A Science Lesson in How Contacts Correct Vision Problems
Contact lenses have become an increasingly popular alternative to glasses for correction of visual problems. With their ease of use and their ever-increasing level of comfort, it is easy to see why so many people have turned to contact lenses to help them see. In addition, most people find themselves to be more attractive looking when wearing contact lenses and prefer to wear them while engaging in sports. But, how exactly do contact lenses help improve site and what are the differences between the many types available?
The Miracle of Contact Lenses
For those individuals with visual problems, there is a problem between the length of their eye and its refractive power. As a result, the eye experiences a refractive error. A refractive error is a problem in which the eye fails to focus light properly. As a result, the person has decreased visual acuity, or the ability to see clearly. The contact lens helps correct this problem by focusing the light properly onto the retina. As a result, contact lenses are capable of correcting the vision of those with myopia (near sightedness), hypermetropia (far sightedness), presbyopia, and astigmatism.
More specifically, a person will experience “perfect vision” when rays of light are capable of meeting at a point directly on the retina, which is located on the back of the eyeball. Unfortunately, only about 40% of people have eyes that successfully perform this task. For the remaining 60%, proper vision must be achieved by refocusing the light within the eye.
Contact lenses, which are held in place by the natural tears created by the eye, form a thin layer over the eye to assist with refocusing. For those who have myopia, the problem is with seeing objects at a distance. The contact lenses prescribed to patients with myopia, therefore, are concave. This helps to properly refocus the light onto the retina. A patient with hyperopia, on the other hand, has difficulty seeing objects close up. Therefore, convex contact lenses are used to help redirect the light in their eyes.
For those with astigmatism, the problem is a little different. An irregularly shaped cornea characterizes astigmatism. Therefore, the light entering the eye is focused on two separate points within the eye. Originally, contact lenses were unable to assist those with astigmatism at achieving better vision. New “toric” lenses, however, have been developed to help improve the vision of those with astigmatism, as well.
Toric lenses are different from traditional spherical contact lenses, which have the same power of correction throughout the lens. A toric contact lens, on the other hand, has varying powers of correction throughout the lens. These special contact lenses actually have two different powers to them and are designed to stay in place regardless of eye movement. In fact, they are often weighted in an area to help keep them in place. Some have tiny marks on them to help the wearer determine the proper way to place them in the eye while others are designed to reset themselves properly when the wearer blinks.
Presbyopia, which is the natural aging of the eye and resulting loss of sight, makes it difficult for the patient to shift from viewing far objects and near objects. This condition also makes it difficult for patients to read. Amazingly, bifocal contact lenses are now available for those with presbyopia, making it possible for them to be free from wearing glasses, as well.
Choosing the Contact Lenses that are Right for You
With so many advancements in contact lens technology, it can be easy for a person to become confused by the multitude of choices available. Two forms of contact lenses currently available are daily wear contact lenses and extended wear contact lenses.
The wearer should take out daily wear contact lenses each night before going to bed. Extended wear contact lenses, on the other hand, can be worn overnight. In fact, they can often be worn for six or more nights in a row. Some of the newest types of contact lenses can even be worn for up to 30 nights in a row, though these are generally referred to as continuous wear contact lenses. The reason these contact lenses can be worn for such great lengths of time is because they are oxygen permeable, which is a great step in the right direction for contact lenses because it helps keep the eye healthy.