What are Refractive Errors?

For our eyes to be able to see, light rays must be bent or “refracted” so they can focus on the retina, the nerve layer that lines the back of the eye. The cornea and the lens refract light rays. The retina receives the picture formed by these light rays and sends the image to the brain through the optic nerve. A refractive error means that the shape of our eye doesn’t refract the light properly, so that the image you see is blurred. In a normal eye, the cornea and lens focus light rays on the retina.

 

Normal Eye Vision:

Myopia (Nearsightedness)

A myopia eye is longer than normal, so that the light rays focus in front of the retina. Close objects look clear but distant objects appear blurred. In myopia, distant objects are blurry because the eye is too long, and images focus in front of the retina instead if on it. Myopia is inherited and is often discovered in children when they are eight to twelve years old. During the teenage years, when the body grows rapidly, myopia gets worse. Between the ages of 20 and 40, there is usually little change.

 

Myopic Eye Vision:

Hyperopia (Farsightedness)

A hyperopia eye is shorter than normal. Light from close objects, such as the page of a book, cannot focus clearly on the retina. In hyperopia, the eye is too short for images to focus on the retina, so close object are blurry.

 

Hypermetropic Eye Vision:

Astigmatism (Distorted Vision)

The cornea is the clear front window of the eye. A normal cornea is round and smooth, like a basketball. When you have astigmatism, the cornea curves more in one direction than in other, like a football. Astigmatism distorts or blurs vision for both near and far objects. It’s almost like looking into a funhouse mirror in which you appear too all, too wide or too thin. You can have astigmatism in combination with myopia or hyperopia.

 

Astigmatic Eye Vision: