Now in order to become both a confident and competent optician, we must first understand the different types of lenses that are available and how they can help us enhance our patients lives.So, let's start with the basics.
First, we have a single Vision lens. A single vision lens is defined as one that has one distinct power for a patient to see clearly at one specific distance throughout the entirety of the lens. Now for those of us that are under 40 years old or non-presbyopic patients, we can put on those glasses and see clearly from far away to up close. No matter what we're looking at through that same prescription. But as our eyes age, we actually lose the focusing power in our eyes and that single vision lens truly only works for one single distance. So whether that be a distance pair that our patients actually see better when they take off their classes for up close or whether we turn that into a pair of reading glasses so that they can read a book or maybe just a pair for computer vision so that we see more clearly when we’re looking at our work all day long.
Next we have a bifocal. A standard bifocal lens actually has two distinct powers of a lens. Hence the name of a bifocal. Normally this is used as a pair of glasses that in the top has distance or every day viewing but, in the bottom, you’ll actually see a segment on the front of that lens that's actually focused for near vision so someone can see far away and up close. This is probably the most traditional lens that you see on people that need help with the focusing power of their eyes.
Next we have a trifocal and just like the name indicates, tri stands for three. which means this lens has three distinct powers or prescriptions in it for different viewing points. The top or main portion of the lenses is for everyday viewing, for looking far away. The middle portion that you see on the lens that looks like a rectangle segment right on the middle of the lens there is actually for intermediate or arm’s length. So usually that's our computer or the dash of our car.Finally, in the bottom of the segment, just like in the bifocal that's meant for our reading vision or for our up close and near vision.
Finally, we have a progressive lens. Now these are called PAL’s. P-A-L which stands for Progressive Addition Lens. Some people call them no line bifocals, but that term is actually not correct because what this actually does is provides clear vision from far to near in all one lens without having just chunks of vision segmented on the lens. You can see clearly from far to near as best as possible without having the segments visible on the lens.