Quantification of Oculomotor Responses and Accommodation through Instrumentation and Analysis Toolboxes

Abstract

Through the purposeful stimulation and recording of eye movements, the fundamental characteristics of the underlying neural mechanisms of eye movements can be observed. VisualEyes2020 (VE2020) was developed based on the lack of customizable software-based visual stimulation available for researchers that does not rely on motors or actuators within a traditional haploscope. This new instrument and methodology have been developed for a novel haploscope configuration utilizing both eye tracking and autorefractor systems. Analysis software that enables the synchronized analysis of eye movement and accommodative responses provides vision researchers and clinicians with a reproducible environment and shareable tool. The Vision and Neural Engineering Laboratory's (VNEL) Eye Movement Analysis Program (VEMAP) was established to process recordings produced by VE2020's eye trackers, while the Accommodative Movement Analysis Program (AMAP) was created to process the recording outputs from the corresponding autorefractor system. The VNEL studies three primary stimuli: accommodation (blur-driven changes in the convexity of the intraocular lens), vergence (inward, convergent rotation and outward, divergent rotation of the eyes), and saccades (conjugate eye movements). The VEMAP and AMAP utilize similar data flow processes, manual operator interactions, and interventions where necessary; however, these analysis platforms advance the establishment of an objective software suite that minimizes operator reliance. The utility of a graphical interface and its corresponding algorithms allow for a broad range of visual experiments to be conducted with minimal required prior coding experience from its operator(s).

Figure 1:. Haploscope control and recording equipment configuration.

Example of the VE2020’s display indexing for clockwise monitor ordering and dimensioning. Here, 1 is the control monitor, 2 is the near-left display monitor, 3 is the far-left display monitor, 6 is the calibration board (CalBoard), 4 is the far-right display monitor, and 5 is the near-right display monitor.

Figure 2:. Breakout box switch references.

Demonstration of the proper NI 2090A switch positions.

Figure 3:. Stimulated degrees to monitor pixels.

Depiction of the operator view for calibrating the VE2020. From left to right, a table of values for the recorded pixels corresponding to a known degree value is provided for a given stimulus monitor selection (stretch mode ID) with a fixed aspect ratio, given file name, background stimulus (BG), and foreground stimulus (Line).

Figure 4:. Pixel to degree calibration slopes.

Monocular calibration curve for known degree values and measured pixel values.

Figure 5:. Calculated degrees of rotation.

Method of calculating the angular displacement for both saccadic eye movements and vergence movements with a known distance to the target (X) and inter-pupillary distance (IPD).

Figure 6:. Stimulus library.

Utilizing text-editing software, the format shown for identifying the port communications, baud rate, data size, and parity, as well as the library of stimulus files (.vei), provides the VE2020 with the necessary configurations and stimulus file names to run successfully.

Figure 7:. Monocular calibration and correlation slopes.

An example of the calibration of eye movement data from voltage values to degrees of rotation.

Figure 8:. Eye movement software classification.

Classification of the stimulated eye movement responses.

Figure 9:. Eye movement response software analysis.

An example of plotted convergence responses stimulated by a 4° symmetrical step change (right), with individual eye movement response metrics presented tabularly (left) and group-level statistics displayed tabularly below the response metrics.

Figure 10:. AMAP software frontend.

The figure displays the main user interface for the AMAP with highlighted sections for the graphical presentation (graphical options) of data and data analysis (metric modifications).

Figure 11:. Eye movement response ensembles.

The ensemble plots of vergence steps (left) and saccades (right) stimulated using the VE2020 are shown. Each eye movement position trace (degrees) is plotted as a uniquely colored line and overlayed with the group-level velocity response in red.

Figure 12:. Accommodative movement response ensembles.

The figure demonstrates the AMAP ensemble function, which creates overlays of each individual movement response trace (gray) and the average response (green).