What is a defining feature of progressive lenses?

Progressive lenses are uniquely designed to provide a smooth transition between multiple focal lengths, typically correcting for near, intermediate, and distance vision without the visible lines that are characteristic of bifocals or trifocals. This design allows wearers to see clearly at various distances, making progressive lenses particularly versatile for individuals with presbyopia or other vision changes that necessitate different lenses for different tasks, such as reading, using a computer, and driving.

The seamless transition in progressive lenses enhances comfort and usability, allowing for a more natural viewing experience as individuals change their focus from one distance to another. This eliminates the abrupt changes in vision that can occur with lenses that have distinct lines, thereby making daily activities more fluid and less disorienting.

The other aspects mentioned do not accurately characterize progressive lenses. They are specifically not defined by visible lines (which is a feature of bifocals), can require an adjustment period as wearers may need time to adapt to the different focal zones, and they are suitable for adults rather than being restricted to children.