Refractive errors in children (short sight, long sight, astigmatism)

Refractive errors are commonly encountered in children. They cause eye strain, lack of interest in studies, squint and even visual impairment.

Hence every child should have an eye check up before entering school. In order to understand these errors it is essential to have some knowledge of normal vision.

For more information about the structure and function of eyes visit healthy eyes.

The eye is somewhat like a camera. If an object has to be seen clearly it has to form an image on the retina (the innermost layer of the eye which has receptor cells for creating the image of an object and transmitting it in the form of electrical impulses to the brain).

The eye also has a lens. This lens is unique. It can change its shape to some extent. When we look at an object which is near the lens becomes a little more rounded, so that the light rays converge on the retina for a clear image. When we look at a far away object the lens flattens a bit.

Short sight (myopia): In this condition nearby objects are seen clearly but objects for away are blurred. This is because light rays from distant objects are brought to focus in front of the retina instead of on the retina. This defect can be corrected using concave lenses which cause some divergence of light rays so that they focus on the retina.

Far sight (long sight, hyperopia): In this condition a person can see distant objects well but objects which are near are blurred. This is because light rays from nearby objects are brought to focus behind the retina. The condition can be corrected by using convex lenses which increase the converging capacity of the eye.

Astigmatism: In astigmatism the rays from an object are focused in two different planes. Hence the image will not be clear. Both the planes can be in front of the retina or behind the retina. It is also possible for one plane of focus to be in front of retina and the other behind the retina.

Older children above 15 years may wear contact lens if they do not like to wear glasses. Lasik refractive surgery may be performed after 19 years.

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