Refractive Errors - myopia, hyperopia, presbyopia, and astigmatism
Refractive errors include myopia, hyperopia, presbyopia, and astigmatism, eye conditions that are very common. Most people have one or more of them. Refractive errors can usually be corrected with eyeglasses or contact lenses.
If you have myopia you can clearly see close objects, but distant objects are blurry. Myopia is usually caused by the eyeball being too long. Myopia occurs in different degrees from minimal to extreme. The more myopic you are the blurrier your vision is at a distance and objects will have to be closer to you so you can see them clearly.
If you have hyperopia, you can see distant objects more clearly than close ones, but depending on you age, all objects might be blurry without glasses. Hyperopia occurs when the eyeball is too short for the light rays to focus clearly on the retina.
If you have astigmatism, your cornea is not perfectly round; rather it is more oval, and so it is not able to focus light as clearly as a round cornea. Astigmatism rarely occurs alone; it usually accompanies myopia or hyperopia.
If you have presbyopia, you have the lost the ability to focus up close as a result of too many birthdays. Most people are between 40 and 50 years when they realize for the first time that they can’t read objects close to them. The letters of the phonebook are “too small” or they have to hold the newspaper farther away from their eyes to see it clearly.
Ortho-K, also known as Corneal Refractive Therapy (CRT), is corneal reshaping through overnight use of specialty hard, gas-permeable lenses to temporarily reduce myopia. Hence, it allows users to be independent of glasses or contact lenses throughout the daytime.
CRT is for those
who have mild to moderate myopia and would like not to wear glasses or contact lenses during the daytime.
who want to reduce myopia progression. Clinical studies have shown that children wearing CRT lenses have 40% less myopia progression than untreated controls.
After the first night of wearing CRT lenses, most patients will able to achieve independent, uncorrected vision throughout the next day. Follow up visits after a week, two weeks and a month of initial wear are required to obtain optimal fit of the lenses. CRT is a generally safe procedure when used properly. The treatment has been FDA-approved since 2002. Since it involves overnight contact lens wear, there is a small risk of corneal infection, and thus, close monitoring of corneal health is required. Regular visits every 3-4 months are necessary to monitor corneal health.