Eyeglasses come in a variety of types specific to their uses. Prescription eyeglasses enable correction of visual problems with various lenses, which distinguish eyeglass types. Tinted eyeglass lenses shield your eyes to protect them from sun damage. When used for sports or in hazardous occupations, eyeglasses protect your eyes from accidental injury.
Single-vision lenses correct distance vision for problems such as myopia, which causes difficulty with distance vision, but enables you to focus more clearly on near objects. With hyperopia, near objects are blurred while distant objects remain clear. TLC Laser Eye Centers says that presbyopia occurs between 40 and 50 years of age and causes difficulty when attempting to read small print.
The American Optometric Association describes astigmatism as a common condition that causes blurred vision as the result of an irregular-shaped cornea or lens. Correction of this condition, as well as other visual impairments, requires eyeglass lenses that alter the way light enters the eyes.
Multifocal lenses correct distance and near vision without the need for two separate pairs of eyeglasses. Three types of multifocal lenses provide different methods of correction, according to the health resource website Eyes and Vision. The upper portion of a bifocal lens corrects distance vision while the lower portion of each lens corrects near vision. Trifocals add an intermediate distance correction directly above the area of close vision correction. Bifocals and trifocals have a noticeable line dividing each of the areas of correction. Progressive lenses smooth the line rendering it invisible as you make the transition through the three stages of distance correction.
The weight of glass lenses made the need for greater degrees of correction necessitate the use of thick, heavy lenses. The development of plastic lenses alleviated this problem. The flexibility and lightweight of plastic lenses make them less vulnerable to shattering. High-index plastic lenses reduce the thick appearance of lenses for prescriptions requiring a large amount of correction.
Impact-resistant polycarbonate lenses provide protection for eyeglass wearers who participate in sports and people engaged in other hazardous activities or employment.
Other Types of Eyeglass Lenses
Protective coatings help reduce eyestrain caused by reflective glare. Another special coating protects eyes from damage caused by ultraviolet rays. UV coating protects the eyes of patients following cataract and other types of eye surgery and people taking medications that increase light sensitivity. It also provides protection for children and workers in occupations that require them to spend a lot of time outdoors, according to Chancellor Eye Care.