lasik prk lensectomy

What are the causes of focusing problems?


   Nearsightedness (Myopia)
   Farsightedness (Hyperopia)
   Astigmatism
   Presbyopia

 

Crisp vision is achieved when light rays are focused and processed by the many parts of the eye. Incoming light rays are focused on the retina by both the cornea and lens. The cornea is the transparent "window" located at the front of the eye. It is responsible for 2/3 of the "bending" of light rays. Inside the eye the lens provides the additional 1/3 of the bending of the image.

The retina, located in the back of the eye, is the portion of the eye that receives focused images and translates them into vision.

All of the eye's parts must be correctly shaped for images to be clearly focused on the retina. The eye's shape is important in determining clear vision. If the eye is either too short or too long, light rays are not focused properly on the retina. Images will also be blurry if the cornea has an uneven shape.

Nearsightedness (Myopia)

Nearsightedness (Myopia)Nearsightedness is the most common focusing problem in the United States, affecting 25-30% of our population. Nearsighted individuals can see things better up close than they can in the distance. The most common reason for nearsightedness is the eye is too long in relation to its focusing parts, or the cornea is to steep. As a result, the cornea and lens focus light rays from distant objects too quickly, and they are blurred by the time they reach the retina.

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Farsightedness (Hyperopia)

Farsightedness affects about 10% of the U.S. population. Farsightedness is a focusing problem Farsightedness (Hyperopia)usually resulting from an eye that is too small, or a cornea that is too flat. As a result, the cornea and lens cannot focus the light rays quickly enough to achieve a focused image on the retina. The effects of hyperopia vary with age because of the loss of flexibility of the natural lens. Young people may not notice any effects until their thirties, but as they begin to age, near objects begin to become blurry. Over time, farsighted individuals usually have blurry vision for both near and far objects.


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Astigmatism

Astigmatism is an inability of the eye to clearly focus images from any distance. This can occur because the shape of the cornea is not perfectly spherical. Instead of being spherical, corneas with astigmatism have a steeper curvature in one direction than another. This results in two different radii of curvatures. Corneas with pronounced astigmatism are shaped more Astigmatismlike a football (with a steeper curvature in one direction and a flatter curvature in the other) than a well-rounded basketball (with the same curvature in all directions). Most individuals have some degree of astigmatism that is usually small enough not to significantly affect the quality of vision. However, if the amount of astigmatism is greater it can cause a focusing problem. It is common to see astigmatism associated with both nearsightedness and farsightedness.

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Presbyopia

Presbyopia is a focusing problem that occurs in most people when they reach their mid-forties. In younger individuals the Presbyopianatural lens of the eye is soft and pliable. This flexibility permits the natural lens to change its shape, allowing it to focus on objects up close. However, as we age the lens loses its flexibility and can no longer focus clearly on near objects. Even people with perfect distance vision will need reading glasses when presbyopia develops. Therefore even if you achieve excellent distance vision through surgery, reading glasses are usually necessary beginning around 45 years of age. The effects of presbyopia can be masked with LASIK surgery by a procedure know as monovision. Monovision can offer both near and distance vision to a person with presbyopia, and this option should be discussed with our staff.

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