Glass, plastic and polycarbonate are the materials most commonly used in the manufacture of eyeglass lenses. Prescription eyeglasses correct vision problems with different lenses and come in a variety of types. An optician will help you determine the type of lens best suited for your vision correction.
Glass is the original material used to make prescription lenses. Glass can break easier than plastic or polycarbonate materials and therefore must be manufactured to meet safety standards to protect the eyes under normal wearing conditions.
Most glasses today are made from plastic. Plastic lenses are less likely to shatter than glass and are flexible and lightweight. High-index plastic lens are thinner and flatter than conventional plastic lenses and are well suited for people with strong prescriptions as they reduce the thick appearance of prescription lenses required for large corrections. Polycarbonate lenses are recommended for eyeglass wearers who participate in sports. Polycarbonate is lighter than conventional plastic, impact-resistant and is considered the safest lens material.
Lens to Correct Myopia
Myopia, or nearsightedness, is a condition where you cannot see at a distance. Corrective lenses for myopia are thinner in the center, thicker at the edges and concave to bend light so that it reaches further back into the eye to attain the retina. If you are extremely myopic, high-index glasses are a good choice.
Lens to Correct Hyperopia
Hyperopia, or farsightedness, is a condition where you cannot see very close. Corrective lenses for hyperopia are thicker in the center, thinner at the edges and are convex to bend light to reach forward into the eye to attain the retina.
Lens to Correct Astigmatism
According to the Vision Council, astigmatism is a very common condition that causes blurred vision as a result of an irregularly shaped cornea. Corrective lenses for astigmatism alter the way light enters the eye.
You can obtain reading glasses with or without a prescription. These glasses contain single-vision lenses that improve near vision for farsighted people or those with presbyopia, which is a progressive condition associated with aging.
Multi-focal lenses provide distance and near vision correction without the need for two different pairs of eyeglasses. Bi-focal lenses correct distance vision on the upper portion and near vision on the lower. A tri-focal lens has an additional intermediate distance correction directly above the near vision correction. Some multi-focals have noticeable lines dividing each area of correction. Progressive lenses render the lines invisible and the distance and near corrections are blended in a gradual progression.
Lenses can be covered in a protective coating that reduces the incidence of coating. Though plastic lenses are less likely to shatter than glass, they are more prone to scratches. Scratch resistant lenses are an excellent option for children who may not be quite as careful with their eyewear as adults.
Drivers can benefit from anti-reflective lenses that help reduce glare and reflections. These lenses are coated with a substance allowing light to pass through, alleviating glare and reducing eyestrain. High definition lenses, available in free form and wavefront formats, also help to minimize glare.
Photochromatic lenses, also known as transition lenses, darken when exposed to sunlight and lighten indoors. They eliminate the need for separate sunglasses and provide UV protection from the sun, which can cause retinal damage, macular degeneration and photokeratitis, which is a sunburn of the eye.