Why Eye Problems Begin

If you’re reading this, chances are you've already been dealing with contact lenses or eye glasses, or both, for years and know all too well the hassles and limitations that come with each. Here’s essentially what’s happening.

As light rays pass through one medium to another, such as from air to water, they bend.1 This is known as refraction. When these rays pass through the eye tissues of the cornea  Cornea: The clear, curved surface at the front of the eye through which light enters the eye. Along with the sclera, the cornea provides external protection for the eye.   and lens, they are also refracted in a manner that brings them into focus on the retina. When the eye is unable to focus light on the retina, usually because the shape of the eye isn’t quite right, this is called a refractive error.  Refractive error: Vision problem caused by an imperfect optical system, most commonly myopia, hyperopia, and astigmatism.  

Below is a brief overview of the most typical refractive error conditions, as well as eye problems that stem more from aging and the stiffening or clouding of the eye’s lens that can develop in our later years.

Click on Each Condition Name for More Information


Also called myopia,  Myopia: A refractive error resulting in the inability for the eye to see distant objects. Also referred to as "nearsightedness." Occurs when the eyeball is too long or when the cornea has too much curvature, preventing the light entering the eye from focusing correctly on the retina and resulting in blurry vision at a distance. Eyeglasses, contact lenses, and refractive surgery are treatment options for correcting vision impairment caused by myopia.   nearsightedness (blurred distance vision) is the most common refractive error. This happens typically when the eye is too long or the cornea too steep. This extra length causes light from distant objects to focus at a point just short of reaching the retina, which causes the light to disperse and provides the brain with an out-of-focus image.

Eye Problems


The common term for hyperopia,   Hyperopia: The medical term for "farsightedness," a refractive error resulting in an inability to see objects at close range. Typically caused by either a cornea with too little curvature or an eyeball that is too short, hyperopia causes light entering the eye to focus improperly on the retina, resulting in blurry close-up vision. Eyeglasses, contact lenses, and refractive surgery are treatment options for correcting vision impairment caused by hyperopia.   farsightedness (meaning you can’t see things up close) is caused by an eye that is too short or a cornea that is too flat. The reduced length leaves the cornea and lens   Lens: The transparent disc behind the pupil that brings light into focus on the retina.   insufficient space to bring together the light rays to a focal point upon the retina, thus focusing the image beyond the retina and, again, sending poor signals to the brain.

A Farsighted or Hyperopic Eye


Another term used for poor eye curvature, astigmatism is what happens when the cornea is not round enough but shaped more like a football, which prevents the eye from being able to focus clearly at any distance, near or far.

An Astigmatic Eye


This condition typically begins to affect people between the ages of 40 and 50. Presbyopia occurs when the natural lens of the eye ages, thus hardening and losing its flexibility, which typically results in loss of up-close vision and often leads to a need for reading glasses.


Contrary to popular belief, a cataract is not a film that forms over the eye2 but rather a change in the clarity of the lens inside your eye, allowing less light to pass through. This gradual clouding can make vision less sharp over time. The light that does make it through to the retina is diffused, turning vision blurry.

Vision problems are traditionally corrected with eyeglasses or contact lenses, but today you have more options. Explore them. Read more about the LASIK procedure here.

Next: Eye Exams



  1. Oracle ThinkQuest Education Foundation. Light Rays, Refraction. http://library.thinkquest.org/27066/lightrays/nlrefraction.html.  Accessed on October 16, 2010.
  2. Oregon Academy of Ophthalmology. Public Info: Cataract.
    http://www.oregoneyephysicians.org/pages/medinfo-pages/cataract.html.  Accessed October 16, 2010.