Ametropia

Refractive error refers to a deviation from normal visual acuity and the eyes’ ability to focus at different distances, as well as deviations in colour vision, eye motility, the coordination of the eyes, and twilight vision.

Nearsightedness / myopia: Only nearby objects are seen clearly. Objects farther away appear blurred. To see nearby things clearly, the eye does not need to strain.

Farsightedness / hypermetropia: The eye already has to strain to see objects far away clearly— and even more so for nearby objects. This is not difficult in childhood and young adulthood.

Astigmatism: If the cornea of the eye is not evenly curved in all directions—so it is not perfectly round like a ball, but rather like an egg, more curved in one direction and less curved along the perpendicular axis—this is referred to as astigmatism. The eye then, so to speak, has two different diopter strengths in the respective directions. This can be corrected with suitable glasses and contact lenses.

Presbyopia: This is not the same as farsightedness, and the commonly used term age-related farsightedness is not entirely correct. Presbyopia means that the eye can no longer adjust to different distances. A person with normal vision will still see clearly at a distance, but can no longer focus up close. Reading glasses / near-vision glasses are then needed. A nearsighted eye, which does not need to strain to see up close, will continue to see clearly at near distances. A farsighted eye, which already has to strain when looking into the distance, will then also need glasses for distance vision. Presbyopia begins from the age of 40 and gradually increases in strength.