Flinthills Eyecare: Refractive Visual Problems


Doctors
Office Information
	Payment and Insurance Options
	Privacy Policy
Vision Correction
	Contact Lenses
		Lens Types
		Lens Care
	Eye Glasses
	Refractive Eye Care
		Refractive Surgery
Vision Therapy
	Developmental Evaluation
Children's Vision
	SEE TO LEARN
Eye Disorders
Informational Links

Refractive Visual Problems

The primary function of your eye is to focus light. Your eye works like a camera. The cornea, the front lens of your eye, provides most of the focusing power. The lens, inside your eye, provides the fine tuning or focusing needed for reading ability. The retina at the back of the eye acts like the film in a camera. For you to see clearly, light rays must focus precisely on the retina. You need glasses or contact lenses when your eye cannot properly direct light rays to focus on the retina. People who wear corrective lenses might have one of the following refractive problems.
Refractive Visual Problems
Myopia, hyperopia, and astigmatism are considered "refractive" errors that require corrective lenses to properly bend (or refract) light rays entering the eye. It is the proper refraction of light onto the retina that achieves "normal" eyesight.
Myopia		Hyperopia
Myopia (Nearsightedness) means that near objects are clearer than distance objects. This occurs when your eye is too long in relation to the curvature of your cornea. Light rays entering the eye come to a focus in front of the retina, which produces a blurred image.		Hyperopia (Farsightedness) means that distance objects are clearer than near objects. This occurs when your eye is too short in relation to the curvature of your cornea. Light rays entering the eye come to a focus behind the retina and this also will cause a blurred image.
Astigmatism
Astigmatism occurs when your cornea is oval and not round in shape. Usually the cornea is shaped more like a baseball but when there is astigmatism the cornea is shaped more like a football. The result is unequal bending of light rays entering the eye. This produces two different focus points causing distortion.

Measuring Refractive Visual Problems
Refractive visual problems are measured in units called diopters. The more nearsighted or farsighted you are the highter your prescription is in diopters.
	Mild Myopia and Hyperopia	Less than 3.00 Diopters
	Moderate Myopia and Hyperopia	3.10 to 6.00 Diopters
	Severe Myopia and Hyperopia	6.10 to 9.00 Diopters
	Extreme Myopia and Hyperopia	More than 9.10 Diopters

	Mild Astigmatism	Less than 1.0 Diopters
	Moderate Astigmatism	1.10 to 2.00 Diopters
	Severe Astigmatism	2.10 to 3.00 Diopters
	Extreme Astigmatism	More than 3.10 Diopters

How to read your prescription.
Your prescription is written in three numbers, which will tell you which category you fall into. Example: -4.00 -1.50 X 180 The first number (-4.00) identifies how much nearsightedness or farsightedness you have. The sign identifies whether you are nearsighted (-sign) or farsighted (+sign). The second number (-1.50) identifies how much astigmatism you have. This number can be written with either a (+) or a (-) sign. The third number (180) is the axis, which indicates the location of your astigmatism. An axis of 180 degrees means the astigmatism is horizontal. Therefore, -4.00 -1.50 X 180 means that the patient is moderately nearsighted, with a moderate amount of astigmatism in a horizontal direction.

Refractive Surgery
If glasses and contact lenses seem too restrictive for your lifestyle, consider refractive surgery. There are several procedures available to correct refractive errors (the reason for glasses) and depending upon your visual goal this may be the best option. We have spent many hours in education and have traveled throughout the United States and Canada to learn about these procedures. Many of our patients have undergone refractive surgery and are doing great. Click here for more information concerning refractive surgery.