Ever wonder what you’re supposed to put in the “PD” box when you’re entering your prescription online? Pupillary distance (PD) is the distance between the centers of the pupils of your eyes, and it’s used to determine the proper lens shape and alignment of your prescription to your line of vision.
If you've ever experienced an eye twitch—or spasm—you know it feels like the whole world can see that your eye is flickering out of control at what feels like the same pace as a hummingbird's wings. Most of the time this quivering sensation is barely noticeable to the people around you, and it ends as quickly as it begins. But, not all eye twitches are the same, and some symptoms need closer attention.