SOME COMMON AND TRIFLE EYE DISEASES

Nowadays, we can always easily get some popular and slight optical problems for example short-sighted or long-sighted which are actually eye diseases. They are becoming more and more common among the busy city inhabitants. Below, I will introduce three common eye diseases which I think everyone must know. They are myopia, astigmatism and presbyopia.

MYOPIA, HYPEROPIA AND ASTIGMATISM

When you first look at these words myopia, hyperopia and astigmatism, you may perhaps presume that they must be some very rare or serious kind of eye diseases. But as a matter of fact, myopia, hyperopia and astigmatism are three very common eye diseases which you can find everywhere nowadays, or you may have these diseases already even. Myopia is the medical term of nearsightedness and hyperopia is the medical term of farsightedness.

What is Myopia?

Myopia (nearsightedness) occurs when the eyeball is too long for the cornea's curvature. The rays of light entering the eye do not come to a sharp focus on the retina at the back of the eye. Instead, they focus further forward in front of the retina, producing a blurred image. That explains why the myopic patients find the objects further In the distance blurry. However, they can see clearly the near objects without using glasses because the light rays from a short distance can just focus on the retina and thus the close objects are sharply in focus.

What is Hyperopia?

Hyperopia, also known as farsightedness. It occurs when the eyeball is too short and/or the surface of the cornea is too flat so the light rays cannot be just converged to the retina. Instead, light rays entering the eye focus behind the retina, and as a result, a blurred image is produced. Farsighted patient, however, can use their freeing muscle to pull the image forward onto the retina and they can see the near objects much clearer.

What is Astigmatism?

Actually, many patients with myopia have some degree of astigmatism. In the astigmatic eye, the front of the cornea is not equally curved but is slightly oval in shape. As a result, the rays of light that enter the eye are bent unequally and cause distortion or tilting of the image. Patients with high degree of astigmatism have blurred vision not only for distant objects as with myopia, but for near objects as well.

How can Myopia be corrected?

The majority of the people who have got Myopia, hyperopia and astigmatism would unhesitatingly go to a optical shop and prescript a pair of glasses or the new contact lens in order to compensate for them. There are of course, varying degrees of myopia, hyperopia and astigmatism. The more any one of them we get, the more blurred objects appear, the higher the eyeglass prescription and the thicker our glasses.

But as the science and technology in optics is more and more advanced today, we can now not only compensate for myopia, hyperopia and astigmatism, instead we can able to correct them by not wearing glasses or contact lens but by photorefractive keratectomy (PRK), a laser vision correction method for mainly myopia. It uses computerized excimer laser technology to improve vision and eliminate or reduce the need for glasses or contact lens.

The excimer laser delivers a cool, gentle beam of ultraviolet light in pulses that last a few billionths of a second. Each pulse instantly evaporates a microscopic amount of corneal tissue - less than the thickness of a human hair. So, it is a very accurate and at the same time painless procedure which takes only 15 to 45 seconds. But what is more amazing is that the treatment does not weaken the cornea and the patient only needs 24 to 48 hours of recovery period. Most patients return to normal activity in 2 days and usually notice much improved vision 3 to 5 days following treatment. Lastly, the treatment is permanent.

PRESBYOPIA

What is Presbyopia?

Presbyopia is the normal process of aging, which occurs when we are 40 to 50 when the focusing system is not strong enough to allow one to comfortably see at close distance. As everyone experience presbyopia sooner or later, the nearsighted people began to use bifocals in their forties, and those who never need glasses before may require reading glasses. So, one advantage to mild myopia is the ability to remove their glasses after 40 or 50 because their myopia effectively counteracts presbyopia. Anyone who gets presbyopia must wear glasses for it is not affected by laser treatment.