REFRACTIVE ERRORS

Refractive error occurs when light is not properly focused on the retina, due to the shape of the eye. The three types of refractive error are Myopia (near-sightedness), Hyperopia (far-sightedness), and Astigmatism.

Myopia

Myopia occurs when light coming into the eye focuses in front of the retina, rather than directly on it. This results in distance vision blur. The retina is the neural lining of the back of the eye, and acts like the film of a camera. If light does not focus directly onto the retina, the image will appear blurry. In axial myopia, the eye is longer than normal. In curvature myopia, the cornea or lens of the eye may be steeper than normal. A proper lens placed in front of the eye can refocus the image from in front of the retina to directly on it, thus making the vision clear. This is typically done with glasses or contact lenses. Reshaping the cornea to flatten it using laser surgery (Lasik) can also be effective, but this is not approved for children. Myopia is mostly genetically determined, although environmental factors, such as the amount of near work done, can also play a role.

 

Hyperopia

Hyperopia occurs when light coming into the eye focuses behind the retina, rather than directly on it. This results in near vision blur. In cases of high hyperopia, distance objects will appear blurry as well. In axial hyperopia, the eye is shorter than normal. In curvature hyperopia, the cornea or lens of the eye may be flatter than normal. A proper lens placed in front of the eye can refocus the image from behind the retina to directly on it, thus making the vision clear. This is typically done with glasses or contact lenses. Reshaping the cornea with laser surgery (Lasik) can also be effective, but this is not approved for children. A small amount of hyperopia is normal in children. However, higher levels of hyperopia can lead to blurred vision, headaches when reading, amblyopia (lazy eye) and strabismus (crossed eyes).

 

Astigmatism

Astigmatism occurs when light is focused unevenly on the retina. This occurs because the cornea or the lens of the eye has an irregular curvature, more like that of a football, rather than a baseball. Very small amounts of astigmatism are not uncommon, and often these patients do not require glasses. Those with higher amounts of astigmatism have blurred or distorted vision at all distances, but especially far away. Just like with myopia and hyperopia, a proper lens placed in front of the eye can even out the retinal image and make the vision clear. This is usually done with glasses or toric contact lenses. Reshaping the cornea with laser surgery (Lasik) can also be effective, but this is not approved for children.

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