Free Advertising
- Near-sightedness (Myopia)
Those with myopia see nearby objects clearly but distant objects appear blurred. With myopia, the eyeball is too long, or the cornea is too steep, so images are focused in the vitreous inside the eye rather than on the retina at the back of the eye. See above.
- Far-sightedness (Hyperopia)
Hyperopia, also known as far-sightedness, long-sightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short or when the lens cannot become round enough), causing inability to focus on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance. As an object moves toward the eye, the eye must increase its power to keep the image in focus on the retina. If the power of the cornea and lens is insufficient, as in hyperopia, the image will appear blurred. Refer to below picture.
- Astigmatism
Astigmatism occurs when the front surface of your eye (cornea) or the lens, inside your eye, has a slightly different surface curvature in one direction from the other. Instead of being even and smooth in all directions, the surface may have some areas that are flatter or steeper. When the cornea has a distorted shape, you have corneal astigmatism. When the lens is distorted, you have lenticular astigmatism. Either type of astigmatism can cause blurred vision.
Astigmatism blurs your vision at all distances. Astigmatism is often present at birth and may occur in combination with nearsightedness or farsightedness. The condition tends to remain constant, neither improving nor deteriorating much over time. See illustration below.
- Poor night vision (Nyctalopia)
Nyctalopia is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases. Night blindness may exist from birth, or be caused by injury or malnutrition (for example, a lack of vitamin A). - "Middle-age" sight (Presbyopia)
Presbyopia is a vision condition in which the crystalline lens of your eye loses its flexibility, which makes it difficult for you to focus on close objects.
Presbyopia may seem to occur suddenly, but the actual loss of flexibility takes place over a number of years. Presbyopia usually becomes noticeable in the early to mid-40s. Presbyopia is a natural part of the aging process of the eye. It is not a disease, and it cannot be prevented.
- Crossed eye (strabismus)
Strabismus is a disorder that causes one eye to be misaligned with the other when focusing.
Strabismus is caused by a lack of coordination between the eyes. As a result, the eyes look in different directions and do not focus at the same time on a single point.
In most cases of strabismus in children, the cause is unknown. In more than half of these cases, the problem is present at or shortly after birth (congenital strabismus).
In children, when the two eyes fail to focus on the same image, the brain may learn to ignore the input from one eye. If this is allowed to continue, the eye that the brain ignores will never see well. This loss of vision is called amblyopia, and it is frequently associated with strabismus. See the below picture for better comprehension.
- Lazy eye (amblyopia)
Amblyopia, or "lazy eye," is the loss of one eye's ability to see details. It is the most common cause of vision problems in children.
Amblyopia occurs when the brain and eyes do not work together properly. In persons with amblyopia, the brain favors one eye.
The preferred eye has normal vision, but because the brain ignores the other eye, a person's vision ability does not develop normally. Between ages 5 and 10, the brain stops growing and the condition becomes permanent.
Strabismus is the most common cause of amblyopia, and there is often a family history of this condition.
- Sensitivity to light, eyestrain, headaches, burning eyes
- Cataract
clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light
No comments:
Post a Comment