Sensory adaptation is a very incredible process of the body. It is the way our body adapts to new experiences, or diminished sensitivity as a consequence of constant stimulation. The way you adjust to smell, touch, and sound are all covered by sensory adaptation. For example, when you first get into a pool, and it's freezing cold. In a few minutes, the water becomes nice and you forget about the temperature altogether.
For eyesight, however, sensory adaptation is different. Why is it that after staring at something for a long period of time, we continue to see it? The object doesn't disappear because our eyes are in constant movement. However, with new instruments created by psychologists, we can find out if these sights would vanish if the eye's movement stops.
But back to the point. Sensory adaptation focuses our attention on changing stimulation because as the eye continues to be stimulated, we don't get used to the image we perceive, so to speak.
Although sensory adaptation reduces our sensitivity, it offers an important benefit. it enables us to focus our attention on informative changes, without being distracted by other stimulations of the senses in the environment around us.