Eyeglasses have prescription and non-prescription types, according to the lens power. Non-prescription eyeglasses utilize Plano lenses and are simply for eye beauty enhancement. However, there are a couple of different members in the prescription eyewear family. Nowadays, a large group of people living in this world have poor eyesight caused by various eye problems. Some are even blind. Vision is one of the most precious gifts granted by the god to human beings. Individuals who have unsatisfactory vision would always try hard to get their eyes treated. Until now, visual refractive errors are certainly the most common reasons for poor eyesight, and they bother a large portion of the world’s population. Another fact is that prescription eyeglasses in various forms are the major solution to refractive errors. Another common eye condition called presbyopia is also within the control of Rx eyewear. Aimed to deal with all these different eye conditions, prescription eyeglasses have different types. Single-vision glasses and varifocal glasses are two basic forms, a classification based on the number of lens focal points.
Single-vision glasses are actually a wide concept, which covers different forms of eyewear products. Indicated by the name, these prescription eyeglasses have Rx lenses that can deal with a single vision problem: myopia, hyperopia or presbyopia. This functionality is completely determined by the lens power. All people know that lens power determines the degree and the form of vision correction. A further explanation is that a lens used in single-vision glasses has only one focal point. This states clearly why their capability is restricted. But for patients who have only one of the vision problems listed above, single-vision glasses are certainly enough. For those beyond this group, varifocal glasses are the right option.
The fundamental difference between a single-vision pair and a varifocal pair is the focal points within a single lens. Different from a single-vision lens, a varifocal lens has more than one focal point. And according to detailed focal points, there are several types of varifocal eyewear. In detail, bifocal glasses have two focal points, trifocal glasses are made with three focal points and progressive reading glasses has a set of progressive addition focal points or powers. With the help of these forms of powerful lenses, varifocal glasses can deal with more than one vision problem within a single pair.