Safe and effective!
To avoid the UV's side effects, sunglasses are more important than adults. Because the baby's pupils are relatively bigger, the lens is transparent, and is likely to be damaged by the sun light. Parents must pay attention to protect baby's eyes and choose high-quality sunglasses. If wearing toy sunglasses or other plastic lens of fake one, kids' eyes cannot be protected correctly, on the contrary, the pupil will be expand in the sun, more lights into retina, and cause refractive errors (myopia or hyperopia) and amblyopia.
If you wanna your kids wear sunglasses, choose the good one. Otherwise, not wear it. When kids go out, umbrella and hat can also prevent the sun light into their eyes.