Lined bifocal and trifocal lenses are the next step from single-vision lenses and correct multiple distances. Bifocals are commonly used for individuals who require correction for distance and close vision, such as those who need glasses for reading and driving. Bifocal lenses have two prescription strengths in one lens, with a visible line separating the two correction areas. The top part of the lens is for distance vision, and the bottom portion is for near vision.
On the other hand, Trifocal lenses have three prescription strengths in one lens, with two visible lines separating the areas of correction. In addition to the distance and near correction, trifocal lenses provide intermediate vision correction, which is helpful for individuals who require correction for activities such as computer use.
Both bifocal and trifocal lenses are available in various materials, including plastic, polycarbonate, and high-index plastic. They can also come with lens coatings for added performance and protection.
However, one of the drawbacks of bifocal and trifocal lenses is the visible line or lines, which can be aesthetically unappealing to some individuals. In addition, the line or lines can also interfere with the visual field, making it difficult to see objects at intermediate distances.
Progressive lenses, also known as no-line bifocals, provide a more seamless and aesthetically pleasing solution for individuals who require correction for multiple distances. Progressive lenses gradually change prescription strength from distance to near, without the visible lines found in bifocal and trifocal lenses.
In conclusion, bifocal and trifocal lenses correct multiple distances, while progressive lenses offer a more aesthetically pleasing and functional solution for individuals who require correction for various distances. The best lens solution will depend on individual needs and preferences, and an optometrist can help determine the best option.