Spectacle 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 spectacle prescription provided by your optician.
Refractive errors and lens powers required to correct them are measured in units called dioptres (D). If you are mildly shortsighted, your lens prescription might say -2.00 D. If you are highly myopic, it might say -8.00 D.
If you are longsighted, you need "plus" (+) lenses, which are thicker in the centre and thinner at the edge.
Regular glass or plastic lenses for high amounts of shortsightedness or long sightedness can be quite thick and heavy.
Fortunately, manufacturers have created a variety of new "high-index" plastic lens materials that bend light more efficiently.
This means less material can be used in high-index lense to correct the same amount of refractive error, which makes high-index plastic lenses both thinner and lighter than conventional glass or plastic lenses.
Advantages of high-index lenses
Thinner
Because of their ability to bend light more efficiently, high-index lenses for shortsightedness have thinner edges than lenses with the same prescription power that are made of conventional plastic material.
Lighter
Thinner edges require less lens material, which reduces the overall weight of the lenses. Lenses made of high-index plastic are lighter than the same lenses made in conventional plastic, so they're more comfortable to wear.
And most high-index lenses also have an aspheric design, which gives them a slimmer, more attractive profile and reduces the magnified look that conventional lenses cause in strong longsighted prescriptions.
High-index lens choices
High-index plastic lenses are now available in a wide variety of refractive indices, typically ranging from 1.60 to 1.74. Lenses with a refractive index of 1.60 & 1.67 can be at least 20 percent thinner than conventional plastic lenses, and 1.71 or higher typically can be around 50 percent thinner.
Also, generally speaking, the higher the index is, the higher the lenses cost.
Your spectacle prescription also determines what kind of high-index material you might want for your lens. The highest index materials are used primarily for the strongest prescriptions.
Most of today's popular lens designs and features — including Dual Aspheric, Progressive, Bluecut Pro, Prescription tinted, and innovatively Spin-coating photochromic lenses— are available in high-index materials. Welcome to click into our pages on https://www.universeoptical.com/armor-revolution-product/ to check more details.