Example of fixational saccade and drifts in a 1.5-second epoch of eye positions recorded from an adult and a child.

<p>Horizontal and vertical eye positions were recorded from the right and left eye (LV: left vertical; RV: right vertical; LH: left horizontal; RH: right horizontal). Eye positions are plotted on y-axis while x-axis depicts the corresponding time. Colored traces depict right eye position while gray traces illustrate the left eye. Arrows depict fixational saccades. (A) An example of fixational eye movements in an adult subject (subject 20 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0175295#pone.0175295.t001" target="_blank">Table 1</a>). The fixational saccade has different amplitudes in the vertical direction (red arrow) between the two eyes suggesting a disconjugacy. (B) An example of fixational eye movement in a child (subject 7 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0175295#pone.0175295.t001" target="_blank">Table 1</a>). Arrows depict fixational saccade. The amplitude of the fixational saccade is equal suggesting their conjugate nature in the child.</p

Fixational saccades are more disconjugate in adults than in children - Fig 2

<p>(A) Distribution of microsaccade amplitude, when saccades were identified using clustering algorithm proposed by Otero-Millan et al. (2014). A normalized number of microsaccades are plotted on the y-axis, while x-axis depicts the amplitude of microsaccades in degrees. Red lines depict the distribution of microsaccades in adults, while blue lines depict children. The two distributions were significantly different (Two-sample Kolmogorov-Smirnov test p<0.0001). (B) Kinematic properties of microsaccades quantified in the main-sequence analysis. Eye velocities are plotted on the y-axis while the corresponding positions are plotted on the x-axis. Each data point depicts one saccade. Blue symbols illustrate children, while red data points are adults. (C) Comparison of the amplitude disconjugacy and (D) directional disconjugacy of fixational saccades. In both panels, the right eye is plotted on y-axis while the left eye is plotted on the x-axis. Red symbols depict adults, while children are shown in blue data points. Grey line is an equality line. The red points, suggesting adults, have larger scatter showing more amplitude and directional disconjugacy compared to pediatric patients. </p

Demographics and log BCEA of fixation data of all the study participants.

<p>Demographics and log BCEA of fixation data of all the study participants.</p

Bivariate contour ellipse analysis.

<p>Bivariate contour ellipse analysis.</p

Demographic and clinical features.

<p>Demographic and clinical features.</p

Correlation of fixational saccade amplitude with peak drift velocity and eye position variance.

<p>Correlation of fixational saccade amplitude with peak drift velocity and eye position variance.</p

Frequency of microsaccades and fixational saccades.

<p>Frequency of microsaccades and fixational saccades.</p

Comparison of fixational saccade amplitude in viewing and non-viewing eye.

<p>Comparison of fixational saccade amplitude in viewing and non-viewing eye.</p

Characteristics of ocular drifts.

<p>Characteristics of ocular drifts.</p

Abnormal Fixational Eye Movements in Amblyopia - Fig 2

<p>(A) Scatter plots of summary of the effects of severity of amblyopia on median amplitude of fixational saccades during fellow eye viewing condition (x-axis) and amblyopic eye viewing condition (y-axis). Each symbol depicts one subject whereas the symbol type represents severity of amblyopia. The dashed line is the equality line. (B, C) Summarizes the distribution of the fixational saccade amplitude during fellow eye viewing condition (B) and amblyopic eye viewing condition (C). A normalized number of events in a given bin is plotted along the y-axis while the x-axis represents the bins of fixational saccade amplitude of the viewing eye. The gray line illustrates the normalized frequency histogram of microsaccade amplitude in normal controls. The red, green and black lines represent mild, moderate and severe amblyopia subjects.</p