Also named as nearsightedness, myopia is so common today that it is estimated to affect one third of the population in the world. In contrast to hyperopia which deprives people from close vision, people with myopia can see close objects but can not manage distance things such as highway signs. As people age, myopia will stop progressing and become stable, although sometimes it performs myopic creep. Myopia is one of the three major visual refractive errors. The other two conditions are hyperopia and astigmatism.
The principle and consequences of myopia
Belonging to a same category of eye problems, both myopia and hyperopia involve irregular eyeball shapes. People with myopia have longer eyeballs than normal people, so that light rays are focused in front of the retina. Hyperopic patients have eyeballs with an opposite abnormality. It is well-known that normal, clear vision requires a light focus right on the retina. Without external interference, myopic people always squint to see distant objects and may suffer from headache or eye strain. What’s more, people who wear eyeglasses or contact lenses with an improper prescription are also bothered by these symptoms.
Prescription eyewear products for myopia correction
As a common vision condition in modern times, myopia is well-known and scientists have developed a couple of solutions to its correction. The most popular choice is to wear prescription eyewear including eyeglasses and contact lenses. Once a myopic patient’s eyes are precisely tested and measured, prescription lenses can be customized according to his or her vision demand and clear vision will “return”. Whether it is necessary to wear prescription eyeglasses or contact lenses full-time depends on the degree or severity of myopia. People with myopia have prescriptions with negative numbers, and a larger number represents a heavier myopia.
Available surgical treatments
Refractive surgeries are becoming popular since they can reshape the cornea of a myopic patient and eliminate the need for Rx eyewear. PRK and LASIK are two of the available refractive surgeries, both of which use an excimer laser. While PRK just removes a layer of corneal tissues and flattens the cornea, a LASIK procedure involves a flap cut through the top of the cornea. Other laser eye surgeries for vision correction include PresbyLASIK, LASEK, and Epi-LASIK etc. Each of these surgeries costs several thousand dollars per eye.
Ortho-k contact lenses and phakic intraocular lenses
For night wear, special contact lenses applying orthokeratology (ortho-k) technology can reshape the cornea overnight and provide clear vision during daytime without the help of Rx contact lenses or glasses. As implantable lenses, phakic intraocular lenses (IOLs) can deal with special situations that are beyond LASIK and PRK. These IOLs are permanently placed in the eye during a surgery, eliminating any maintenance.
Photodynamic therapy for pathologic myopia correction
There is also pathologic myopia, which is extremely severe and can not be corrected by any of the above treatments. This type of myopia occurs in children with extremely elongated eyeball by age 12. The situation will worsen as children age and unfortunately develop abnormal growth of new blood vessels. There was no effective treatment during a long period until the approval of drug Visudyne along with non-thermal laser application in 2001. This treatment named photodynamic therapy has been proved to be effective.
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