Abstract
Purpose :
Amblyopia results from abnormal visual experience during development and is a leading cause of visual impairment in children and young adults. Pathologic interocular suppression of the amblyopic eye by the fellow eye serves as a quantifiable property and pathogenic driver of amblyopia. Recently development and implemented “dichoptic”/antisuppression amblyopia therapies have produced mixed results. We aimed to deepen the understanding of pathologic interocular suppression in the context of amblyopia at the level of the visual cortex using a mouse model.
Methods :
Juvenile mice underwent chronic electrode implantation prior to visual stimulus presentation at P35. A 3D monitor and polarized lenses were used to selectively present phase-reversing sinusoidal grating stimuli to each eye. Awake visual evoked potentials (VEPs) elicited by a 45-degree grating presented to the contralateral eye were monitored as the concordant or discordant (135-degree) orientation was gradually presented to the ipsilateral eye.
Results :
In naïve animals, binocular discordant stimuli significantly reduced VEP magnitudes compared with concordant stimuli primarily through disruption of the late, positive component of the VEP waveform. Reversing the contrast ramp direction showed the same monocular-binocular differences, suggesting these observations were not an artifact of presentation order. VEP responses recorded through the opposite hemisphere showed similar effects of rivalrous binocular stimulation on the VEP waveform. Introducing the discordant orientation in the same, contralateral eye produced a similar suppressive effect but carried a higher contrast threshold, suggesting interocular modulation of cross-orientation suppression. Incrementally adjusting the ipsilateral eye stimulus from concordant to discordant reveals a 15-degree threshold for interocular cross-orientation suppression. Seven days of monocular deprivation disrupted suppression of the early, negative VEP component by binocular discordant stimulus presentation but did not alter effects on the late component.
Conclusions :
We have established a useful model of binocular rivalry to study interocular suppression. Disruption of interocular suppression that accompanies monocular deprivation serves to validate this model as tool to study the interplay between interocular suppression and amblyopia development and recovery.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.