Common Knowledge of Refractive Vision Problems - By: AdamDouglas

Eye is one of the most precious gifts the God endows us with. It enable us the ability to observe the world. However, since eye is such a familiar part in our body, have you ever thought how this magic organ works?

If compared vividly, eye works as a camera does and it is composed of several main parts, including pupil, cornea, crystalline lens, ciliary muscles, retina and optic nerve.

Vision begins when light rays are reflected off an object and enter the eyes through the cornea, the transparent outer covering of the eye, and then through the lens. When the image reaches the retina, the sensory cells which we refer as rods and cones in it change the image to electrical energy which is passed to the tiny optic nerve fibers in the retina. During this process the image data is delivered to the brain to start the interpretation.

The reason why people compare the work of the eye to that of a camera is that the cornea acts as the a lens in a camera which bends light as it enters the eye or refracts the light further.

If your eyesight is 20/20 perfect vision, their combined light refraction focuses the light rays on the retina. The angle of light coming from a distant object is smaller than that coming from a close-by object. Thus we can see when one who suffers from nearsighted, it is needed to change the angle of the light of object reflect into the eyes, therefore a surgery to correct vision is usually to reshape cornea.

The vast majority of vision problem result from imperfect formation of the eye's refractive system. Refractive errors include four types as follows:

Myopia. Myopia or say nearsightedness is by far the most common vision problem. Nearsighted people have difficulty seeing far away objects clearly but have no problem to see things closely, because when the light comes to the retina, it has diverged. There are two ways in which myopia can occur: the eyeball is too long; the lens/cornea optical system of the eye is too strong.

Hyperopia. Hyperopia or say farsightedness is the second most common vision problem. Opposite to people suffering from myopia, farsighted people have difficulty seeing close objects, while objects far away can clearly be observed, because the light focuses actually behind the retina, and light is not focused at all within the eyeball. For objects far needs small angles, they can be clearly captured, while objects near needs to be more sharply refracted, so they come to the retina appearing to be blurry.

Astigmatism. Astigmatism is a common vision problem where the cornea is irregularly shaped. While the normal cornea appear to be like a football, that of an astigmatism patient would appear to be like a spherical ball. When light reflected into the eyes, it refracts in two ways with some focusing on the retina and some focusing in front of or behind the retina. This is why people with astigmatism observe objects with double images.

Presbyopia. Presbyopia is a normal process of aging. It always emerges when people get their 40s or 50s. With aging, the flexibility of the crystalline lens will lose and the lens being less able to change its curvature, so that its ability to accommodate and to produce clear vision of near objects. In some ways, it resembles farsightedness, but with different causes.

Vision problems are not indispositions, which you should pay special attention to. When you find book print looks blurry, you may potentially suffer from farsightedness or presbyopia; when you can not recognize the advertisements far hung in the distance, you may potentially suffer from myopia; when things look a bit blurry at all distances, you may potentially suffer from astigmatic.

When you notice the above symptom, for your eye health, you are in a must to go for an eye doctor to determine your eyes' refractive errors. During the refractive errors diagnosing, a phoropter, a device that positions a variety of different corrective lenses in front of your eyes, will be used to test your eye condition. You will be asked to read an eye chart while looking through the lenses. When you are reading, the eye doctor will constantly change different lenses until you are able to see things in the eye chart clearly. Next your eye doctor, according to your eye condition, will give your corresponding suggestions, either by wearing eyeglasses, or contact lenses or having a laser eye surgery.

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