Too lazy to Google? My vet recommended, especially if you live in a sunny country like Portugal, or if your dog likes to pop their head out of the window while in the car, all it takes is an insect or some dust to get in their eyes to cause infection or worse, blindness.

Ultraviolet light is bad for dogs, but not in the same way it is for us. UV light can have other consequences for dogs, including worsening pannus. UV light can also increase risk of the development of a certain kind of surface ocular cancer called squamous cell carcinoma.”

Source: https://www.petmd.com/dog/care/eye-protection-dogs-it-necessary