Refraction defects are caused by the inability of beams coming in parallel to the eye from a distant object to focus on the retina and are defined as myopia, hyperopia, and astigmatism.

In patients with myopia, beams coming in parallel with the eye gather in front of the retina, so distant objects are blurred.

Figure 1

In patients with hyperopia, beams coming in parallel with the eye gather behind the retina, so patients first complain about seeing blurred close objects, but patients with high hyperopia also see blurred distant objects.

Patients with astigmatism complain about blurred vision due to the inability of beams coming in parallel with the eye to create a single point of focus resulting from differences in refractivity of the cornea or lens in every angle. These patients may experience headaches and a feeling of heaviness in the eye when they are busy with work requiring close attention (reading books, looking at a computer screen, watching television, etc.).

Figure 2. Emmetropia and refractive errors of eye.

Refraction defects are found in the front and back distance due to deviations in the curvature of the cornea or lens from the normal. The most important risk factor is genetic inheritance.

Values are found in autorefractometric or skiascopic examinations, and refraction defects of patients are rectified with the appropriate lenses by determining visual sharpness of patients from certain distances.

Refraction defects are rectified via glasses or contact lenses, depending on the preference of the patient and suitability to the visual examination. Refraction defects can also be rectified through different surgical methods by applying laser onto the corneal surfaces.