The most common vision problems are refractive errors, more commonly known as nearsightedness, farsightedness, astigmatism and presbyopia. Refractive errors occur when the shape of the eye prevents light from focusing directly on the retina. The length of the eyeball (either longer or shorter), changes in the shape of the cornea, or aging of the lens can cause refractive errors. Most people have one or more of these conditions.
WHAT IS REFRACTION?
Refraction is the bending of light as it passes through one object to another. Vision occurs when light rays are bent (refracted) as they pass through the cornea and the lens. The light is then focused on the retina. The retina converts the light-rays into messages that are sent through the optic nerve to the brain. The brain interprets these messages into the images we see.
WHAT ARE THE DIFFERENT TYPES OF REFRACTIVE ERRORS?
The most common types of refractive errors are nearsightedness, farsightedness, astigmatism and presbyopia.
Nearsightedness (also called myopia) is a condition where objects up close appear clearly, while objects far away appear blurry. With nearsightedness, light comes to focus in front of the retina instead of on the retina.
Farsightedness (also called hyperopia) is a common type of refractive error where distant objects may be seen more clearly than objects that are near. However, people experience farsightedness differently. Some people may not notice any problems with their vision, especially when they are young. For people with significant farsightedness, vision can be blurry for objects at any distance, near or far.
Astigmatism is a condition in which the eye does not focus light evenly onto the retina, the light-sensitive tissue at the back of the eye. This can cause images to appear blurry and stretched out.
Presbyopia is an age-related condition in which the ability to focus up close becomes more difficult. As the eye ages, the lens can no longer change shape enough to allow the eye to focus close objects clearly.