Crushing (Refraction) Defects

The eye is an optical system similar to a camera. Light and images coming from the outside are refracted in the cornea (the outermost transparent layer of the eye) and the lens layer and reach the visual point on the retina. In a normal eye, the rays coming from the outside are refracted in the cornea and lens and fall into the visual center, forming a clear image. In some cases, depending on the cornea, lens and eye structure, images may not be clearly formed on the retina.

Myopia

It develops as a result of focusing the rays coming from outside before they reach the point of view. It occurs due to the long anteroposterior axis of the eye or when the refraction of the cornea and lens changes. Since the adaptation power is very low in myopic eyes, the person has to use glasses to see far.

Astigmatism

It occurs when the refractive power of the cornea is different in two perpendicular axes, as a result of which the image is refracted in different planes. It may vary depending on the structure of the cornea and lens. Astigmatism causes reflection and blurred vision at all distances. Astigmatic vision can be compared to the image formed by crooked mirrors in circuses.

Hypermetropia

It develops as a result of focusing the rays coming from outside behind the visual point. It occurs due to the short anterior-posterior axis of the eye or when the refraction of the cornea and lens changes. The power of adaptation in hypermetropic eyes is high. People with low degree of hyperopia can see normally by adapting, but the eyes get tired quickly. In high hyperopia, both distance and near vision are impaired.

Presbyopia (Age-Related Near Vision Disorder)

It is the loss of flexibility of the lens due to aging and as a result, the deterioration of near vision. It begins at the age of 35-40 and progresses continuously until the age of 60.

Keratoconus

It is the thinning of a part of the corneal surface and protruding forward. These people cannot see clearly with glasses. They can use contact lenses specially produced according to the degree of the disease. In very advanced degrees, corneal transplant surgery called keratoplasty may be required.

Myopia, hyperopia, astigmatism and presbyopia are general refractive errors of the eye. While these refractive errors may occur in the eye individually, more than one refractive error may occur together. The refractive error can occur in one eye or both. Apart from these, special refractive errors may occur due to defects of the cornea and lens. In one eye, along with a refractive error, there may be defects in the cornea, the visual layer of the lens, or the optic nerve. Therefore, people with refractive errors should undergo regular eye and fundus examination every year. If there is any suspicion of eye shift or visual impairment in children, eye control should be performed as soon as possible. Even if there is no problem, eye examinations should be done around the age of 4 years.

There are many alternatives for people with refractive errors to see clearly.

• They can use glasses.
• They can use contact lenses.
• They can get rid of all or some of the refractive errors with excimer laser treatment.