I get blurry vision and feel lightheaded occasionally?

At some points during the day, I will feel lightheaded and get blurry vision. This will go on for around 8-9 seconds before I'm back to normal, sometimes longer. I doubt it is to do with my diet since I eat enough and healthily, and I drink plenty of water. It happens randomly, and not just during specific times such as when standing up.
I currently wear glasses and had an eye exams a few months ago