The prescription eyeglasses offer a variety of lenses. These lenses include; high-index lenses, progressive lenses, multifocal lenses, and single vision lenses. All of these lenses have distinctive properties which cater to the individualized needs of every patient. Let’s take a detailed look at each of these lens types.
High Index Lenses
High-index lenses are by far the most advanced form of lenses available. These lenses have the highest refractive index due to which they have the highest power of bending the light to correct the refractive errors of the eye.
Doctors usually prescribe these lenses for patients who require strong correction for myopia i.e. shortsightedness and hyperopia i.e. long-sightedness, along with light and thin lens material.
High-index lenses have thinner edges as compared to conventional lenses with similar prescription power. These lenses are also light in weight as less lens material is used for their formation because of thinner edges of these lenses, and this reduces the total weight of these lenses. Because of being lightweight, these lenses are a source of great comfort for such patients who need to wear their glasses at all times.
Progressive lenses are popularly called as ‘no-line bifocals’ because they eliminate the highly visible lines of the conventional multifocal lenses. One of the major advantages of these lenses is seamless progression of different power lenses meant for viewing objects at all distances. Patients usually prefer these lenses over multifocal lenses for the correction of presbyopia because of better quality vision.
The ‘image jumping’ problem is a common issue with multifocal lenses. This means that as the patient’s eyes are moved through the sharp boundary between the distant and near parts of the lens, the image seems to jump. This is because the lenses of different power present with a single multifocal lens don’t possess a smooth and seamless transition. Whereas, there’s absolutely no image jumping in case of progressive lenses because of perfectly seamless lens progression.
There are two types of multifocal lenses i.e. bifocal and trifocal lenses. Bifocal lenses contain two lens powers to correct distant and near vision when the focus can’t be changed naturally by the eyes because of different factors such as age, exposure to harmful radiations, and more. Trifocal lenses are an advanced form of bifocal lenses as they contain three lenses to correct the vision.
These lenses are prescribed to correct a common vision disorder ‘presbyopia’. In this condition, the patient experiences blurred near vision during reading, sewing, or using the computer. This condition becomes quite apparent after a person crosses the age of 40. In addition to this, multifocal lenses are also used as a tool to prevent the onset of myopia in those children and teenagers who use computer and smart phones quite excessively.
Single vision lenses are the most conventional lenses used to treat the vision defects like myopia, hyperopia, and astigmatism by converging or diverging the light ways entering the eyes, so that they strike the right spot of the eye’s retina. The light rays don’t fall on the right spot of retina because of the compromised refractive power of the eye’s lens. The single vision lenses correct this refractive power of our eyes which results in a clear image. However, these lenses are not very effective in correcting the refractive index after the age of 40, hence, they’re usually replaced by multifocals, progressive, or high-index lenses.
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