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July 2, 2020
3 min. read

Conditions in Ophthalmology: Nearsightedness, Farsightedness, and Astigmatism

ND Medina

Eyes: we?ve got ?em and we use ?em to see with. But there are many different ways in which our eyes work, and some eyes work differently from other eyes. In this blog, we discuss nearsighted eyes, farsighted eyes, and astigmatism to see how and why eyes with these conditions work the way they do.

Nearsightedness

Nearsightedness, also known as myopia, is a condition where things far away from you are blurry even though things close to you are clear.

There are two parts of the eyeball that come into play. One is the cornea, which is the clear and dome-shaped front surface of your eye. The other is the lens, which is a small, clear, rounded structure. There is also the retina, the light-sensitive surface at the back of the eye, onto which images are formed through the bending of light via the cornea and lens.

If the eye is shaped ideally, each of these focusing elements is perfectly smooth and curved, like a marble. A cornea and lens that are perfectly curved will bend (refract) all incoming light to create a sharply focused image directly on the retina at the back of your eye.

However, if your cornea or lens isn't evenly and smoothly curved, light rays aren't refracted properly. This causes what is known as a refractive error.

Nearsightedness is a refractive error caused due to the shape of the eye, which means either your eyeball is longer than normal or your cornea is too steeply curved. This makes light rays to bend incorrectly and focuses images in front of your retina rather than on your retina.

According to the Mayo Clinic, symptoms of nearsightedness include:

? Blurry vision when looking at distant objects ? The need to squint or partially close the eyelids to see clearly ? Headaches caused by eyestrain ? Difficulty seeing while driving a vehicle, especially at night (night myopia)

You may have nearsightedness in one or both eyes, just to keep things interesting for your optometrist.

Farsightedness

Farsightedness, also known as hyperopia, is a condition where things far away can clearly be seen, but things up close are blurry. The degree of farsightedness is what influences your focusing ability. This means that people with severe farsightedness may only be able to see things a very great distance away, while those with mild farsightedness may be able to see things closer to them.

According to the Mayo Clinic, symptoms of farsightedness include:

? Nearby objects may appear blurry ? You need to squint to see clearly ? You have eyestrain, which includes burning eyes and aching in or around the eyes ? You experience general eye discomfort or a headache after a prolonged interval of conducting close tasks, such as reading, writing, computer work or drawing

Farsightedness occurs when your eyeball is shorter than normal or your cornea is not curved enough. This causes the opposite effect of nearsightedness. Interestingly, in adults with farsightedness, both near and distant objects can be blurred. You can also, just to be spicy, have just one farsighted eye.

Astigmatism

Astigmatism is a common medical condition that causes blurred vision. It happens when the cornea or the lens inside the eye is irregularly shaped, which prevents light from focusing properly on the retina.

In astigmatism, an irregularly shaped cornea or lens prevents light from focusing properly on the retina. This means vision becomes blurred at any distance. Astigmatism frequently occurs with other vision conditions like myopia (nearsightedness) and hyperopia (farsightedness).

Together, these vision conditions are referred to as refractive errors because they affect how the eyes bend, or refract, light.

Astigmatism is often hereditary and is usually present from birth. The severity can change over time. As with nearsightedness and farsightedness, eyeglasses or contact lenses can correct astigmatism by correcting the way light enters the eye. There are also surgical options, such as laser eye surgery.

If you feel you or your child may be suffering from refractive errors of the kind described above, make sure to reach out to an optometrist for a comprehensive eye examination. This kind of examination will include a visual acuity test (the eye chart with letters you read off of), keratometry or topography to map the shape of the cornea, and refraction tests using an instrument called a phoropter (the big, funny-looking machine with all the lenses that the examiner switches between so you can tell the examiner which lens works best for you). With the results from these tests, you and your optometrist can proceed to determine which treatment options work best for you and your lifestyle.

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