Optomotry device

To assess recovery of primary vision, adult killifish of 6‐weeks‐, 12‐weeks‐, 18‐weeks‐, and 24‐weeks‐old were subjected to an optokinetic response test (Van houcke et al., 2017 (link)) at 0, 2, 4, 7, 10, 14, 18, 35, 42, 55, and 60 days following bilateral ONC. First, fish were anesthetized briefly in 0.03% Tris‐buffered tricaine. After positioning them in a custom‐made glass chamber, a continuous water flow was provided, allowing the fish to reawaken and breathe while being immobilized. The glass chamber was then placed in an OptoMotry device (Cerebral Mechanics) for assessment of visual acuity. The maximal spatial frequency provoking an optokinetic reflex of each fish was determined, while velocity and contrast were kept fixed at 15 deg/s and 100%, respectively. Each trial was initiated with a spatial frequency of 0.02 (c/d), which increased stepwise following a staircase model. One day on beforehand, fish were allowed for an adaptation period in the system. For every age group, the optokinetic reflex of at least six fish was followed up (with exception of 6‐weeks‐old fish at 10 dpi (n = 5) and of 24‐weeks‐old fish at 18 dpi (n = 4)).

Visual acuity and contrast sensitivity were evaluated using the OptoMotry device from Cerebral Mechanics (Medicine Hat, Alberta, AB, Canada). Briefly, the individual mouse was placed on the central platform inside the chamber, and computer monitors surrounding the mouse projected a virtual stimulus in the form of a sine wave. Animals tracked the grating with head and neck movements in the direction of grid rotation clockwise or counterclockwise. The system measured visual function in each eye separately because motion in the temporal to the nasal direction of either eye elicited a tracking response. A camera above monitored the behavior of the mouse, allowing the rater to detect the response in corporal and give a score of yes or no. To examine visual acuity, spatial frequency thresholds (cycles per degree) were measured by systematically increasing the spatial frequency of the grating (decreasing the bar width) at full contrast until mice could no longer track. The rotation speed was fixed at 12 degrees per second, and the data were managed and generated by the software. Data are presented as responses from both eyes.