Abstract: An examining device is provided which quickly and easily determines the "sidedness" of an individual's eyes. The device has a viewing port and conical opaque sidewalls which converge to a small diameter viewing port. The device is constructed so that the individual being tested can see with both eyes an object just beyond the end of the viewing port, but cannot see with both eyes an object which is relatively further away from the viewing port. A first blocking device is provided for alternatively blocking and unblocking the right eye line of sight of the person being examined. A second blocking device is provided for alternatively blocking and unblocking the left eye line of sight of the person being examined. The device is used by asking the individual being examined to look through the device to an object which is located relatively far beyond the end of the viewing port. While the device is held steady, the first blocking device is used to block the right eye line of sight.