Yes, it is normal for little child wearing glasses. And there is no age limits for wearing glasses. If the child suffers from strabismus, amblyopia or myopia, it is normal to buy prescription eyeglasses to help them to see clear. In fact, some vision problems like nearsightedness will be inherited from parents. So, it is normal to child at 4 to wear eyeglasses.
There is no standard age for children to wear glasses. So, at any age if the child suffers from version problems such as astigmatism, hyperopia or myopia can wear glasses. So, the first thing you need to do is make sure that whether your child has these vision problems. If he has, just take him to the optician, and fill him a pair of glasses according to his prescription. Or his eyes will always in a sate of weary, and this will make his vision worse. But this is not the only thing you can help with him, you should pant more green plants at your house, and make a good environment for him. So, it is normal for your 4-year-old child wearing glasses.
Children's visions before six years old are developing. If it is little refractive error, or pseudo myopia, you can consider not to have lenses or eyeglasses for your child.
If your child do eye exercise everyday and regular inspection, the majority of children's sight can be back to normal.
At ordinary times, you should pay attention to children's television time control, one time one half.
Let children to take part in outdoor sports, it can alleviate the eye fatigue after learning, and sports itself also can promote the eye muscles' development of the structure, the child body and mind, and it is not only good for their bodies, but also their visions. Regular vision inspection every six months or a year is important. In this way, you can know whether children have myopia, farsightedness, astigmatism, amblyopia or not. Early corresponding treatment can prevent your child from refractive error in time.