This is a test of commonsense. Complete the next sentence:

How to know if your dog is losing its eyesight
Look for cloudy pupils.
When a dog's vision begins to suffer with age, you may notice a change to the eye color itself. Cataracts are often a cause of loss of vision related to age, and can be easily seen by looking at your dog's eyes.
Cataracts are marked by a cloudy appearance around a dog's pupil. Monitor your dog's eyes frequently as it ages, as cataracts are easier to treat and reverse if caught early.