VisualEyes: A Modular Software System for Oculomotor Experimentation

Abstract

Eye movement studies have provided a strong foundation forming an understanding of how the brain acquires visual information in both the normal and dysfunctional brain. 1 However, development of a platform to stimulate and store eye movements can require substantial programming, time and costs. Many systems do not offer the flexibility to program numerous stimuli for a variety of experimental needs. However, the VisualEyes System has a flexible architecture, allowing the operator to choose any background and foreground stimulus, program one or two screens for tandem or opposing eye movements and stimulate the left and right eye independently. This system can significantly reduce the programming development time needed to conduct an oculomotor study. The VisualEyes System will be discussed in three parts: 1) the oculomotor recording device to acquire eye movement responses, 2) the VisualEyes software written in LabView, to generate an array of stimuli and store responses as text files and 3) offline data analysis. Eye movements can be recorded by several types of instrumentation such as: a limbus tracking system, a sclera search coil, or a video image system. Typical eye movement stimuli such as saccadic steps, vergent ramps and vergent steps with the corresponding responses will be shown. In this video report, we demonstrate the flexibility of a system to create numerous visual stimuli and record eye movements that can be utilized by basic scientists and clinicians to study healthy as well as clinical populations. ProtocolAn overview of the key elements needed to conduct an oculomotor experiment is shown in figure 1. Each block in the flow chart will be discussed in detail below. INSTRUMENTATION SET-UP:2. CALIBRATION: VISUALEYES SOFTWARE:Page 1 of 6 Journal of Visualized Experiments www.jove.comCopyright © 2011 Journal of Visualized Experiments 1. Any type of eye movement monitor can be used for this system. We will demonstrate an infrared limbus tracking and a video monitoring system. 2. For tandem tracking movements such as saccadic or smooth pursuit, a single computer can be used for the visual display. To study opposing eye movements such as vergence or the interaction of vergence with tandem version movements (ie, vergent with saccadic stimuli) a haploscope is needed with two computer monitors for visual display, see figure 2.1. Calibration is needed to convert one set of metrics into another. Eye movements are typically indicated in degrees (°) of rotation shown in figure 3. However, computer monitors use pixel values compared to vision researchers who often denote the visual stimuli in degrees. Hence, a conversion is needed to convert the pixel values to degrees. One can use trigonometry to calculate where to place the physical targets to calibrate the visual displays. For example, if the stimulus on the computer screen aligns with a 2°physical target (see figure 2) then that pixel value corresponds to a 2°stimulus. 2. To calibrate the system, the operator needs to open Pixel2Deg.vei within the Vi...

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