What are refractive errors?
The following are the most common refractive errors, all of which affect vision and may require corrective lenses for correction or improvement:
Astigmatism. Astigmatism is a condition in which an abnormal curvature of the cornea can cause two focal points to fall in two different locations – making objects up close and at a distance appear blurry. Astigmatisms may cause eye strain and may be combined with nearsightedness or farsightedness. Astigmatism can start in childhood or in adulthood. Some symptoms include headache, eye strain and/or fatigue. Eye rubbing, lack of interest in school and difficulty in reading are often seen in children with astigmatism. Depending on the severity, eyeglasses or contact lenses may be required.
Hyperopia. Commonly known as farsightedness, hyperopia is the refractive error in which an image of a distant object becomes focused behind the retina, either because the eyeball axis is too short or because the refractive power of the eye is too weak. This condition makes close objects appear out of focus and may cause headaches, eye strain and/or fatigue. Squinting, eye rubbing, lack of interest in school and difficulty in reading are often seen in children with hyperopia.
Myopia. Commonly known as nearsightedness, myopia (the opposite of hyperopia) is a condition in which an image of a distant object becomes focused in front the retina, either because the eyeball axis is too long or because the refractive power of the eye is too strong. Myopia is the most common refractive error requiring correction seen in children. This condition makes distant objects appear out of focus and may cause headaches and/or eye strain.
Eyeglasses or contact lenses may help to correct or improve myopia by adjusting the focusing power to the retina.