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More than 70 million people in North America are nearsighted. Myopia is the medical term for nearsightedness. Myopia occurs when an eye is too long for the cornea's curvature. Light rays entering the eye do not come to a sharp focus on the retina at the back of the eye. Instead, they focus further forward, producing a blurred image. This is demonstrated in the diagram below.
The term 'nearsighted' means that you can see 'near' objects clearly without your glasses, but objects further in the distance are blurry. There are varying degrees of myopia or nearsightedness. The more myopic you are, the more blurred objects appear in the distance, the higher your eyeglass prescription and the thicker your glasses.
Of all myopic people, about 90% have corrections less than -6.00 diopters. The table below shows the categories of severity for myopia:
- Mild Myopia <-3.00 diopters
- Moderate Myopia -3.00 to -6.00 diopters
- Severe Myopia -6.00 to -9.00 diopters
- Extreme Myopia >-9.00 diopters
Almost everyone feels that their myopia is severe, because of how dramatically dependent they are on glasses and contact lenses. However, only one in ten myopic people are actually in the severe and extreme categories.
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