NearsightednessIt is also known as myopia. It is a condition where a person can see clear up close, but not in the distance. Because myopic eyeballs are generally longer, so instead of the light focusing on the retina, it focuses in front of the retina. A myopic person can read a newspaper, however their distance vision is blurry and requires glasses or contact lenses to make it clear.
FarsightednessIt is also known as hyperopia, is when a person sees better in the distance than at near. In general hyperopic eyeballs are shorter, so light entering the eye focuses behind the retina placing a blurry image on the retina. If the hyperope is not too strong, a young person can still accommodate to see clear at all distances. But in general some hyperopes depending on the degree of prescription will start to need glasses for reading after age 30 to 40.
Farsightedness and presbyopia are often confused, because they both affect close up vision.
PresbyopiaPresbyopia is a condition where the crystalline lens in the eye loses flexibility, and can no longer focus well at near, making reading glasses, bifocals or multifocal lenses necessary. Presbyopia is a natural part of the aging process of the eye. It is not a disease. A person can be both farsighted and presbyopic or nearsighted and presbyopic. Presbyopia makes it hard to do things close up, such as read small prints, use tools, or thread needle. Presbyopia most often starts when you’re 40 to 45 years old. It slowly gets worse until you’re about 60-65 years of age.
AstigmatismOften people feel astigmatism is a bad, progressive disease. Actually astigmatism is caused when light focuses in two points in the back of the eye because it is not in the shape of a sphere “not perfectly round”. An eye with astigmatism has often been described to be in the shape of an egg or football. Astigmatism is a very common condition. Some experts agree that almost all persons have some degree of astigmatism, often present at birth. The degree of astigmatism may remain relatively the same throughout life. Visually, a person with uncorrected astigmatism will often see a faint shadow on letters or objects, images may appear blurred or distorted.
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