Hi, I'm Dr. Jim Kirkconnell of Bellevue Eye Care Center, in Nashville, Tennessee. We have a question that what are the different types of lenses? Now, we're not talking about the materials. We're talking about how they function. We can have a set of glasses that is just for distancing. If a person is near-sighted then or myopic then typically that person can read up close without any problem, but the far away is blurry. And that's called a single vision lens because it's for one particular distance. Now, the opposite is when somebody has good distance vision but they have presbyopia and they are past the age of forty or forty five typically, and they have difficulty seeing up close, and so they can have glasses which are single vision for reading. If they have them on and they they look far away it will be blurry, but if they look over the top which... For instance, if I put on my pair, look over top like this you see fine, and then if you have the whole thing for reading everything is clear through here but the far away is going to be blurry. The other type of lens is a progressive lens which is frequently called a no line. That is what this pair actually is where the the top part is for distance, and then as you go down there's a channel where things will be in focus closer and closer and there's a bottom window in order to see. The advantage of this type is that there's no line, that when you walk you don't see a line. When you drive you don't see the line, and cosmetically it's more appealing. We look younger. Its disadvantage is that typically you have six or eight inches of width to see, and you have maybe five to seven inches of depth to see which is not as good as this other pair. And that is this one which is this is called a flat top bifocal. It's the one that looks like a half moon on its side, and the top part is for distance and then the bottom window gives me about fifteen inches of width to see which is which is a a better range of vision on the up close and and more depth. And then, the other thing that's different about this type of glass is if I get outside of that half moon the floor is clear and there's no distortion. With the type that is the progressive even in the very best ones that we have in the fourth generation today, because there's a a steeper grind done on the bottom part the further down that we go where my hands are is not clear. It's it's a bit blurry. And that's the nature of progressives, that you don't have a a clear floor. That being said, if someone truly needs a bifocal then ninety percent of the time they get the progressive, and ten percent of the time they get the line type. That is either because they prefer it that way one way or the other, or you know, the bifocal with the line is certainly more economical. So, those are the three types of glasses that we have.
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