The influence of VDT work on accommodation]

In order to evaluate the influence of visual display terminal (VDT) work on accommodation, accommodation responses, such as accommodation latency, accommodation velocity, amount of accommodation and refractive power, were measured with an infra-red optometer (TER-7 NIDEK). Comparisons were also made between parameter before VDT work and after VDT work. At first, comparison of the accommodation responses of playing with a video game, being engaged in VDT work and paper work, was made in 5 subjects. There was no significant difference after playing with the video game, slight accommodative dysfunction occurred after being engaged in paper work, but the accommodative dysfunction was most remarkable after being engaged in VDT work. In the next study, the accommodation responses of 22 subjects engaged in VDT work were measured. It was found that there was no significant change in accommodation latency, but a decrease of contraction velocity and relaxation velocity for accommodation was observed, and also a decrease in the amount of contraction response and relaxation response for accommodation was observed. Myopic change during relaxation also occurred. These results suggested that VDT work induced accommodation dysfunction.     

Temporal eye movement strategies during naturalistic viewing

The deployment of eye movements to complex spatiotemporal stimuli likely involves a variety of cognitive factors. However, eye movements to movies are surprisingly reliable both within and across observers. We exploited and manipulated that reliability to characterize observers' temporal viewing strategies while they viewed naturalistic movies. Introducing cuts and scrambling the temporal order of the resulting clips systematically changed eye movement reliability. We developed a computational model that exhibited this behavior and provided an excellent fit to the measured eye movement reliability. The model assumed that observers searched for, found, and tracked a point of interest and that this process reset when there was a cut. The model did not require that eye movements depend on temporal context in any other way, and it managed to describe eye movements consistently across different observers and two movie sequences. Thus, we found no evidence for the integration of information over long time scales (greater than a second). The results are consistent with the idea that observers employ a simple tracking strategy even while viewing complex, engaging naturalistic stimuli.     

Perceiving depth order during pursuit eye movement

Pursuit eye movements alter retinal motion cues to depth. For instance, the sinusoidal retinal velocity profile produced by a translating, corrugated surface resembles a sinusoidal shear during pursuit. One way to recover the correct spatial phase of the corrugation's profile (i.e. which part is near and which part is far) is to combine estimates of shear with extra-retinal estimates of translation. In support of this hypothesis, we found the corrugation's spatial phase appeared ambiguous when retinal shear was viewed without translation, but unambiguous when translated and viewed with or without a pursuit eye movement. The eyes lagged the sinusoidal translation by a small but persistent amount, raising the possibility that retinal slip could serve as the disambiguating cue in the eye-moving condition. A yoked control was therefore performed in which measured horizontal slip was fed back into a fixated shearing stimulus on a trial-by-trial basis. The results showed that the corrugation's phase was only seen unambiguously during the real eye movement. This supports the idea that extra-retinal estimates of eye velocity can help disambiguate ordinal depth structure within moving retinal images.     

Perception of suprathreshold stimuli during saccadic eye movement

We have investigated the extent to which a graded series of suprathreshold stimuli are perceptually weakened by saccadic suppression. Stimuli were brief decrements of variable amplitude in the illumination of a Ganzfeld. For each of several decrements presented during fixation, we determined a matching amplitude of decrement presented during saccades. The measure of saccadic suppression was the ratio of these two amplitudes. The matches made by three observers exhibit ratios as high as 6:1 (0.8 log unit of suppression) near the threshold. Suppression decreases systematically as the strength of the stimulus increases, reaching 0.1 log unit or less for stimuli 2 log units above threshold.     

Directionalization of visual targets during involuntary eye movement

Perceived visual direction with respect to one's self (egocentric direction) depends upon the retinal location of a target's image (its oculocentric direction) and concurrent information about the position of the eyes in the head. Information about eye position is presumably obtained from efference copy signals. However, in order to explain illusory target motion that can occur during reflexive eye movements (e.g., post-rotary nystagmus), these signals have been suggested to accompany only voluntary oculomotor responses. In the experiment reported here, manual pointing was used to assess the perceived direction of targets flashed during optokinetic afternystagmus, an involuntary movement of the eyes that occurs in darkness following optokinetic stimulation. Egocentric directionalization was essentially veridical, indicating that accurate eye position information is available during optokinetic afternystagmus. A model is proposed that accounts for illusory target motion during involuntary oculomotor responses by the cancellation of efference copy information about these eye movements with signals of oppositely directed head motion.     

Three-dimensional eye movement analysis of superior oblique myokymia

PURPOSE: To confirm the idea that sole contraction of the superior oblique muscle causes attacks of superior oblique myokymia (SOM). DESIGN: Observational case report. METHODS: A 43-year-old man presented with episodic monocular oscillatory eye movements. Three-dimensional eye movements were recorded using the magnetic search coil system and analyzed as rotation vector. The attacks of SOM consisted of intorsional, depressive, and abductive fast phases and their exponential decaying slow phases. RESULTS: Average direction of rotation axis for the fast phases while fixating straight ahead was 51.5 +/- 5.4 degrees from depression axis in vertical-torsional plane, 78.7 +/- 4.4 degrees from abduction axis in horizontal-torsional plane, and 76.3 +/- 4.3 degrees from abduction axis in horizontal-vertical plane (+/-SD, n = 50). Time constants of slow phases were less than 0.1 second. CONCLUSIONS: Quantitative three-dimensional analysis of SOM directly confirmed that the fast phases of SOM attacks were induced by the sole contraction of the superior oblique muscle.     

Correction of EOG with eye movement measured by the eye mark recorder system]

The electrooculogram (EOG) is usually necessary for the subject to fixate two targets alternately at a fixed visual angle. However, in the patients with poor vision, it can be difficult to fixate exactly. In such case, the results can be improved by using both the measurement of real eye position and the measurement of EOGs in combination. In this study, we measured subject's eye position simultaneously with the potential changes around his eyes as the subject pursued alternately two on-and-off visual targets which were horizontally placed on the cylindrical screen at a regular visual angle in front of his eyes. The EOG is obtained from those potential changes. If the difference between the target position and the fixating point can be calculated from the net eye movement measured with an eye camera, the error potential can be derived from this difference. Therefore, exact potential changes are obtained by correcting the measured potentials with the above error potentials. The authors were able to confirm that the potential changes were approximately proportional to the amplitude of saccadic eye movements within about 30 degrees in front of the eyes. Therefore, the simultaneous measurement of the potential changes and the eye position enable measurement of EOG without pursuing the targets by transforming the measured potentials into the exact values corresponding to the constant amplitudes of saccades.     

应该重视视频终端综合征的研究

本文介绍了视频终端（VDT）的特性及VDT综合征患者的眼部表现,VDT对眼部的影响研究涉及对视觉功能、视觉发育和眼表性状等各方面。此类研究目前尚处初步阶段,重视和深入研究才能为临床提供积极有效的防治方法。     

Retinal location and visual localization during pursuit eye movement

Experiments were performed to measure the mislocation of a brief visual stimulus presented during pursuit eye movements in different places over the retina. The results obtained show that the mislocation for regions 5° from fovea in the direction of motion is greater than in fovea. This fact shows that some kind of reorganization takes place in the visual localization mechanisms during pursuit eye movements. The results cast doubts on the concept of “perception time” which is often used to explain the visual mislocation phenomenon.     

Quantitative analysis of the slow phase in congenital nystagmus during convergence]

A previous report described that congenital nystagmus (CN) shows a lower intensity (frequency x amplitude) of spontaneous oscillation during convergence than for distance viewing. However, there has been no detailed report of quantitative analysis of the slow phase of CN during convergence. Therefore, in the present study, the slow phase of CN during convergence was analyzed in 7 patients horizontal and jerky type CN. The time constant of the slow phases were estimated using the repetitive non-linear least square method by a personal computer (NEC, PC 9801). The slow phases of CN for distance viewing were increasing-velocity exponentials, while those of CN during convergence were constant-velocity exponentials. The frequency, amplitude and mean velocity of the slow phase decreased during convergence. Thus, it was suggested that the velocity of the retinal image in CN decreased during convergence.     

Influence of stimulus parameters on visual sensitivity during saccadic eye movement

Visual threshold for stroboscope test flashes was measured during saccadic eye movements over various backgrounds and compared with measures obtained during eye fixation when the same backgrounds were “saccadically” displaced. Amount and time course of threshold change in the two situations compared well, suggesting no necessity for corollary discharge or other oculomotor interference with primary visual processes during eye movement. No significant threshold rise took place during saccades in the dark. Diffuse test flashes and small well focused flashes were affected differently by specific background conditions. Diffuse flashes were perceived with more difficulty during a saccade over a contour-free background than well focused, punctate stimuli. On the other hand, contours in the background raised saccadic thresholds for small stimuli much more than for diffuse test flashes. All threshold changes occurring during saccades were accentuated by increasing the background luminance.     

Direction and extent of perceived motion smear during pursuit eye movement

Smooth pursuit eye movements superimpose additional motion on the retinal image of untracked visual targets, potentially leading to the perception of motion smear and a distortion of the perceived direction of motion. Previously, we demonstrated an attenuation of perceived motion smear when the untracked target moves in the opposite direction of an ongoing pursuit eye movement. In this study, the extent of perceived motion smear and the direction of perceived smear were compared for a single bright dot that moved in a wide range of directions with respective to horizontal pursuit at 8 deg/s. Comparable data were obtained during fixation as a control. The results indicate that a significant attenuation of perceived motion smear occurs when the dot's motion includes a horizontal component in the opposite direction of eye movement. In contrast, the direction of perceived smear approximates the trajectory of the retinal image motion, during both fixation and pursuit. These results suggest a selective application of extra-retinal signals to compensate specific aspects of visual perception that results from the retinal image motion during smooth pursuit eye movements.     

Supranuclear disorders of eye movement

Eye movements are the result of activity in discrete systems. Saccades and smooth pursuit movements respond to target position and target velocity respectively. Compensatory responses to movements that alter the position of the eyes in space depend upon the vestibular and optokinetic systems. Vergence movements allow fusion and binocular vision. Eye movement abnormalities of supranuclear origin may be divided into nystagmus, other ocular oscillations, saccadic dysfunction, smooth pursuit dysfunction, gaze palsy, tonic deviation, and vergence disability. An algorithm for the analysis of supranuclear eye movement disorders is presented.     

Kinematics of eye movement.

In a simplified fashion, the motion of the eyeball in its orbit consists of rotations around a fixed point. Therefore, this motion can be described in terms of Euler's angles of rigid body dynamics. However, there is a physiological constraint in the motion of the eye which reduces to two its degrees of freedom, so that one of Euler's angles is not an independent variable. This paper reviews the basic features of the kinematics of the eye and the laws governing its motion.     

Supranuclear disorders of eye movement

Eye movements are the result of activity in discrete systems. Saccades and smooth pursuit movements respond to target position and target velocity respectively. Compensatory responses to movements that alter the position of the eyes in space depend upon the vestibular and optokinetic systems. Vergence movements allow fusion and binocular vision.
Eye movement abnormalities of supranuclear origin may be divided into nystagmus, other ocular oscillations, saccadic dysfunction, smooth pursuit dysfunction, gaze palsy, tonic deviation, and vergence disability.
An algorithm for the analysis of supranuclear eye movement disorders is presented.     

先天性眼球震颤眼球运动波形的相图特点分析

背景 先天性眼球震颤患者的眼球运动波形表现各异,其时间动力学的非线性特征复杂,常规的时间序列波形图不便于对患者进行临床诊断及评估.眼球运动系统是非线性反馈控制系统,而相图法是一 种用于描绘非线性系统运动特征的分析技术,但相图法在先天性眼球震颤检测中的应用尚未见报道. 目的尝试建立先天性眼球震颤眼球运动波形的相图法分析技术,为先天性眼球震颤的临床诊断与定量评估提供新的方法.方法 采用前瞻性病例观察设计,纳入2012年4月至2013年2月在天津市眼科医院就诊的25例先天性眼球震颤患者,其中先天性运动性眼球震颤(CMN)患者12例,隐性眼球震颤(LN)患者13例.所有患者行视频眼动图(VOG)检查,对VOG数据进行格式转换后,采用Matlab程序对数据进行处理,得到每个眼动波形周期的相位图,并从相位图上测得周期位移(CPS)、慢相峰值速度(SPV)及其标准化值(SSPV)、快相峰值速度(FPV)及其标准化值(SFPV).比较先天性眼球震颤波形速度递增型和速度递减型的测量参数.结果 先天性眼球震颤的眼球运动相图呈现周期性规律性往复运动轨迹,其慢相过程表现为密集带状轨迹,快相过程表现为稀疏环状轨迹.CMN的眼球运动波形以速度递增型为主,而LN的眼球运动波形以速度递减型为主,2种波形相图轨迹走行均呈顺时针方向.速度递增型CPS、SPV及FPV分别为(4.646±1.565)、(223.821±114.049)和(767.481±263.560)°/s,速度递减型CPS、SPV及FPV分别为(9.373±4.189)、(357.531±154.300)和(1 148.706±541.362)°/s;速度递增型中SPV和FPV与CPS间均呈显著正相关(rSPV-CPS=0.685,P=0.000;rFPV-CPS=0.680,P=0.000);速度递减型中SPV和FPV与CPS间均呈显著正相关(rSPV-CPS=0.783,P=0.000;rFPV-CPS=0.803,P=0.000).2种波形FPV均大于SPV,差异均有统计学意义(速度递增型:t=6.558,P=0.000;速度递减型:t=5.068,P=0.000).速度递增型SSPV为(48.062±15.365)°/s,略大于速度递减型的(41.099±17.027)°/s,但差异无统计学意义(t=1.070,P=0.296);速度递增型SFPV为(171.186±47.825)°/s,大于速度递减型的(125.317±38.266)°/s,差异有统计学意义(t=2.658,P=0.014).结论 相图法能够直观显示先天性眼球震颤眼球运动轨迹的周期性动态特征,便于测量其不同时相的运动幅度、速度等参数.     

Probabilistic modeling of eye movement data during conjunction search via feature-based attention

Where the eyes fixate during search is not random; rather, gaze reflects the combination of information about the target and the visual input. It is not clear, however, what information about a target is used to bias the underlying neuronal responses. We here engage subjects in a variety of simple conjunction search tasks while tracking their eye movements. We derive a generative model that reproduces these eye movements and calculate the conditional probabilities that observers fixate, given the target, on or near an item in the display sharing a specific feature with the target. We use these probabilities to infer which features were biased by top-down attention: Color seems to be the dominant stimulus dimension for guiding search, followed by object size, and lastly orientation. We use the number of fixations it took to find the target as a measure of task difficulty. We find that only a model that biases multiple feature dimensions in a hierarchical manner can account for the data. Contrary to common assumptions, memory plays almost no role in search performance. Our model can be fit to average data of multiple subjects or to individual subjects. Small variations of a few key parameters account well for the intersubject differences. The model is compatible with neurophysiological findings of V4 and frontal eye fields (FEF) neurons and predicts the gain modulation of these cells.