Yes, that's pretty much what happens but there is a pattern to that initial scan. If you observe your eye travel over many images you will begin to notice the pattern. In a predominately dark scene your eye is drawn to the contrasting tone, in this case the small bright areas and in a light scene your attention is drawn to the small dark areas. From there you follow a pattern that you may repeat over and over, one element leading to the next. If you arrange your composition well the viewer's eye travel is always directed within the image in an easy path, like an oval, if you are less lucky a major leading line will guide the eye out of the frame and the viewer quickly loses interest in trying to get back into the image.It didn't feel like my eye read from left to right. If so it was very quick because my eye snapped instantly to the light.