Noise sensitivity may develop as a result of an abnormality in the middle or inner ear. Trauma to the ear may cause noise sensitivity. Noise sensitivity may be present with migraine headaches. Noise sensitivity may occur as a side effect of certain medications. Noise sensitivity may occur as a result of an ear infection. People with misophonia find it impossible to tolerate certain sounds.
Equal division lenses, segmented bifocals and blended lenses â also called seamless or invisible bifocals â are three main types of bifocals. Equal division bifocal glasses feature lenses cut in two distinct halves, with the magnification part on the lower half and the long-distance lens on the upper half. The initial version of the equal division lenses, called the executive cut, had a visible horizontal line directly across the lens.
The business of manufacturing eyeglass frames and lenses made its most dramatic leap in the twentieth century with the rise of plastics. Plastic lenses are lighter in weight and can be manufactured as bifocals, trifocals, and quadrifocals to correct a wider range of vision problems.