Progressive glasses, also known as multifocal lenses, are a type of eyeglasses that have three prescriptions in one pair of glasses. They are designed to help people with presbyopia, a condition that affects the ability to see things clearly at different distances as they age. Progressive lenses have no visible lines, unlike bifocal and trifocal lenses, which have telltale lines in the lenses. The prescription changes gradually across the lens surface, providing a seamless transition between the different prescriptions.

Progressive lenses have three different levels of focal distances ranging from distance to near. They enable you to do tasks that require close-up vision, intermediate vision, and distance vision without swapping frames or taking glasses off. Progressive lenses are an update on bifocal and trifocal lenses, and they are sometimes called "no-line bifocals" or "no-line trifocals".

The advantages of progressive lenses include:

• Convenience: With progressive lenses, you wont need to have more than one pair of glasses with you. You dont need to swap between your reading and regular glasses.

• Natural vision: Vision with progressives can seem natural. If you switch from viewing something up close to something far away, you wont get a "jump" like you would with bifocals or trifocals.

• Seamless transition: Progressive lenses have a seamless look, and they do away with the old-fashioned lines found on bi- and trifocals.

However, progressive lenses also have some disadvantages. They can be challenging to find the sweet spot for certain distances when working on the computer or doing a lot of up-close fine print reading. Additionally, they have a learning curve, and youll have to train yourself to look out of the correct portion of the lens for the task you’re performing.

In summary, progressive glasses are a type of eyeglasses that have three prescriptions in one pair of glasses, designed to help people with presbyopia. They provide a seamless transition between different prescriptions and eliminate the need for multiple pairs of glasses. However, they also have some disadvantages, such as a learning curve and difficulty finding the sweet spot for certain distances.