Due to natural changes associated with age, your canine codger doesn’t have the eyesight he once did.
For example, that usually clear disc behind the pupil, the lens, becomes dense and cloudy with age. This is different from a cataract, which is an abnormality that can cause blindness. Your elderly dog may just have weaker vision for up-close objects. As a result, he might go downstairs more slowly or miss his usual sharp ball catches.
The retina, which captures and processes images, also changes with age. Cells that help your dog see in the dark start to thin out, so your pooch may be less eager to go out at night. Turning up the lights should help.
Once you make allowances for these changes, you can help your pooch with his shift in vision.