Nystagmus Gain Research Articles

The Effect of Weighted Contact Lens on Physiological Nystagmus in Young Healthy Subjects

Background and Aim: Contact lenses correct the visual functioning of patients with low vision due to congenital nystagmus. This research presents a new method to reduce nystagmus using contact lenses in healthy subjects. Methods: Thirty-three normal people (13 women, 20 men) aged 18 to 25 with an average age of 23.3 years participated in this study. In the studied subjects, nystagmus was evoked by an optokinetic stimulus. Then, it was measured and recorded. Next, the Conventional Contact Lens (CCL) and a special lens that was designed and made heavier than the conventional lenses were placed in the eyes of the participants. Once again, nystagmus was recorded with the optokinetic stimulus while the contact lens was placed in the participant’s eyes. Results: No significant difference was observed for the Slow Phase Velocity (SPV) and gain of nystagmus with and without CCL (p>0.05), but this parameter had a significant difference with and without Weighted Contact Lenses (WCL) (p<0.05). Also, the comparison between the two lenses demonstrated a significant difference (p<0.05), which indicates the positive effect of the WCL in reducing the SPV and gain of nystagmus. Conclusion: Using weighted contact lenses can significantly reduce the SPV and gain of optokinetic nystagmus in healthy subjects. Investigating the effect of this lens in inhibiting pathological nystagmus is recommended in future research. Keywords: Nystagmus; optokinetic nystagmus; weighted contact lens

Visual Eye movement-vestibular ocular balance assessment in the diagnosis of central and peripheral vertigo

Objective To explore the role of visual oculomotor-vestibular eye balance function in the diagnosis of central and peripheral vertigo. Methods From January 2015 to June 2016, one hundred and sixty-two patients with central vertigo who were treated at Kailuan General Hospital were enrolled in the study, including 124 males and 38 females, aged (64.09±10.98) years old; there were 166 cases of peripheral vertigo, 75 males and 91 females, aged (52.13±12.20) years old.Spontaneous nystagmus test, gaze test, position test, saccade test, smooth visual tracking test, visual single-speed test, visual sinus test, swivel chair rotation-emergency stop test using infrared video nystagmus and static balance posture instrument, open-closed eye hard plate erect test, open-closed eye sponge soft bottom erect test balance function electrophysiological test were conducted. Results The detection rate of pathological spontaneous nystagmus and pathological gaze nystagmus was higher in the central vertigo group than that in the peripheral vertigo group (χ2=5.674, 16.458, P<0.05). The occurrence rate of positional nystagmus was higher in peripheral vertigo group than that in central vertigo group (χ2=48.896, P<0.001). The abnormal rate of scanning test, stable visual tracking test, visual movement single speed and sinusoidal test, and static balance posture test were higher in the central vertigo group than those in the peripheral vertigo group (χ2=137.169, 166.972, 150.877, 150.877, 27.273, P<0.001), while the abnormal rate of rotating chair sudden stop test was higher in the central vertigo group than that in the peripheral vertigo group (χ2=51.000, P<0.001). The abnormal results were mainly scanned underflush and slow scan in central vertigo group (χ2=103.846, 4.296, P<0.05), stable visual tracking curve (χ2=147.389, 4.296, P<0.05) in type III-IV, and the gain of nystagmus decreased unilaterally and bilaterally (χ2=47.531, 44.477, 52.529, 53.255, P<0.001). Anomalies of proprioception in reverse and vertical nystagmus and static balance posture were induced by rotating chair sudden stop test (χ2=11.847, 23.778, P<0.001), while peripheral vertigo group showed unilateral decrease of nystagmus gain induced by rotating chair sudden stop test.(χ2=79.771, P<0.001). Conclusion The patients with peripheral vertigo have obvious body position spontaneous vestibular response and vestibular oculomotor system dysfunction, while the patients with central vertigo mainly have visual and oculomotor system dysfunction, and may be accompanied by vestibular oculomotor system and vestibular spinal reflex dysfunction. Key words: Vertigo; Videonystagmography; Static equilibrium posture

Modulation of vestibulo-ocular reflex (VOR) by active stabilization of head to trunk.

Horizontal vestibulo-ocular reflex (VOR) with covered eyes was tested in 15 healthy subjects sitting on a rotation chair (40 degrees, 0.05, 0.1, 0.2, 0.33 Hz) under two conditions: (a) head fixed to chair by a neck support; (b) with instruction to turn the head together with the passively moved trunk. In situation (b), saccadic amplitudes/sec, nystagmus frequency, gain of nystagmus slow phase velocity and amplitudes of maximum eye shift were enhanced significantly. The phase of maximum eye shift changed from 180 degrees up to 270 degrees with respect to stimulus position. The distribution of nystagmus saccades over the stimulus period showed enhanced peak values and a slight phase shift.

Vestibulo-ocular reflex (VOR), cervico-ocular reflex (COR) and its interaction in active head movements.

In normal adults the vestibulo-ocular reflex (VOR) and the cervico-ocular reflex (COR) were investigated during passive and active head or body movements, respectively. Sinusoidal rotations around the vertical axis of the body at frequencies of 0.05, 0.1, and 0.2s-1 and total amplitudes of 20 degrees, 40 degrees, 60 degrees, or 80 degrees were employed. The average eye deviations (Schlagfeld) during VOR were directed opposite to the direction of the head turning. During COR, however, slow eye deviations of higher amplitude were anticompensatory relative to the fixed head. During active head turnings the average eye deviations showed the same anticompensatory direction as in COR, but were still larger. The increased with stimulus amplitudes up to 60 degrees. At least a weak cervical nystagmus was elicited in all subjects, with its fast phases beating in the direction of the relative head movement. Its gain reached marked values up to 0.5, but only for peak stimulus velocities below 25%. The nystagmus gain during active head turnings was only slightly higher than during VOR. With higher stimulus velocities, large anticompensatory saccades appeared just before the change of stimulus direction; these are typical for active head movements, but were also found during COR.