As a dog enters the clinic or examination room, the veterinarian will watch how the dog walks to look for any obvious signs of vision difficulties. The initial work-up will include an evaluation of pupil size and symmetry and an assessment of the dog’s pupillary light reflexes. The veterinarian probably will check the “menace reflex” by moving one hand swiftly toward the dog’s face, then stopping abruptly, checking for a blink reaction. Another test frequently done to detect vision deficiencies is to throw a cotton ball onto the floor while watching to see if the dog follows the movement. Blood and urine glucose levels will likely be assessed as well, to determine whether diabetes mellitus is a contributing factor to the dog’s vision problems.