hello, last week I got eyeglass what purchased from online shop, but this glass is not uniform across the bottom or across the top. Why is this? I have to move my head all around to get vision on the bottom and I can't move my head to one side on the top part or the clarity gets worse. I have another set of glasses (from the local shop) with the same exact prescription and I see clearly all the way across the lense. Maybe something is not right. Why these are different?