The Integrated Optokinetic Nystagmus Inter-saccadic Interval Scales Statistical Different In a Group of Vertigo Patients Depended On The Stimulation Velocity, But Not For Healthy Subjects

Optokinetic nystagmus is rhythmic eye movements, back and forth, with a slow and fast phase, when the eyes are presented for full-field visual stimulus. OKN was recorded in 20 healthy subjects and 20 patients suffering from vertigo, for four conditions: stripes moving 30 o/s left and right and 60 o/s left and right. Calculating the scaling, the spread over time, for the integrated optokinetic nystagmus inter-saccadic interval, the time intervals between the onsets of consecutive fast components, shows lower Hurst exponent for velocity stimulation of 30o/s compared to 60o/s for both patients and health subjects, but only reach statistical differences for the group of patients.

A Dichoptic Optokinetic Nystagmus Paradigm for Interocular Suppression Quantification in Intermittent Exotropia

Purposes: To investigate the effectiveness of a dichoptic optokinetic nystagmus (dOKN) test to objectively quantify interocular suppression in intermittent exotropia (IXT) patients during the states of orthotropia and exodeviation.Methods: The OKN motion in subjects (15 controls and 59 IXT subjects) who viewed dichoptic oppositely moving gratings with different contrast ratios was monitored and recorded by an eye tracker. Interocular suppression in control subjects was induced using neutral density (ND) filters. The OKN direction ratios were fitted to examine the changes of interocular suppression in subjects under different viewing states. Two established interocular suppression tests (phase and motion) were conducted for a comparative study.Results: The dOKN test, which requires a minimal response from subjects, could accurately quantify the interocular suppression in both IXT and control subjects, which is in line with the established interocular suppression tests. Overall, although comparative, the strength of interocular suppression detected by the dOKN test (0.171 ± 0.088) was stronger than those of the phase (0.293 ± 0.081) and the motion tests (0.212 ± 0.068) in the control subjects with 1.5 ND filters. In IXT patients, when their eyes kept aligned, the dOKN test (0.58 ± 0.09) measured deeper visual suppression compared with the phase (0.73 ± 0.17) or the motion test (0.65 ± 0.14). Interestingly, strong interocular suppression (dOKN: 0.15 ± 0.12) was observed in IXT subjects during the periods of exodeviation, irrespective of their binocular visual function as measured by synoptophore.Conclusion: The dOKN test provides efficient and objective quantification of interocular suppression in IXT, and demonstrates how it fluctuates under different eye positions.

Impact of walking speed and motion adaptation on optokinetic nystagmus-like head movements in the blowfly Calliphora

The optokinetic nystagmus is a gaze-stabilizing mechanism reducing motion blur by rapid eye rotations against the direction of visual motion, followed by slower syndirectional eye movements minimizing retinal slip speed. Flies control their gaze through head turns controlled by neck motor neurons receiving input directly, or via descending neurons, from well-characterized directional-selective interneurons sensitive to visual wide-field motion. Locomotion increases the gain and speed sensitivity of these interneurons, while visual motion adaptation in walking animals has the opposite effects. To find out whether flies perform an optokinetic nystagmus, and how it may be affected by locomotion and visual motion adaptation, we recorded head movements of blowflies on a trackball stimulated by progressive and rotational visual motion. Flies flexibly responded to rotational stimuli with optokinetic nystagmus-like head movements, independent of their locomotor state. The temporal frequency tuning of these movements, though matching that of the upstream directional-selective interneurons, was only mildly modulated by walking speed or visual motion adaptation. Our results suggest flies flexibly control their gaze to compensate for rotational wide-field motion by a mechanism similar to an optokinetic nystagmus. Surprisingly, the mechanism is less state-dependent than the response properties of directional-selective interneurons providing input to the neck motor system.

Risk factors related balance disorder for patients with dizziness/vertigo

Background When dizziness/vertigo patients presented with balance disorder, it will bring severe morbidity. There is currently lack of research to explore risk factor related balance disorder in dizziness patients, especially in those who walk independently. Aim To investigate risk factors related balance disorder in dizziness/vertigo patients who walk independently. Methods Medical data of 1002 dizziness/vertigo patients registered in vertigo/balance disorder registration database were reviewed. The demographic data, medical history, and risk factors for atherosclerosis (AS) were collected. Enrolled dizziness/vertigo patients could walk independently, completed Romberg test, videonystagmography (VNG), and limits of stability (LOS). The subjective imbalance was patient complained of postural symptom when performing Romberg test. Multivariable logistic regression analyzed risk factors related balance disorder. The receiver operating characteristic (ROC) curve evaluated the utility of regression model. Results Five hundred fifty-three dizziness/vertigo patients who walk independently were included in the final analysis. According to LOS, patients were divided into 334 (60%) normal balance and 219 (40%) balance disorder. Compared with normal balance, patients with balance disorder were older (P = 0.045) and had more risk factors for AS (P<0.0001). The regression showed that risk factors for AS (OR 1.494, 95% CI 1.198–1.863), subjective imbalance (OR 4.835, 95% CI 3.047–7.673), and abnormality of optokinetic nystagmus (OR 8.308, 95% CI 1.576–43.789) were related to balance disorder. The sensitivity and specificity of model were 71 and 63% (P<0.0001). The area under the curve (AUC) was 0.721. Conclusions Risk factors for AS, subjective imbalance, and abnormality of optokinetic nystagmus were predictors for balance disorder in patients with dizziness/vertigo who walk independently.

Gain control by sparse, ultra-slow glycinergic synapses

Retinal ON starburst amacrine cells (SACs) play a critical role in computing stimulus direction, partly in service of image stabilization by optokinetic nystagmus. ON SAC responses are sculpted by rich GABAergic innervation, mostly from neighbouring SACs. Surprisingly, however, we find that glycinergic narrow field amacrine cells (NACs) serve as their dominant source of inhibition during sustained activity. Although NAC inputs constitute only ~5% of inhibitory synapses to ON SACs, their distinct input patterns enable them to drive glycine inhibition during the both light increments and decrements. NAC to ON SAC inhibition appears to be mediated by ultra-slow non-canonical glycine receptors containing the α4 subunit, which effectively summate during repetitive stimulation. Glycinergic inhibition strongly decreases the output gain of the SACs, ensuring that their direction-selective output is maintained over their operating range. These results reveal an unexpected role for glycinergic pathways and receptor kinetics in modulating direction selectivity in the retina.

Risk Factors Related Balance Disorder for Patients With Dizziness/Vertigo

Background: When dizziness/vertigo patients presented with balance disorder, it will bring severe morbidity. There is currently lack of research to explore risk factor related balance disorder in dizziness patients, especially in those who walk independently.Aim: To investigate risk factors related balance disorder in dizziness/vertigo patients who walk independently.Methods: Medical data of 1002 dizziness/vertigo patients registered in vertigo/balance disorder registration database were reviewed. The demographic data, medical history, and risk factors for atherosclerosis (AS) were collected. Enrolled dizziness/vertigo patients could walk independently, completed Romberg test, videonystagmography (VNG), and limits of stability (LOS). The subjective imbalance was patient complained of postural symptom when performing Romberg test (whether eyes open or close). Multivariable logistic regression analyzed risk factors related balance disorder. The receiver operating characteristic (ROC) curve evaluated the utility of regression model.Results: 553 dizziness/vertigo patients who walk independently were included in the final analysis. According to LOS, patients were divided into 334 (60%) normal balance and 219 (40%) balance disorder. Compared with normal balance, patients with balance disorder were older (P=0.045) and had more risk factors for AS (P＜0.0001). The regression showed that risk factors for AS (OR 1.494, 95% CI 1.198-1.863), subjective imbalance (OR 4.835, 95% CI 3.047-7.673), and abnormality of optokinetic nystagmus (OR 8.308, 95% CI 1.576-43.789) were related to balance disorder. The sensitivity and specificity of model were 71% and 63% (P＜0.0001). The area under the curve (AUC) was 0.721.Conclusions: Risk factors for AS, subjective imbalance, and abnormality of optokinetic nystagmus were predictors for balance disorder in patients with dizziness/vertigo who walk independently.

The effect of refractive error on optokinetic nystagmus

Subjective refraction is the gold-standard for prescribing refractive correction, but its accuracy is limited by patient’s subjective judgment about their clarity of vision. We asked if an involuntary eye movement, optokinetic nystagmus (OKN), could serve as an objective measure of visual-clarity, specifically measuring the dependence of OKN—elicited by drifting spatial-frequency filtered noise—on mean spherical equivalent (MSE) refractive error. In Experiment 1 we quantified OKN score—a measure of consistency with stimulus-direction—for participants with different MSEs. Estimates of MSE based on OKN scores correlate well with estimates of MSE made using autorefraction (r = 0.878, p < 0.001, Bland–Altman analysis: mean difference of 0.00D (95% limits of agreement: − 0.85 to + 0.85D). In Experiment 2, we quantified the relationship between OKN gain (ratio of tracking eye-movement velocity to stimulus velocity) and MSEs (− 2.00, − 1.00, − 0.50, 0.00 and + 1.00D) induced with contact lenses for each participant. The mean difference between measures of MSE based on autorefraction or on OKN gain was + 0.05D (− 0.90 to + 1.01D), and the correlation of these measures across participants was r = 0.976, p < 0.001. Results indicate that MSE attenuates OKN gain so that OKN can be used as an objective proxy for patient response to select the best corrective lens.