The following is a list of the most common refractive errors, all of which affect vision and may require corrective lenses for correction or improvement.
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, eyestrain and/or fatigue. Eye rubbing, lack of interest in school and difficulty in reading are often seen in children with astigmatism. Depending upon the severity, eyeglasses or contact lenses may be required.
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. This condition is uncommon in children.
Eyeglasses or contact lenses may help to correct or improve hyperopia by adjusting the focusing power to the retina.
Commonly known as nearsightedness, myopia is a condition in which, opposite of hyperopia, 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 seen in children. This condition makes distant objects appear out of focus and may cause headaches and/or eyestrain. You may notice that your child is holding books too close to his/her face and writing with his/her head very close to the table.
Eyeglasses or contact lenses may help to correct or improve myopia by adjusting the focusing power to the retina.
What Causes Refractive Errors?
Refractive errors (myopia and hyperopia) have been found to cluster in families. A variety of inheritance patterns have been observed including dominant (one gene passed from a parent with a refractive error to a child), recessive (caused by two genes, one inherited from each parent who may/may not have a refractive error), and multifactorial (combination of genes and environment). Refractive errors are present in a number of genetic disorders, such as Marfan syndrome and Down syndrome.