Last updated on April 14th, 2017 at 02:53 pm
High-index eyeglass lenses are the right option if you desire thinner, lighter lenses and eyeglasses that are as attractive and comfortable as possible.
What You Should Know about High Index Lenses
Thinner, lighter high-index lenses are specifically suggested if you have a strong spectacles prescription for nearsightedness, farsightedness or astigmatism.
Many eyeglass wearers are nearsighted, which requires corrective lenses that are thin in the center however thicker at the edge of the lens. The stronger the prescription, the thicker the edges.
Most of today’s fashionable frames are made from plastic or metal with rims thinner than the lens itself. Also, popular rimless mountings suggest that the edges of the lenses are entirely exposed. In either case, the lens edges are extremely noticeable, and thicker edges can diminish the appearance of your eyeglasses.
How High-Index Lenses Differ From Regular Lenses
Eyeglass lenses proper refractive errors by flexing (refracting) light as it passes through the lens. The quantity of light-bending ability (lens power) that’s had to supply excellent vision is indicated on the glasses prescription offered by your optometrist.
Refractive mistakes and lens powers needed to remedy them are measured in systems called diopters (D). If you are mildly nearsighted, your lens prescription may say -2.00 D. If you are extremely myopic, it may say -8.00 D.
If you are farsighted, you require “plus” (+) lenses, which are thicker in the center and thinner at the edge.
Regular glass or plastic lenses for high quantities of nearsightedness or farsightedness can be quite thick and heavy. Fortunately, chemists have developed a variety of new “high-index” plastic lens products that bend light more effectively.
This implies less product can be used in high-index lenses to remedy the same quantity of refractive error, makings high-index plastic lenses both thinner and lighter than traditional glass or plastic lenses.
Benefits of High-Index Lenses
Thinner. Since of their ability to bend light more efficiently, high-index lenses for nearsightedness have thinner edges than lenses with the very same prescription power that are made from conventional plastic material.
Lighter. Thinner edges require less lens material, which lowers the general weight of the lenses. Lenses made of high-index plastic are lighter than the same lenses made in traditional plastic, so they’re more comfortable to wear.
High-index glass lenses likewise have thinner edges, but high-index glass is heavier than traditional glass, so there is not as much weight savings with glass as there is with plastic lenses.
Light-weight lenses are even more of a benefit for farsighted prescriptions, which can make standard lenses very heavy. And a lot of high-index lenses also have an aspheric style, which gives them a slimmer, more appealing profile and reduces the magnified “bug-eye” look that standard lenses cause in strong farsighted prescriptions.
See also: LASIK Risks And Complications
Lots of High-Index Lens Choices
There is a wide range of thin, lightweight high-index eyeglass lenses, based upon how efficiently they bend light.
The light-bending capability of glasses lenses is figured out by the “index of refraction” of the lens material. This refractive index is the ratio of the speed of light when it takes a trip through air to the speed of light when it goes through the lens product.
The speed of light is lowered the more it is refracted as it passes through a lens material. Therefore, lenses that bend light more effectively have a higher index of refraction than those that bend light less efficiently, and lenses with a higher refractive index are thinner than lenses of the same power made of materials of a lower refractive index.
In short: the greater the refractive index, the thinner the lens.
Conventional plastic lenses have a refractive index of approximately 1.50. For glass, it’s 1.52. Any lens product with a refractive index that’s greater than that of glass or plastic is considered to be high-index.
High-index plastic lenses are now offered in a wide variety of refractive indices, usually varying from 1.53 to 1.74. Lenses with an index of refraction of 1.70 or higher normally are at least 50 percent thinner than standard plastic lenses.
Also, normally speaking, the higher the index, the higher the cost of the lenses.
Your glasses prescription also determines what sort of high-index product you may desire for your lens. The highest index materials are used primarily for the strongest prescriptions.
If you want high-index lenses, make sure to request them. However count on your optometrist’s or optician’s guidance regarding which index to use. Your eye care practitioner can describe which high-index lenses are the best option for your requirements and spending plan.
The majority of today’s popular lens styles and functions (single vision, bifocals, progressive, photochromic, etc.) are available in high-index materials. But there are exceptions, so ask your optometrist or optician for details.
Also read: Proper Glasses for Computer Use
AR Coating: A Perfect Companion for High-Index Lenses
All lens products obstruct some light from passing through the lens. This light shows back from the lens surface, causing diversions and minimizing the clearness of night vision.
Conventional glass or plastic lenses reflect about 8 percent of light that otherwise would reach the eye. High-index lenses reflect up to 50 percent more light than standard glass or plastic lenses.
For the best vision and appearance, it’s a good idea to have an anti-reflective lens coating (AR coating) applied to high-index lenses. AR-coated high-index lenses transfer approximately 99.5 percent of light to the eye for maximum vision.
And because AR coating practically gets rid of lens reflections, it makes high-index lenses appear nearly invisible, so others see your eyes, not your lenses.
Likewise, research studies have shown that glasses lenses with anti-reflective finishings provide sharper night vision with less glare — a real benefit for night drivers.