In a normal eye; light passes through the cornea, and then through the lens and focuses at the retina located in the posterior part of the eye. If the eye cannot refract the light properly the vision gets blurred. The situation which parallel photons coming to the eye are gathered together on the retina is called emmetropia. Emmetropia is the situation which there is no refractive error.

 

There are four types of refractive errors:

Myopia: The photons coming to the eye are gathered together in the anterior part of the retina. The patients who has myopia can see nearby objects clearly, but it gets blurred when it gets far away. Myopia comes out as a result of increased anterior – posterior diameter of the eye. This is a structural problem and genetic inclination is common. It is called mild myopia if the degree is up to the 6 and severe myopia if it exceeds this degree. It is recognized between ages 8 – 14 in the childhood period.

 

Hypermetropia: The photons coming to the eye are gathered together in the posterior part of the retina. The patients who has hypermetropia have difficulties to see nearby objects. If the degree of the hypermetropia exceeds a threshold point the patients will have difficulty in seeing distant objects either. Hypermetropia comes out as a result of decreased anterior – posterior diameter of the eye. Structural and inherited features are the most common causes of hypermetropia.

 

Astigmatism: This is a situation caused by different refractions of the photons coming to the eye and as a result the photons cannot be focused at a defined point.   These patients have problems both in seeing the nearby and distant objects. Astigmatism can be seen with myopia and hypermetropia.

 

Presbyopia: The lens located in the eye can have the ability to focus easily to the objects located nearby or distant in the younger age group. But after 40 years of age the lens gets stiffer and the fixing ligaments of the lens lose their elasticity. As a result, to see the nearby objects and reading gets harder. This situation is called presbyopia.

 

Before starting the ophthalmological examination, the eyes are checked with autorefractometer. The measurement is repeated a couple of times for both eyes and if it is necessary the mean degrees are calculated. In children the measurement is done by distantly located machines specially designed for children and degrees are calculated based on measurements done on dilated pupil – eyes.

 

Refractive Error Correction:

The refractive errors in children are treated with eye-glasses. The rims are very important that must be suitable for all age groups. If the child is not feeling comfortable with the rims than he/she may refuse the treatment. In the infant age group; elastic and soft rims must be used. In the pre-school kids rims which are rounded and restrict vision from upper and lower parts of the glasses are preferred. After puberty (mean 13 – 14 years old) contact lens usage can be induced. After the age of 18 if the structure of the eye is suitable laser surgery can be suggested.