Most eyeglass wearers are near sighted, which requires corrective lenses that are thin in the center but thicker at the edge of the lens. The stronger the prescription, the thicker the edges (see lens drawings below).
Most of today's fashionable frames are made of plastic or metal with rims thinner than the lens itself. Also, popular rimless mountings mean that the edges of the lenses are completely exposed. In either case, the lens edges are highly visible, and thicker edges can detract from the appearance of your eyewear.
Eyeglass lenses correct refractive errors by bending (refracting) light as it passes through the lens. The amount of light-bending ability (lens power) that's needed to provide good vision is indicated on the eyeglass prescription provided by your optometrists.
Refractive errors and lens powers required to correct them are measured in units called diopters (D). If you are mildly nearsighted, your lens prescription might say -2.00 D. If you are highly myopic, it might say -8.00 D.
If you are farsighted, you need "plus" (+) lenses, which are thicker in the center and thinner at the edge.
Regular glass or plastic lenses for high amounts of nearsightedness or farsightedness can be quite thick and heavy. Fortunately, science allows the creation of a variety of new "high-index" plastic lens materials that bend light more efficiently.
This means less material can be used in high-index lenses to correct the same amount of refractive error, which makes high-index plastic lenses both thinner and lighter than conventional glass or plastic lenses.
FIRST EYESHOP ONLINE provides you the option of buying high index lenses.