折射

定义

A refraction is an eye exam that measures a person's prescription for eyeglasses or contact lenses.

选择的名字

Eye exam - refraction; Vision test - refraction; 折射

如何执行测试

This test is performed by an ophthalmologist or optometrist. Both of these professionals are often called an "eye doctor."

You sit in a chair that has a special device (called a phoroptor or refractor) attached to it. You look through the device and focus on an eye chart 20 feet (6 meters) away. The device contains lenses of different strengths that can be moved into your view. The test is performed one eye at a time.

• The eye doctor will then ask if the chart appears more or less clear when different lenses are in place.The results depend on your responses.
• Then, a device shines specialized light into your eyes and also determines your refraction. Responses from you are not needed. Each type of refraction has their own benefits.

如何准备考试

如果你戴隐形眼镜, ask the doctor if you need to remove them and for how long before the test.

考试的感觉如何

没有不适.

为什么要进行测试

This test can be done as part of a 常规眼科检查. The purpose is to determine whether you have a refractive error (a need for glasses or contact lenses).

For people over age 40 who have normal distance vision but difficulty with near vision, a refraction test can determine the right power of reading glasses.

正常的结果

If your uncorrected vision (without glasses or contact lenses) is normal, then the refractive error is zero (plano) and your vision should be 20/20 (6/6).

A value of 20/20 (6/6) is normal vision. This means you can read 3/8-inch (1 centimeter) tall letters at 20 feet (6 meters). A small type size is also used to determine normal near vision.

异常结果意味着什么

You have a refractive error if you need a combination of lenses to see 20/20 (6/6). Glasses or contact lenses should give you good vision. If you have a refractive error, you have a "prescription." Your prescription is a series of numbers that describe the powers of the lenses needed to make you see clearly.

If your final vision is less than 20/20 (6/6), 即使有镜片, 然后可能还有另一个, non-optical problem with your eye.

The vision level you achieve during the refraction test is called the best-corrected visual acuity (BCVA).

Abnormal results may be due to:

• 散光 (abnormally curved cornea causing blurred vision)
• 远视 (远视)
• 近视 (近视)
• 老花眼 (inability to focus on near objects that develops with age)

Other conditions under which the test may be performed:

• 角膜溃疡和感染
• 由于……而丧失锐利的视力 黄斑变性
• 视网膜脱离 (separation of the light-sensitive membrane (retina) in the back of the eye from its supporting layers)
• 视网膜血管阻塞 (blockage in a small artery that carries blood to the retina)
• 色素性视网膜炎 (an inherited disorder of the retina)

风险

There are no risks with this test.

注意事项

You should have a complete eye examination every 3 to 5 years if you have no problems. 如果你的视力变得模糊, 恶化, or if there are other noticeable changes, 马上安排一次考试.

After age 40 (or for people with a family history of 青光眼), eye exams should be scheduled at least once a year to test for 青光眼. Anyone with diabetes should also have an eye exam at least once a year or as recommended by their provider.

People with a refractive error should have an eye exam every 1 to 2 years, 或者当他们的视野改变时.

参考文献

查克RS, 邓恩SP, Flaxel CJ; American Academy of 眼科学 Preferred Practice Pattern Committee, 等. Comprehensive adult medical eye evaluation preferred practice pattern. 眼科学. 2021;128(1):1-29. www.aaojournal.org/article/S0161-6420(20)31026-5/fulltext. 2020年11月12日发布.

Jacobs DS, Afshari NA, Bishop RJ, 等. Refractive errors preferred practice pattern. 眼科学. 2023;130(3):P1-P60. PMID: 36543603 pubmed.ncbi.nlm.国家卫生研究院.gov / 36543603 /.

Jacobs DS, Lee JK, Shen TT, 等. Refractive surgery preferred practice pattern. 眼科学. 2023;130(3):P61-P135. PMID: 36543604 pubmed.ncbi.nlm.国家卫生研究院.gov / 36543604 /.

吴一. 临床折射. 见:Yanoff M, Duker JS编. 眼科学. 6日艾德. Philadelphia, PA: Elsevier; 2023:chap 2.3.