● The advantanges of the 1.56 index.
----Hardness: One of the best quality in hardness and toughness, high impact resistance.
----Transmittance: The highest transmittance as compared with other index lenses.
----ABBE: The highest ABBE value providing the most comfortable visual experience.
----Consistency: The most reliable and consistent lens product physically and optically.
● What is the RT-28?
RT-28 lenses has two different lens powers that aid in seeing objects at various distances once the aging process reduces your ability to do so. These are usually prescribed to adults older than 40 years, although some children and younger adults may also need them for focusing problems, which strain the eyes while reading.
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Whatever the reason one might need to obtain prescription for correction of near-vision, bifocals work similarly. That is, the small lower lens segment (also called "seg") has the refractive power you require to correct near vision while the other part of the lens works for distance vision.
In using bifocals, you would look through the upper part of the bifocals to focus on farther objects and look down through the lower segment to read or focus on objects at a distance of 18 inches or less.
● Tips of wearing the bifocal lenses.
A simple way of wearing bifocals, is to put them on and focus for distance through the upper segment, then, without moving the head (this is most important—no head movement) to lower the eyes to read a book held 18" away and down at an angle of 30 degrees. One thus uses the lower segment for reading. This exercise must be repeated over and over again so that the brain and the eye adapt to a new system of reading.