The most frequent anomaly is myopia or shortsightedness, causing a diminished visual acuity for distance.

Hyperopia or farsightedness, causing a diminished acuity for near, is frequent in older people and increases with age.

Astigmatism : Irregular or uneven curvature of the anterior corneal surface of the eye, necessitates a spectacle correction. When important anomalies are present headache or decreased vision may result. The major part of these refractive anomalies can be treated with laser (Excimer - Lasik - Holmium) or with surgery.

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