The XRView interface's read-only eye property is a string indicating which eye's viewpoint the XRView represents: left or right. For views which represent neither eye, such as monoscopic views, this property's value is none.

A string that can be one of the following values:

left

The XRView represents the point-of-view of the viewer's left eye.

right

The view represents the viewer's right eye.

none

The XRView describes a monoscopic view, or the view otherwise doesn't represent a particular eye's point-of-view.

The primary purpose of this property is to allow the correct area of any pre-rendered stereo content to be presented to the correct eye. For dynamically-rendered 3D content, you can usually ignore this and render each of the viewer's views, one after another.

This code, from the viewer pose's renderer, iterates over the pose's views and renders them. However, we have flags which, if true, indicate that a particular eye has been injured during gameplay. When rendering that eye, if the flag is true, that view is skipped instead of being rendered.

glLayer = xrSession.renderState.baseLayer;
gl.bindFramebuffer(gl.FRAMEBUFFER, glLayer.framebuffer);
gl.clearColor(0, 0, 0, 1.0);
gl.clearDepth(1.0);
gl.clear(gl.COLOR_BUFFER_BIT, gl.DEPTH_BUFFER_BIT);

for (const view of xrPose.views) {
  let skipView = false;

  if (view.eye === "left" && body.leftEye.injured) {
    skipView = updateInjury(body.leftEye);
  } else if (view.eye === "right" && body.rightEye.injured) {
    skipView = updateInjury(body.rightEye);
  }

  if (!skipView) {
    let viewport = glLayer.getViewport(view);
    gl.viewport(viewport.x, viewport.y, viewport.width, viewport.height);
    renderScene(gl, view);
  }
}

For each of the views, the value of eye is checked and if it's either left or right, we check to see if the body.leftEye.injured or body.rightEye.injured property is true; if so, we call a function updateInjury() on that eye to do things such as allow a bit of healing to occur, track the progress of a poison effect, or the like, as appropriate for the game's needs.

updateInjury() returns true if the eye is still injured or false if the eye has been restored to health by the function. If the result is false, indicating that the eye is now healthy, we render the scene for that eye. Otherwise, we don't.