Prescription eyeglasses and contact lenses are devices used to correct vision, specifically those which has something to do with refractive errors. These problems are all about the inability of the light bouncing off objects being observed to focus properly on the person’s retina. Both devices are prescribed by optometrists or ophthalmologists after examining the eyes.
Refractive errors can come in different forms. Nearsightedness or myopia causes a person to have difficulty in seeing far away objects. This is because the images focus before the retina. On the other hand, when the images focus behind the retina, the problem is called farsightedness or hyperopia. In this case, the person has trouble seeing things that are positioned very close to the eyes.
Another refractive error is called astigmatism. The person sees blurred images because of the cornea, the transparent covering of the front part of your eyes, is irregularly shaped. Together with the lens, the cornea helps in focusing light. Then there’s also a condition called presbyopia. This one also results in blurred images, but it’s related to aging.
Glasses are the most common forms of eyewear to correct many vision problem types. There’s a frame which sits on the person’s nose and ears, holding the lenses. The frame comes in practically any color, shape and size. Considered as the most durable material used is plastic, and it can come in acrylic, nylon, epoxy, polyamide, etc. It can also accommodate just about any type of prescription lens.
Metal frames are less noticeable than most plastic rivals. However, they’re also generally more expensive. They can come in stainless steel, nickel, titanium, titanium alloy, aluminum, silver, etc. Also there are rimless frames which are less noticeable and lighter in weight than both plastic and metal variants as the nosepiece and temples are attached to the lenses.
When it comes to the lens part, both glass and plastic ones may be used. There are different types available, depending on the vision problem. Concave ones are thin in the center part and are used for correcting nearsightedness. Convex ones are thick in the center, just like a magnifying glass, and are suited for correcting farsightedness. Cylindrical ones curve in one direction and are used for correcting astigmatism. There are also a variety of lens coating options available. Some of them include anti-reflective and UV protection coatings.
Directly worn over the cornea of your eye are contact lenses. They also work by correcting refractive errors, although in a very inconspicuous way. The optometrist or ophthalmologist will measure the curvature of a person’s eyes. He or she will also see if the eyes are too dry, or if there are certain problems which may prevent a person from wearing them.
There are varying types of contact lenses. They are rigid gas-permeable daily wear and extended wear lenses, soft lenses for daily wear and extended wear, disposable lenses and planned replacement soft lenses. While using them has some advantages, it may take some time getting used to wearing them. Also, it may not be able to correct some vision problems as well as eyeglasses, especially severe cases of astigmatism.