Bifocals eyeglasses, developed by Benjamin Franklin, are the combination of concave and convex lenses that are mostly prescribed to people suffering from presbyopia. This glass is clearly divided into two halves having two different types of lenses. The top lens is used for the distant viewing and the lower lens of the bifocal glasses is user for the reading purposes. Bifocal glasses are prescribed to people who require correction for hypermetropia, myopia and astigmatism. People suffering from presbyopia face problem in seeing nearby and distance object. Thus, rather having two pairs of glasses, bifocals glasses are the best choice that successfully addresses both the problems of presbyopia patients. In both the conditions of presbyopia the problem is that rays of light do not focus properly on the retina and to overcome this problem the corrective lenses are used. Corrective lenses properly focus the incoming light rays so that one can clearly see the nearby as well as distant object. Bifocal glasses are always compared with single vision reading glasses but it maintains its edge over the reading glasses as it provides vision correction for nearsighted patients. The main difference between the reading and bifocal glasses are in the power of the lens. All the other factors like frames and lens are almost same in both the bifocal and reading glasses as they are both made up of same material like metal and plastic. Visual distortion is the functional drawback of the bifocal glasses as new users of bifocal glasses require some time to get adapted and adjusted to this glass. Some patients might even face problem of dizziness and headache but this usually because this bifocal glasses have two separate powers in a single lens. This glass has power for both near sightedness and long sightedness that is separated by a visible clear line present at the middle of the glass. This sudden jump of the power can cause visual discomfort to some people. The visual discomfort problem sort out with the regular use of the bifocal glasses or else one can resolve it by using trifocal glasses. Visual distortion problem is common with both plastic bifocal glasses and the metallic bifocal glasses. But today many manufacturers have sorted out these problems in the bifocal glasses and have designed the bifocals that serve the both utility and style purpose of the users.
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