Eyesight SimulatorNearsighted vs farsighted
Nearsighted eyes see close things clearly and far things blurry. Farsighted eyes have to work to focus. Young eyes can often do that work, so the blur shows up first when reading, and spreads to distance as focusing weakens with age.
Same strength, opposite sign: nearsighted −2.00 on the left, farsighted +2.00 on the right, both without glasses. Try far and near, and different ages.
Starts to blur beyond about 50 cm, more so farther away.
With +2.00 D at age 30, an average eye can usually still see far things clearly, but things up close, such as a phone, may look blurry. Eyes vary.
This is only a simulation. It is not an eye test and not a substitute for an eye exam. Please consult an optometrist or ophthalmologist about your eyes.
The difference at a glance
| Nearsighted (myopia) | Farsighted (hyperopia) | |
|---|---|---|
| What looks blurry | Things far away | Things up close; with age, far away too |
| Sign on the prescription (SPH) | Minus, for example −2.00 | Plus, for example +2.00 |
| Usual cause | The eyeball is too long from front to back | The eyeball is too short from front to back |
| Effect of focusing effort | Cannot clear distance blur | Can hide the blur, at the cost of effort |
| When it usually shows up | Often starts between ages 6 and 14 | Mild cases may go unnoticed until later in life |
| Glasses lens | Minus (thinner in the middle) | Plus (thicker in the middle) |
The cornea and lens can also play a part in both conditions, not only the length of the eye.
Why the two feel so different
Light from a far object should land on the retina when the eye is relaxed.
- In a nearsighted eye, it lands in front of the retina. The eye has no way to push the focus back, so distance stays blurry. Close objects need less focusing, which is why a phone or a book can look sharp without glasses. A −2.00 eye is sharp out to about 50 cm and blurry beyond.
- In a farsighted eye, it lands behind the retina. The eye can pull it forward by focusing harder (accommodation), the same effort everyone uses to read. A farsighted person spends some of that effort even on distance, and needs extra for reading.
So nearsightedness is mostly a blur problem, while farsightedness is often an effort problem first and a blur problem later.
Why age matters for farsightedness
The eye can focus less as it gets older. The simulator estimates how much focusing an eye of each age can keep up comfortably, from a standard average by age. These are estimates; real eyes vary a lot.
Here is a +2.00 eye reading a phone at 35 cm, which needs about 4.86 D of focusing:
| Age | Focusing the model allows | What the simulator shows |
|---|---|---|
| 8 | about 6.00 D (the formula is capped at 12 D) | Far and near both clear, with effort |
| 30 | about 4.75 D | Right at the limit: the phone just starts to blur, and long reading can be tiring |
| 45 | about 2.50 D | Distance clear, the phone blurs |
| 60 | about 0.25 D | Distance soft too |
Use the age buttons above to watch the same prescription change. In the model, the same +2.00 stays clear at 8 (with effort), starts to blur for reading around 30, blurs clearly for reading at 45, and blurs at a distance by 60.
Farsighted is not the same as presbyopia
Both make close work harder, so they are easy to mix up.
| Farsightedness | Presbyopia | |
|---|---|---|
| Cause | The shape of the eye | The lens gets harder and less flexible with age |
| Who has it | Some people, from birth | Everyone, eventually |
| When it is noticed | Any age; mild cases may go unnoticed | Usually after age 45 |
| Where it appears on a prescription | A plus number in SPH | An ADD number for reading |
A person can have both. In the model, a farsighted eye reaches reading blur at a younger age than an eye without a prescription, because part of its focusing is already spent on distance. See how to read the SPH and ADD on a prescription.
Farsightedness in children
- Many children are farsighted without blurry vision. A child's lens is flexible, so focusing is easy.
- Mild farsightedness often shrinks as children grow. The eye gets longer with growth, and mild farsightedness is reduced or goes away. Some children never need glasses for it.
- Severe farsightedness is a different matter. It can raise the risk of an eye turning in (crossed eyes, or strabismus) or a lazy eye (amblyopia).
- Signs a parent may notice include trouble with close work such as reading, squinting, eye strain or headaches, and an eye that crosses.
A simulator cannot tell whether a child is farsighted or by how much. If you notice any of these signs, see an optometrist or ophthalmologist; farsightedness is checked in a comprehensive eye exam.
Questions
Can you be nearsighted and farsighted at the same time?
Yes, in two ways. One eye can be nearsighted and the other farsighted. And with mixed astigmatism, one direction of the same eye is nearsighted and the other is farsighted; see the astigmatism simulator.
Does farsightedness go away?
In children, mild farsightedness often lessens as the eye grows. In adults the eye no longer grows, and farsightedness tends to become more noticeable with age, because the focusing that hides it weakens.
Which is worse, nearsighted or farsighted?
Neither is simply worse. Nearsightedness blurs distance from the start. Farsightedness can stay hidden for years but costs effort, and shows up more with age. How much either one affects you depends on the amount and on your eyes.
How can I tell from my prescription?
Look at the SPH number. Minus means nearsighted, plus means farsighted. A CYL number means there is also astigmatism. See how to read an eye prescription.
Why can a farsighted person see far away clearly?
Because the eye focuses through it. Young eyes have enough focusing range to cover mild farsightedness at a distance, and often up close too. Glasses take over that work.
This is only a simulation, not a substitute for an eye exam. For your own eyes, consult an optometrist or ophthalmologist.
Sources (checked 2026-10-23)
- National Eye Institute. Nearsightedness (myopia). https://www.nei.nih.gov/eye-health-information/eye-conditions-and-diseases/nearsightedness-myopia — definition, eyeball too long, cornea or lens, usually starts between ages 6 and 14.
- National Eye Institute. Farsightedness (hyperopia). https://www.nei.nih.gov/eye-health-information/eye-conditions-and-diseases/farsightedness-hyperopia — eyeball too short, mild cases may have no symptoms, most farsighted people are born with it, severe farsightedness in children and crossed eyes or amblyopia, checked in a comprehensive eye exam.
- American Academy of Ophthalmology. Hyperopia (farsightedness). https://www.aao.org/eye-health/diseases/hyperopia-farsightedness — most children are farsighted without blurry vision, flexible lens, mild farsightedness reduced or eliminated as the eye grows, some children outgrow it, signs (close tasks, eye crossing, squinting).
- National Eye Institute. Presbyopia. https://www.nei.nih.gov/eye-health-information/eye-conditions-and-diseases/presbyopia — lens gets harder and less flexible, usually after age 45, everyone gets it.
- Model numbers: the focusing an eye can keep up is half of Hofstetter's average maximum for its age (18.5 − 0.3 × age diopters, capped at 12 D). See how the simulator works.
