Refractive [ri-FRAK-tiv] errors occur when your cornea, which is the part of your eye that helps you focus light, doesn’t work the right way.
The four most common types of refractive errors are:
- Astigmatism [uh-STIG-muh-tiz-uhm]. In this condition, the eyes don’t focus light onto the retina [RET-nuh] evenly. The retina is the innermost layer of the eye that receives light and sends an image to the brain so that seeing can happen.
- Presbyopia [prez-bee-OH-pee-uh. This condition involves vision loss that is a result of aging. This condition makes it harder to focus on things that are close to you.
- Hyperopia [hahy-per-OH-pee-uh]. Also called farsightedness, this condition makes things that are far away easier to see than things that are close.
- Myopia [mahy-OH-pee-uh]. With this condition, which is also called nearsightedness, it can be hard to see objects that are far away.
Other eye conditions can be related to refractive errors, such as:
- Cataracts [KAT-uh-rakt]. In this condition, a cloudy film grows over the cornea and can make it hard to see. Cataracts can be treated with surgery.
- Glaucoma [glaw-KOH-muh]. Glaucoma occurs when the optic nerve is damaged by pressure from fluid inside the eye. Untreated glaucoma can result in loss of vision and blindness.
- Blepharitis [blef-uh-RAHY-tis]. If you have this condition, your eyelids can swell up and turn red. You may also wake up with dry eyes or crusted-over eyelashes. Keeping the eyes clean can help prevent the symptoms.
- Nystagmus[ni-STAG-muhs]. If you have this condition, your eyes may move very quickly and without your control. The condition may be inherited [passed down through families), or you might get it later in life.
General symptoms of refractive errors may include:
- Blurred vision
- Double vision
- Bright lights
- Eye strain
- Having a hard time driving at night
The cause of the refractive errors depends on the specific eye problem you have.
- Astigmatism is caused when your cornea bends light differently when it strikes your eyeball. If you have astigmatism your corneas are shaped like ovals instead of circles.
- Presbyopia is a refractive error that is caused by aging. The lens in your eye gets harder as you get older, and this makes it harder for the eye to move the lens to focus on objects that are close. When you are younger, your eye muscles can more easily adjust to seeing things that are close and things that are far away.
- Hyperopia is caused by an eyeball that is too short. It can also be caused by a lens or cornea that isn’t a normal shape.
- Myopia is caused by eyeballs that are too long.It may be inherited, and may also be caused by doing lots of work near to your eyes like reading or writing, though doctors still aren’t sure of the exact cause.
Refractive errors can usually be diagnosed with an eye exam. In an eye exam, an eye doctor will look at your eyes and give you eye tests to check for refractive errors. The doctor may also dilate your eyes, which enlarges your pupils and makes it easier to see if there are any refractive errors present in your eye.
If you notice any of the symptoms of refractive errors, especially a loss or clouding of vision, you should contact your eye doctor.
Refractive errors can be treated using:
- Eyeglasses or contact lenses. These 2 treatment methods work by compensating for the weakness in your eyes. If you have a hard time seeing things that are far away, glasses can magnify your vision and make it easier. Reading glasses can also be purchased without a visit to the eye doctor.
- Surgery. Laser surgery may be performed to reshape the cornea and correct refractive errors.
- Cornea transplant. In this procedure, part of your cornea is replaced with tissue from a donor. Corneal transplants can help get vision back, take away eye pain, and make the eye look better.
If refractive errors are caught early in life, they can be easier to correct. If your child has a hard time seeing, take them to the eye doctor for an eye exam.
It’s hard to know for sure if your eyes are working as they should, and many refractive errors can’t be diagnosed on your own. The best way to be sure is to talk to an eye doctor and get an eye exam.