Whether you need glasses depends on how well your eyes bring things into proper focus. The cornea, or clear front window of the eye, and the lens inside the eye work together to focus light rays entering the eye. For perfect vision, light rays must come into focus precisely on the retina. The retina is a light-sensitive tissue at the back of the eye that works like the film in a camera. If the light rays don’t focus precisely on the retina, vision will be blurred or distorted. As a result, errors of refraction (nearsightedness, farsightedness, presbyopia, or astigmatism) may occur.
An ophthalmologist can easily detect these vision disorders during an eye exam and prescribe a pair of glasses or contact lenses to give you the clearest vision.
Four Types of Visual Impairments
Nearsightedness is also called myopia. With myopia you can clearly see things that are up close, but things that are far away looked blurred. A nearsighted eye focuses light rays from distant objects too far in front of the retina. Usually nearsightedness first appears in late childhood. It increases during the teenage years and levels off in early adulthood.
Normal versus Nearsighted
If you are farsighted, you can see things that are far away better than things that are up close. It’s also called hyperopia. With hyperopia, light rays are focused too far behind the retina. It is normal for young children to be slightly farsighted, often not enough to need glasses.
Normal versus Farsighted
Another type of focusing problem is astigmatism. It occurs when the cornea or lens is football shaped and vision is distorted. Astigmatism causes a distortion of vision much like a funny mirror at an amusement park. With astigmatism, a round clock might look elongated, with some of the numbers clearer than others. Astigmatism can occur alone or with myopia or hyperopia. It usually doesn’t change much over time.
Normal versus Astigmatic
Presbyopia is age related and occurs in all individuals starting in the early 40′s. The muscles inside the eye lose flexibility and one notices difficulty reading. This progresses with age and reading glasses or bifocals are the mainstay treatment. Some patients can wear bifocal or monovision contact lenses.