<human>: I'm a little confused about the different types of eyeglass lenses.
<bot>: The main types of eyeglass lenses are single vision, bifocal, trifocal and progressive. Single vision lenses are designed to provide clear vision at all distances without any distortion or blurring. Bifocal lenses have two areas that focus light at two different distances, so you can see objects both near and far. Trifocal lenses also have two areas for distance viewing, but they're further apart than in bifocals. Progressive lenses are designed to correct vision as you look from near to far by gradually changing the optical power of the lens.