Benefits from high-index lenses
Thin eyeglasses bring attractive appearance and light ones bring comfort. Thinner and lighter high-index lenses are the perfect choice for wearers who pursue these features. A common sense is that lenses for myopia correction are thicker at the edge and thinner at the center. Stronger prescriptions require thicker lens edges. With the prevalence of rimless and semi-rimless eyeglass frame styles, those conventional plastic or glass lenses’ thick edges are even more obvious, which can detract from the eyeglass appearance.
The prescription of a lens is determined by the amount of light refraction that your myopic eye need. A higher prescription requires the lens to bend more light to provide clear vision. For instance, a person with a prescription of -5.00 diopters needs more light refraction than an individual with a -2.00 prescription. And stronger minus lenses require thicker lens edges. In fact, myopia in most people progresses as they age, which means the lens edge will also grow in thickness.
High-index materials can bend light more efficiently, making myopic lenses have thinner edges than that of conventional plastic lenses with the same prescription. This efficiency reduces the materials that are used in high-index lenses, while ensuring enough myopia correction. Thinner lenses in turn decrease the overall weight of the lenses, so that high-index plastic lenses are lighter than conventional plastic lenses with the same vision correction effect. High-index lenses can also benefit from an aspheric lens design, which makes them flatter and enhance their appearances.
High-index materials have different “index of refraction”. Lens materials with higher refractive indexes can make the lens thinner, which explains why high-index lenses are thinner. Conventional plastic has a refractive index of 1.50, and that of glass is 1.52. High-index plastic and glass are now available with refractive indexes between 1.53 and 1.74. Lenses made of high-index materials are thinner than that made of low-index materials. It is estimated that a lens with a 1.70 index can be at least 50% thinner than a conventional plastic lens.
In fact, only high prescriptions require high-index lenses, and the highest index materials are usually for the strongest prescriptions. You should evaluate your prescription needs in deciding proper high-index materials, since higher index lenses cost higher fees.
High-index lenses with anti-reflective lens coatings can transmit 99.5% of the light, reducing light reflection from the lens surface. As a result, visual clarity can be ensured, which is advantageous for night driving. Reflection reduction even makes high-index lenses appear thinner.
Article Source:http://vision.firmoo.com/eyeglasses/benefits-from-high-index-lenses.html
The prescription of a lens is determined by the amount of light refraction that your myopic eye need. A higher prescription requires the lens to bend more light to provide clear vision. For instance, a person with a prescription of -5.00 diopters needs more light refraction than an individual with a -2.00 prescription. And stronger minus lenses require thicker lens edges. In fact, myopia in most people progresses as they age, which means the lens edge will also grow in thickness.
High-index materials can bend light more efficiently, making myopic lenses have thinner edges than that of conventional plastic lenses with the same prescription. This efficiency reduces the materials that are used in high-index lenses, while ensuring enough myopia correction. Thinner lenses in turn decrease the overall weight of the lenses, so that high-index plastic lenses are lighter than conventional plastic lenses with the same vision correction effect. High-index lenses can also benefit from an aspheric lens design, which makes them flatter and enhance their appearances.
High-index materials have different “index of refraction”. Lens materials with higher refractive indexes can make the lens thinner, which explains why high-index lenses are thinner. Conventional plastic has a refractive index of 1.50, and that of glass is 1.52. High-index plastic and glass are now available with refractive indexes between 1.53 and 1.74. Lenses made of high-index materials are thinner than that made of low-index materials. It is estimated that a lens with a 1.70 index can be at least 50% thinner than a conventional plastic lens.
In fact, only high prescriptions require high-index lenses, and the highest index materials are usually for the strongest prescriptions. You should evaluate your prescription needs in deciding proper high-index materials, since higher index lenses cost higher fees.
High-index lenses with anti-reflective lens coatings can transmit 99.5% of the light, reducing light reflection from the lens surface. As a result, visual clarity can be ensured, which is advantageous for night driving. Reflection reduction even makes high-index lenses appear thinner.
Article Source:http://vision.firmoo.com/eyeglasses/benefits-from-high-index-lenses.html
Source...