What's the difference between refractive and non-refractive errors?

• refractive errors: Refractive errors occur when the eye does not focus the light that enters the eye, resulting in blurred vision.
• non-refractive errors: Non-refractive errors are caused by eye diseases.

What causes refractive errors?

Refractive errors (myopia and hyperopia­, or "farsightedness") have been found to cluster in families. These inherited patterns may be:

• dominant (one gene was inherited from a parent with a refractive error)
• recessive (caused by two genes, one inherited from each parent, who may or may not have a refractive error)
• multifactorial (combination of genes and environment)

Refractive errors are also present in a number of genetic disorders, such as Marfan syndrome and Down syndrome.

What are the symptoms of myopia?

Myopia is usually noted in children around the ages of 9 or 10. It might be discovered if your child cannot read the blackboard from the back of the room, but can see to write and read without a problem.

Other signs and symptoms may include:

• headaches
• nausea after reading
• holding books close to his face
• writing with his head very close to the table
• sitting very close to the television
• squinting when looking at things that are far away