Sometime today, preferably during a quiet moment, look out across a familiar outdoor scene. Maybe your back yard or the view from your office window. Notice any small movements in your field of vision and focus in on the movement. What do you see? Then, in the overall scene, write down all the visual details that you can identify: quality of light, color, contrast, etc. (You can use this list of visual submodalities to prompt you). Come back to this scene later in the day and write down any differences.
See if you can find other ways to sharpen your visual acuity.