I see waves of black spot going inward to where i am looking at appears after 5 second.it starts small then gets bigger.i tend to only see it on hot&sunny days.goes away when i look elsewhere i have astigmatism.doc say reduce screentime, eye strain?

While floaters can be benign, seeing an object in your visual field requires a dilated eye exam to exclude any serious pathology, though not likely in a healthy 13-year-old. A history of trauma or migraine is important. Eye strain and prolonged screen time is not a cause for floaters. You may need glasses, and have a vitreous opacity. See an ophthalmologist.