What Is a Refraction Test?
February 9, 2022
A refraction test is a simple eye exam that can help diagnose and monitor many eye conditions. This test measures how well your eyes focus light on the retina, the back of the eye where images are projected. A 20/20 value means a person sees at 20 feet what a healthy eye would see at 20 feet. The refractive power of the eye is how images come into focus. When one does not have a 20/20 vision, they are considered to have a refractive error.
Refraction tests typically involve a tool called a phoropter. The doctor uses the phoropter to show you different strengths of lenses to determine your prescription. The doctor will then use this information to determine if there’s anything wrong with your vision or whether glasses or contact lenses are needed.
Why Is This Test Used?
This test is used by an ophthalmologist or optometrist to determine if you need glasses, contact lenses, surgery, or no further treatment.
The test results help diagnose:
1) Myopia. A refraction test can help detect myopia, also known as nearsightedness. Myopia occurs when the eye is too long, or the cornea has too much curvature, causing light rays to focus in front of the retina instead of on it. This causes distant objects to be blurry, while close objects may appear normal.
2) Hyperopia. A refraction test can help detect hyperopia, also known as farsightedness. Hyperopia occurs when the eye is too short, or the cornea has too little curvature, causing light rays to focus behind the retina instead of on it. This causes distant objects to be blurry, while close objects may appear normal.
3) Astigmatism. A refraction test also can detect astigmatism. Astigmatism occurs when the eye’s cornea is irregularly curved, causing light that passes through it to be doubled or slanted and vision to be blurred at all distances.
4) Presbyopia. Age-related farsightedness or presbyopia can be corrected with progressive, bifocal, or reading glasses. In some cases, contact lenses may help. It occurs when the aging lens inside your eyes loses elasticity, making it harder to focus on close objects.
5) Amblyopia. If a child has amblyopia, also called lazy eye, they may have problems seeing clearly during a refraction test. This may improve in some cases with glasses or patching.
Who Should Be Tested?
A complete eye examination should be performed at least once in a child’s life. Your ophthalmologist or optometrist should test preschool and school-aged children to ensure they have normal vision and no serious vision problems. If you wear eyeglasses, your eye doctor will typically check the strength of your prescription annually, or if you experience vision changes.
Also, if you have diabetes, glaucoma, high blood pressure, cataracts, or any other eye disease or have had an eye injury, your doctor usually will recommend more frequent refraction tests. If you are in the early stages of certain eye conditions, your doctor may recommend more frequent refraction tests to monitor changes in vision over time.
What Happens During the Test?
The technician or doctor will ask you to sit in a special chair facing a tool called a phoropter. You’ll be asked to focus on an eye chart or pictures. Then, you’ll read the letters (or look at the picture) through different lenses until your vision is clear and sharp.
Your doctor uses the information from the test to determine whether you need corrective lenses, which type of lenses are best for you, and what power or strength should be assigned to them.
Your doctor will ask you to read letters on an eye chart while they watch your eyes through a machine called a phoropter. They may use lenses in the phoropter to measure and determine your prescription.
Schedule an Appointment
If your vision isn’t as clear as it once was, it’s time to schedule a refraction test. Call Anh Nguyen Ophthalmology at (703) 534-4393 or contact us online.
