My son is 9 years old and has a swollen right eye ...

My son is 9 years old, and lately his right eye gets very swollen, this is not permanent, it happens out of nowhere, usually in the morning. What can it be? I'll take him to an ophthalmologist.
Expert answer:

It is hard to say exactly what it is, the most common causes are vision diseases that need correction or allergic or inflammatory eye diseases, the vast majority are not serious diseases and are easily treated. Taking him to the ophthalmologist is really wise.