Eyeballs change shape why

May develop following an eye injury or eye surgery. It can occur due to a relatively rare condition called keratoconus in which the cornea becomes progressively thinner and cone-shaped. It can decrease or increase over time. Symptoms Blurred vision at any distance. Eye discomfort. Diagnosis A doctor of optometry can diagnose astigmatism through a comprehensive eye examination.

This examination may include: Visual acuity. When you read letters on a distance chart, you are measuring your visual acuity. The top number is the standardized testing distance 20 feet and the bottom number is the smallest letter size read.

A keratometer is the primary instrument used to measure the curvature of the cornea. By focusing a circle of light on the cornea and measuring its reflection, it is possible to determine the exact curvature of that area of the cornea's surface.

This measurement is particularly critical in determining the proper fit for contact lenses. A corneal topographer—which is gaining use—generates a contour map of the cornea and provides even more detail of the cornea's shape. Using an instrument called a phoropter, your doctor places a series of lenses in front of your eyes and measures how they focus light.

This is performed using a handheld lighted instrument called a retinoscope or an automated instrument that evaluates the approximate focusing power of the eye. Based on your responses, the power is then refined to determine the lenses that allow the clearest vision.

Despite improved technology, patient input remains integral in determining vision needs. Treatment Eyeglasses. People with astigmatism primarily choose eyeglasses to improve their vision. The eyeglasses contain a special cylindrical lens prescription that compensates for astigmatism. This provides additional power in specific parts of the lens. Generally, a single-vision lens is prescribed to provide clear vision at all distances. However, patients over age 40 who have presbyopia may need a bifocal or progressive addition lens.

Contact lenses. Some people will have better vision with contact lenses rather than eyeglasses. Because the eye's structure is so complex, though, a lot of things can go wrong. Some of the most common eye problems are refractive errors.

These are the problems that eye doctors check for routinely in a vision test. Refraction means bending of light rays to focus the light coming from an image.

Refractive errors are problems with the focusing of the eye, because of the way the eye is shaped, which causes the image you see to be blurred. In astigmatism uh-STIG-muh-tih-zum , there's a problem with the curve of the cornea. This causes part of the eye's image to be blurry. Corrective lenses such as contact lenses or glasses can usually correct vision in people with astigmatism. Also called nearsightedness or shortsightedness, myopia my-OP-ee-uh happens when the eye focuses the image of an object in front of the retina instead of directly on it.

In most cases, people can't see well far away, but can see objects clearly close up. The condition tends to get somewhat worse through childhood and adolescence, but stabilizes in adulthood. People with this condition may need to wear glasses or contacts to correct their vision. Laser eye surgery is sometimes used in adults to correct nearsightedness permanently by changing the shape of the cornea. Laser surgery is not used for teens because the eye may still be growing and the refractive error changing.

Also called farsightedness or longsightedness, hyperopia hy-per-OP-ee-uh happens when the incoming image is not focused on the retina, but behind it. This may make it difficult to see close objects clearly, with far-off objects seen more easily. Many younger children are hyperopic, but because of the ability of the eye to focus itself, may not need glasses to correct this. Glasses or contact lenses can correct this problem in kids and teens when needed.

Most adults develop a form of farsightedness called presbyopia as they get older. Reviewed by: Larissa Hirsch, MD. Larger text size Large text size Regular text size. How Do We See? The wall of an eyeball has three layers, rather like the layers of an onion: The sclera SLEER-uh is the protective layer. This tough, fibrous tissue surrounds the eyeball and attaches to the cornea, which is the clear front surface of the eye.

What we see as the white of the eye is the sclera. Over the sclera lies the conjunctiva, a clear skin layer that protects the eye from becoming dry. The choroid KOR-oyd is the middle layer that contains blood vessels that deliver oxygen and nutrients to the inside parts of the eye. The retina RET-nuh , the innermost of the three layers, lines the inside of the eyeball. The retina is a soft, light-sensitive layer of nervous system tissue.

The optic nerve carries signals from the retina to the brain, which interprets them as visual images. Astigmatism in 1 eye may cause lazy eye where the vision does not develop properly. It's important this is spotted early so it can be treated. Take your child for regular eye tests. Astigmatism, as well as short-sightedness or long-sightedness, may affect their reading or concentration. Teenagers with astigmatism should also have regular eye tests to check for an eye condition called keratoconus.