induced by electrical stimulation of the lateral geniculate body in rabbits at doses up to 5 mg/kg, i.v. Flunarizine increased the cochlear blood flow in anesthetized guinea pigs dose-dependently (0.312-1.25 mg/kg i.v.) On the other hand, cinnarizine (0.625-2.5 mg/kg i.v.) and diphenidol (0.625-2.5 mg/kg i.v.) increased cochlear blood flow, but the duration of action of both cinnarizine and diphenidol was shorter than that of flunarizine at the same dose. As stated above, flunarizine inhibited nystagmus experimentally induced by caloric or optokinetic stimuli. Increased cochlear blood flow suggested that the enhancement of vestibular blood flow might play an important role in the treatment of vestibular dysfunctions with this drug.

眼振の波形分析について

New parameters of nystagmus (smoothness and kurtosis) were adopted for detailed analysis of nystagmus. Smoothness is related to the degree of fluctuation of the fixation point, and kurtosis reflects the sharpness of the turning point in nystagmus. These parameters were used to study optokinetic nystagmus under vestibular stimulation.The frequency and amplitude of nystagmus were increased from middle to high speed range, and a marked increase of the optokinetic adaptation limit was recorded. Increased smoothness in the slow phase and kurtosis at the terminal point of the quick phase were also observed. The labyrinth supports optokinetic nystagmus by making a subject catch optokinetic stimulise parately. This supporting effect is observed even at the low speed range of optokinetic nystagmus.

Effects of rectilinear acceleration, caloric and optokinetic stimulation of human subjects in the Spacelab D-1 mission

A set of vestibular experiments was performed during the course of the German Spacelab D-1 mission from 30 October to 6 November 1985 by a consortium of experimenters from various european countries. Similar to the Spacelab SL-1 mission all of the scientific crew members were theoretically and practically trained for the experiments. Baseline measurements for all tests were collected 113, 86, 44, 30 and 18 days prior to the mission and compared with data taken inflight, on the landing day and the consecutive 7 to 14 days. The hardware comprised mainly a motordriven accelerating platform, the SPACE SLED, and the vestibular helmet, a multi-purpose instrument in support of a variety of vestibular experiments including air-calorisation of the ears, optokinetic stimulation pattern presentation and optical and nystagmographic recording of eye movements. Measurements of the threshold for the perception of detection of whole body movement did not reveal any dramatic changes in the 2 measured axes inflight when compared to preflight values. Early postflight values show a significantly elevated threshold for all axes in 3 out of 4 subjects. The caloric nystagmus, already found during the SL-1 mission, was confirmed on all three tested subjects during the D-1 mission. It's amplitude and in some instances it's direction were influenced by horizontal acceleration on the SLED. The amplitude of optokinetic nystagmus increased when subjects were allowed to free-float over that seen when subjects were fixed. Stimulation of the neck receptors by roll movements of the body against the fixated head resulted in illusory object motion to the contralateral side. Torsional movements of the eyes during such neck receptor stimulation was present inflight and postflight, while it had not been observed preflight. Most results point to a reduction of otolithic effects in favour of visual and proprioceptive influences for spatial orientation.

Upbeat and downbeat nystagmus in a single case

A 26-year-old woman with neuro-Beh?et disease presented with a primary position upbeat nystagmus which decreased with tilting head. The nystagmus changed upbeat to downbeat with caloric stimulation. When she returned 22 months later, she had less upbeat nystagmus in primary position and had developed a downbeat nystagmus on gaze down. Again, head tilting had an effect on the nystagmus. At this time, the head tilt caused the amplitude of the downbeat nystagmus to increase. Both findings suggest a vestibular component in the patient's difficulty of eye movement, and an otolith-related component in the genesis of upbeat nystagmus.

Assessment of vestibulo-ocular reflexes in congenital nystagmus.

The vestibulo-ocular reflex and its suppression by fixation of a target rotating with the subject were tested in 18 subjects with congenital nystagmus using steps of constant velocity rotation and sinusoidal stimuli swept in frequency between 0.01 and 1.0 Hz. Responses to stopping stimuli were abnormal in waveform and of short duration in most subjects tested. This pattern was attributed to masking of the response by spontaneous eye movements and to adaptation. In contrast, during both oscillation in the dark and attempted suppression of the vestibulo-ocular reflex, all subjects had nystagmus that was modulated with the stimulus during all frequencies of stimulation. The phase relationship of the nystagmus to the motion stimulus was the same as in normal subjects. Estimates of the gain of the vestibulo-ocular reflex response were not meaningful because of contamination of the vestibular response by the congenital nystagmus waveforms. Modulation of amplitude and reversal of nystagmus in phase with the vestibular stimulus at all frequencies of oscillation were shown most clearly during attempted suppression of the vestibulo-ocular reflex. This finding is clinically useful because it establishes suppression as a test of the presence of vestibular function in congenital nystagmus.