Both bifocal and progressive reading glasses are considered multifocal lenses because they both offer more than one prescription power in one pair of glasses. However, despite this similarity, they are quite different from one another.
The lenses in bifocal glasses have two viewing sections: a larger, upper lens for distance viewing, and a smaller, lower lens for reading. There is a visible line where these lenses meet. Progressive lenses offer three viewing sections: a primary lens for distance viewing, a very slender midsection for intermediate distance vision correction, and a lower section for reading.
Unlike bifocal lenses, there is no visible line between the prescription lenses in progressive reading glasses. While this gives them a far more subtle appearance, it also creates a blurry section on the sides of the lenses, which can take some getting used to. Some people prefer bifocal glasses because there is no blurriness in the lenses, and consequently a wider line of sight.
The line between prescription powers in bifocals also contributes to an abrupt shift between magnifications that can be disorienting to bifocal wearers, especially on stairs. While progressive lenses don’t have such a dramatic shift between powers, it still takes a while for the eyes to adjust to a new pair of progressive reading glasses.
The middle distance visual correction offered by progressive lenses is a significant bonus for glasses wearers who use computers frequently. While bifocals are ideal for folks who need both distance and close-up vision correction, progressive glasses are a better option for those who frequently need middle-distance visual clarity.