Benefits from high-index lenses
Article Tags: high-index lenses
Thin eyeglasses bring attractive appearance and comfortable experience. Thinner and lighter high-index lenses are the perfect choice for wearers who are aware of both appearance and comfort. 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.
Thinner and lighter high-index lenses
The prescription of a lens is determined by the amount of light refraction the myopic eyes 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 that 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 of 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 appearance.
Improvement or enhancement made by high-index lenses in terms of visual aid and wearer appearance may also be contributed by the application of an anti-reflective coating. While traditional lenses bend about 8% of the light entering the eyes, regular high-index lenses bend 50% more. It is amazing that high-index lenses applied with an anti-reflective lens coating can transmit 99.5% of the light, reducing light reflection from the lens surface. As a result, visual clarity can be ensured and a sharper vision will be brought. For people involving much night driving, this visual improvement is meaningful. In addition, reflection reduction even makes high-index lenses appear thinner, and thus enhance facial beauty.
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 indices 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 power of prescription requires high-index lenses, and the highest index material is usually for the strongest prescription. You should evaluate your prescription needs while choosing a proper high-index material, since higher index lenses equal to higher fees.
A comparison between polycarbonate and high-index lenses
It is widely known that polycarbonate lenses are much lighter and thinner than regular plastics. They also feature natural 100 percent UV protection. What’s more, these lenses are up to 10 times more impact-resistant than regular plastic lenses. In detail, high index lenses with a refraction index of 1.70 are typically 50% thinner than traditional plastic lenses. Due to their common improvement in lens thickness, polycarbonate and high-index lenses nearly offer the same aesthetic benefits. But polycarbonate lenses are more frequently associated with visual distortion and lens scratches. It is also more difficult for opticians to apply lens coatings and tints to polycarbonate lenses. In other words, high-index lenses perform better in these aspects.