Visual or Refractive Conditions

 

Emmetropia


Emmetropia is the term used to describe an eye that requires no correction to allow for sharp, clear vision at all distances.  As light passes into the eye, it is directed into one sharp point of light that falls on an area of saturated visual receptors on the back of the eye called the fovea or macula.  The lens of the eye bends to help focus the eye on objects that are near and relaxes to focus on things far away allowing for good vision at a large range of distances.

 

 

 

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Far-sightedness or Hyperopia


This is a condition in which patients have difficulty focusing on objects that are near.  This condition is often confused with presbyopia.  As light passes into an eye with hyperopia, the light is focused into one sharp point that falls behind the fovea or macula on the retina.  However, due to the focusing ability of the eye, some patients can still achieve good distance vision by straining his or her eyes to see.  Although distance vision may be unaffected, reading and computer work suffer because there is not enough focusing ability left to see clearly at near. Eyestrain caused by this excessive focusing may cause headaches or double vision.  Glasses or contact lenses are prescribed to allow for comfortable, relaxed distance vision so that the focusing needed for near is within the normal range.

 

 

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Presybopia


This is the condition in which a patient loses the ability to focus on near objects around the age of 40.  Presbyopia occurs because the lens in the eye becomes less flexible as the aging process progresses.  This loss of flexibility results in an inability of the lens to change the point of focus from a distance object to a near object.  As a result, reading or bifocal glasses are prescribed to focus the light onto the macula or fovea while viewing a near object.


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Near-sightedness or Myopia


This is the condition in which a patient can see objects at near better than objects that are farther away.  As light passes into the eye, it is focused into one sharp point that falls in front of the fovea or macula of the retina.  Therefore, when the light reaches the fovea where the visual receptors are located, the light is a blurred area instead of a sharp image. This is why myopic patients see blurry images at a distance.  To correct this issue, a minus power lens is placed on or in front of the eye refocusing the light to the fovea resulting in clear vision for our patients.

 

 

 

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Astigmatism


This is a condition in which a patient often struggles with sharp vision at both distance and near.  As light passes into the eye, the light is not focused to one sharp point on the back of the eye.  Instead, the light is focused to an area of points called a blur circle.  The larger the size of the blur circle, the wider the range of points the light is focused to.  As this blur circle increases in size, the amount of astigmatism a patient has and needs corrected is increased.  Astigmatism is corrected by placing a lens on or in front of the eye that refocuses light to a single point on the fovea or macula providing clear vision.