Myopia (Nearsightedness) | Defined
What is Myopia?
Myopia, also known as nearsightedness or shortsightedness is a common eye refractive error in which people are able to see close by objects clearly but find difficulty to see farther objects. In general, a myopic eye can clearly read a book but cannot see television screen, or a white board in school clearly.
Myopia affects nearly 30% of the US population. However till date the exact cause for myopia is unknown, but it is evident that the risk of being affected increases if any or both of the parents are myopic.
Understanding what happens in case of myopia
In case of a normal eye, when we see an object the light rays gets reflected from the object and enters eye lens through cornea. The eye lens bends the coming light rays and focus it on the retina.
But in case of a myopic eye, either the eyeball is too long or the cornea is too curved. This causes light rays to focus at a point in front of the retina. Which is why the image formation takes place in front of retina and not on it causing a blurry image.
A myopic eye cannot focus on a farther object clearly. This is the only reason why it is commonly called nearsightedness or shortsightedness.
If you are getting difficulty in seeing road signs, movie screen or a television screen but can read well enough your books, then you may be affected by nearsightedness.
Other symptoms may include head aches and eye strain. Extreme myopia increases the risk of retinal detachment, Cataract, or Glaucoma.
How is Myopia diagnosed?
Nearsightedness can be diagnosed by an eye care professional with an eye examination. This is usually initiated by a visual acuity test. In this test a visual standardized charts or cards with rows of letters that decreases in size from top to bottom are shown. You will be asked to cover one eye and read the texts on the board. The test will then be followed by your other eye closed with the same procedure. If you find difficulty in reading, then your doctor will use Retinoscope to check your retina and determine the amount of refractive error you have.
What are the treatments available ?
There are several options available to rectify your myopic eye and to regain the clear distant vision. These methods help in image formation onto the retina instead of forming in front of it. They include :
- Eyeglasses are one of the most common way to treat myopia. They are much safe and adjustable. It is prescribed if your eye power continues to deteriorate. Once the eyes stopped growing there are several options available.
- Contact lens also acts like eyeglasses. They are less safe compared to eyeglasses as they might create infection in the eye.
- Ortho K or CRT (Corneal Refractive Therapy) is another option available. It is a non surgical procedure in which you wear a rigid specifically designed series of contact lens to gradually reshape the curvature of cornea. The lens places pressure on the cornea to flatten it. This changes how light entering the eye is focused and thereby may temporarily correct the vision in mild myopia. It is to wear for a limited time like overnight.
- Lasik Surgery is a surgical procedure for correcting your myopic eye. In this central part of the outer corneal surface is lifted and folded back to expose the inner tissue. Then laser is used to remove some corneal tissue needed to reshape your eye. The outer tissue is then placed back to the position.
- PRK is another such surgical procedure available. In this laser is used to remove desired amount of corneal tissue to reshape the eye.
- Vision Therapy is also claimed to reduce myopia extent. But there is no clear evidence of it that it works. Various eye exercises and relaxation therapies are used to get rid of nearsightedness. Bates method is the most advisable and prominent one.