Version: 2019.3
public Camera.MonoOrStereoscopicEye stereoActiveEye ;

説明

Returns the eye that is currently rendering. If called when stereo is not enabled it will return Camera.MonoOrStereoscopicEye.Mono.
If called during a camera rendering callback such as OnRenderImage it will return the currently rendering eye.
If called outside of a rendering callback and stereo is enabled, it will return the default eye which is Camera.MonoOrStereoscopicEye.Left.