How are Some people Nearsighted and Others Farsighted?

Question

As people lose their vision, what makes some of them nearsighted and others farsighted. I can't understand how a person can be able to see an object that is far away more clearly than one that is up close to their face. How does your vision deteriorate like that?

Answer 1

Well it’s really depending on what age group you are talking about. In younger people it’s not actually a deterioration of vision; it is just a natural change that happens especially with growth spurts.
When a person is farsighted (hyperopic) their eyeball is too short and the light coming into their eyes is focusing behind the retina. The light needs to focus on the retina in order for a person to be able to see clearly. When a person is nearsighted (myopic) their eyeball is too long and the light coming into their eyes comes into focus in front of the retina! Astigmatism is due the cornea or crystalline lens being shaped more cylindrical like a football then spherical like a baseball.

So basically people with different types of refractive errors (nearsighted, farsighted and astigmatism) are due to their eyes or parts of their eyes being sized/shaped differently.

As a person ages the crystalline lens in the eye that normally changes shape to focus on objects at near starts to loose its elasticity. As it looses its ability to flex we begin loose our ability to focus on objects at near (reading). This usually starts to become noticeable around age 40 and reading glasses are needed to read! This is a natural part of aging and has nothing to do with being nearsighted/farsighted!
Actual detoration of vision usually only happens in older persons with age related conditions such as macular degeneration or in medical illnesses!
Anyways hope this helps a bit :)

Answer 2

There are three primary elements that provide refractive error.

The refractive power of the cornea (clear front of the eye)
The refractive power of the crystalline lens
The length of the eye.

Axial myopia (nearsighted, shortsighted) vision is when the eye is longer than normal, causing the focus point of the light entering the eye to be in front of the retina (light sensitive membrane inside the back of the eye). Axial hyperopia (farsighted, longsighted) vision is when the eye is shorter than normal, causing the focus point to be behind the retina.

Axial length is the most common reason why people are nearsighted and some are farsighted.

You may be confusing nearsighted/farsighted with vision quality. Even when a person is emmetropic (not myopic or hyperopic) the quality of vision can vary dramatically.

The density of the cells at the macula where central vision is formed can be different from person to person. The quality of the light after passing through the cornea, crystalline lens, and the internal fluids can vary. The most that human vision can provide is about 20/10 visual acuity. That would mean seeing an object 20 feet away with the clarity a normal sighted person would see that object at 10 feet away. Even when the optics of the eye are perfect, the brain needs to be able to appropriately interpret the signals into sight. Some brains are better at this than others.

Answer 3

Mos people have pretty regular Corneas, some not, but most do. A typical focus of your cornea and lense system would be at a given point in the eye. Ideally this would focus on your retina, which is what your brain uses to see. A farsighted person has a short eyeball so light does not have room to focus on the retina becuase th retina falls way in front of where it should be normally. This means the person does not see well up close at all, but it does not affect there distance as much, ti does affect it, but not as much as the near. A near sighted person has the opposite problem in that their eyeball is too long and the focus falls way in fromt of the retina where it is suposed to be, but the eyeball being long has pucshed the retina away form where the focal point would be. These people can see up close really well, because it is like having a magnifying glass inside your eye of a high power, you see distance realy bad the up close is great! So, astigmatism means that you have a funky shape to your cornea, or your lense in your eye, and the light focuses at two diferent points instead of one and that makes things blurry and esily strained for the eye. People can have farsightedness or nearseghtedness alone or mixed with astigmatism. Now, people with Bifocals have a different problem in that most of the time it is the lense in their eye that stops doing up close focusing no matter what the distance problem is, so bifocal powers are needed for that. It seams complicated, and it is, but once you understand how the eye's light system works, it is not that big of a deal. Did I just make it worse? Well, it is a hereditary thing for the most part, it is how we are made, not something that is controlable. More than 2/3 of the worlds population need some sort of correction. People with "normal" vision are those that need glasses. Those with perfect vision are in the minority, and not normal.

Answer 4

It's mostly due to the length of your eye (axial length). As we grow, our 'eyeballs' do too. No one knows why some people end up with longer than average eyeballs or shorter than average eyeballs. To see clearly, light entering the eye needs to reach to the back of the retina.

Long eyes = myopia (nearsightedness) Light stops at a point in front of the retina.

Short eyes= hyperopia (farsightedness). Light stops behind the retina.

For a myope, it's like looking through a magnifying glass for distance. For a hyperope, it's like looking through binouculars to read. The prescription in glasses is actually a way to re-refract the light entering your eye.

Hyperopia is often confused with presbyopia (literally, latin for 'old eyes'). Presbyopia becomes very noticeable as we get to about 40-45 years old. The lens inside the eye loses its' elasticity gradually, reacting slower and slower to accommodate when you're reading.

Answer 5

The eye focuses on a certain part of the back of the eye. If the focal point falls in front of that certain area, the person can see better if an object is up close but if the focal point falls behind that certain area, then the person can see better looking far away.

Vision deteriorates for a number of different reasons: Genetics, environment, personal hygiene practices (contacts/solution/eye drops/etc), exposure to pollutants (allergies/smog/exhaust fumes/etc), disease, and age. Maybe you were born with bad eyes, maybe your vision worsened over time. There is no one reason that vision goes bad. I hope that you are one of those fortunate few that have good vision.

Answer 6

well, vision can decrease in a number of ways. People can lose their vision through an injury or old age. Other causes of vision loss are diseases such as glaucoma, ROP, macular degeneration, or other diseases. Nearsighedness is caused when the eye is a longer shape than usual. Light is focused in front of your retna causing objects that are far away to appear blurry. Farsightedness is caused when the eye is when the eye is curved to little. The light is focused behind the eye causing objects that are close up to appear blurry.
hope this helped!!!

Answer 7

It's because with degeneration in different parts of the eye the light bounce in different area of the retina causing near&farsightness

Answer 8

It may be inherited from your mom or dad. The genes you know. Health also plays a big part. Having to wear glasses is natural and it is a sign of aging too. it is so important to protect your eyes, and your ears from loud noises too.

Answer 9

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Answer 10

Nearsightedness and farsightedness are cause by the shape of certain parts of your eye. As you get older or put more strain on your eyes it will cause changes to the lens and cause it to function differently causing nearsightedness or farsightedness.