You didn't mention your age but there is a definite link between aging and loss of balance. Muscle weakness and deconditioning are often part of that process. These two factors lead to decreased balance, especially when standing on one leg.

Other visual changes besides visual acuity may also factor in. For example, seeing the edges of surfaces (where one surface ends and another begins) gets blurred over time. This skill is called contrast sensitivity. If your dog's fur blends in with the color of the carpet or floor, you may not see her in time to avoid her.

The ability to make quick adjustments to avoid obstacles also decreases as we age. So even if you see the dog, you may end up running into it, stepping on it, or tripping over it because your reaction time is too slow.

Studies show exercise is still the best way to combat some of these changes that come with aging. T'ai Chi, a form of the martial arts has become very popular with older adults. It focuses on making slow, smooth movements. Tai chi is an excellent way to work on coordination and balance at any age.