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What are the 5 Types of Refractive Errors?

Last updated 7 years ago

The eyes are some of the most complex and most important organs in our body.  The cornea is a piece of the eye that is crucial to its proper functioning, and when it’s misshapen in any way, it cannot properly perform its duty of refracting light for the retina.  The following five conditions are refractive errors that can result from corneal deformation.

 1.  Myopia

Nearsightedness or myopia, occurs when light entering the eye focuses in front of the retina instead of directly on it.  This is caused by a cornea that is steeper, or an eye that is longer, than a normal eye.  Nearsighted people typically see well up close, but have difficulty seeing far away.

 2.  Hyperopia

Farsightedness or hyperopia, occurs when light entering the eye focuses behind the retina, instead of directly on it.  This is caused by a cornea that is flatter, or an eye that is shorter, than a normal eye.  Farsighted people usually have trouble seeing up close, but may also have difficulty seeing far away as well.

 3.  Astigmatism

Nearly everyone suffers from astigmatism to at least some degree. 

Astigmatism means that the cornea is oval like a football instead of spherical like a basketball.  Most astigmatic corneas have two curves – a steeper curve and a flatter curve.  This causes light to focus on more than one point in the eye, resulting in blurred vision at distance or near.  Astigmatism often occurs along with nearsightedness or farsightedness.

 4.  Presbyopia

Unlike the previous conditions, presbyopia and cataracts (explained below) are both developed with age.  Presbyopia, which is literally translated to “age of sight,” is the loss of the eye’s ability to adjust focus for different distances.  This condition is often confused with hyperopia and many are not aware that this condition can not be fixed by LASIK eye surgery.  Presbyopia is not a condition of the cornea, it is the natural hardening of the internal lens of the eye (crystalline lens).  As we age, the lens becomes thicker and harder and fails to accommodate.  Monovision LASIK may be a temporary solution, but in the long term, everyone over the age of 40 gradually loses their ability to focus on objects near and arms length.

 5.  Cataracts

A cataract is characterized by the clouding of the eye’s crystalline lens.  The cloudiness gradually becomes more opaque and, if left untreated, can leave someone permanently and completely blind.  Cataracts  progress at different rates.

While LASIK surgery can correct many cases of myopia, hyperopia and astigmatism, presbyopia and cataract procedures require additional types of treatment.  To find out more about LASIK, customized LASIK, blade-free LASIK and the revolutionary implantable contact lens, the Visian ICL, contact Clear Advantage.  Call us at (603) 379–6817 or visit our website for more information.



The materials available at this website are for informational purposes only and not for the purpose of providing medical advice. You should contact your doctor to obtain advice with respect to any particular medical issue or problem. Use and access to this website or any of the links contained within the site do not create a doctor-client relationship. The opinions expressed at or through this site are the opinions of the individual author and may not reflect the opinions of the medical office or any individual doctor or physician.


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