Bifocal reading glasses are a special category of prescription glasses. The most outstanding feature of them is that one bifocal lens has two separate powers. The upper power is used to correct nearsightedness and the lower power is for presbyopia. Compared with single vision reading glasses, bifocal glasses can still offer vision correction for nearsighted individuals. This is the most widely recognized advantage kept by bifocal glasses. In fact, bifocal reading glasses differ from reading glasses only in lens power. Other factors such as eyeglass frame materials and lens materials are almost the same. For instance, there are available plastic frame bifocal reading glasses as well as metal frame ones. The difference is similar to other forms of glasses that plastic frame bifocal reading glasses are often slighter. This articles focuses on introducing shortcomings of bifocal glasses, including plastic frame ones.

A superficial problem associated with bifocal glasses is that there is a visible line usually sitting in the center of the lens horizontally. Even the newly developed designs including the D-segment have still visible line or lines for power separation. What is the concern? In an obvious way, these visible lines on the lenses are always telling other individuals that the wearer need reading glasses, which is resulted from presbyopia. This condition is always associated with aging, so that reading glasses are sometimes considered as the symbol of an old age. For most individuals who are still in their middle ages, such an obvious expression caused by visible lines is really unwanted. In addition, these visible lines will surely compromise the wearer’s charming look. From this viewing point, bifocal reading glasses are quite similar to trifocal ones.

A functional shortcoming of bifocal glasses is visual distortion. In some instances, new users of bifocal reading glasses need a few days to make an adaption. In serious cases, even headaches and dizziness will be caused. For certain individuals, these reactions even persist for a long time. In fact, these symptoms are caused by the two separated powers in a single lens. A power for nearsightedness and the other one for presbyopia are strictly and suddenly separated using the center line described above. Such an obvious separation or jump will cause some people to experience visual discomfort. In fact, another functional shortcoming is that bifocal reading glasses can not deal with computer tasks professionally. This factor can be resolved by trifocal glasses. All these mentioned shortcomings are equally true in plastic frame reading glasses.