November 9, 2017
Refractive errors are one of the most common and correctable causes of visual impairment. This happens when the eye cannot focus light properly on the retina, which is the light-sensitive tissue lining the back of the eye. Nearly 42% of Americans ages 12-54 are nearsighted (myopia). This is an increase from 25% percent in 1971! Farsightedness (hyperopia) is far less common. It affects just 5-10% of people in the U.S. Both of these are refractive errors – a person who is nearsighted can see close objects clearly but has more difficulty seeing distant objects. A person who is farsighted can see distant objects clearly but has problems seeing close objects.
Nearsightedness occurs when the eyeball is too long from front to back, or when the cornea (clear front cover of the eye) is steeply curved. When this occurs, the light entering the eye focuses in front of the retina, instead of on its surface. In about 10% of nearsighted people, the condition progresses in severity. Signs of myopia include:
You are farsighted when your eyeball is too short from front to back, the cornea is not curved enough, or the lens sits farther back in the eye than normal. As a result, light entering the eye focuses behind the retina, rather than directly on its surface. Many infants are farsighted at birth, however, they grow out of it and far more children end up nearsighted due to environmental factors. Signs of farsightedness include:
A doctor uses a standardized Snellen chart placed 20 feet away to test visual acuity. During the exam, you read progressively small letters, one eye at a time until you can no longer clearly distinguish them. “Normal” or 20/20 vision means you can clearly read specific letters from 20 feet away. If you have 20/40 vision, this means you can read letters from 20 feet that most people see clearly when they are 40 feet away. The EyeQue Insight is an at-home visual acuity screener that allows anyone ages 6 and above to check the clarity of vision in under 3 minutes. This number only indicates visual acuity, so a different measuring device is required to obtain a prescription correction.
A device called a phoropter or refractor is a quick means of determining the refractive error to obtain a prescription. You view this device that contains lenses of different strengths while an eye doctor tests your vision. Your eye doctor will ask you which of the two combinations of lenses looks clearer until he or she finds the best correction for each eye. The EyeQue Personal Vision Tracker lets you obtain the same spherical, cylindrical, and axis figures that your eye doctor uses to generate a prescription. The Personal Vision Tracker measures the amount of correction needed for light to focus correctly on your retina.
When you have a piece of paper with mysterious numbers and abbreviations, indicating your eyeglass or contact lens prescription, you may have no idea what it means.
A diopter is a standard unit of measurement on eyeglass prescriptions. A negative diopter number specifies nearsightedness. A positive number indicates farsightedness. A diopter designates how powerful a lens is needed to properly focus light on a person’s retina. Many people have astigmatism in addition to myopia or hyperopia. In astigmatism, the cornea has a curvature imperfection, or the lens is distorted, resulting in both near and far objects appearing blurry.
The VisionCheck is our second-generation Personal Vision Tracker. You can test your refractive error from anywhere and order glasses online with the results. The VisionCheck is different from the PVT in that it includes:
The PDCheck allows you to measure your pupillary distance within seconds.
With the award-winning VisionCheck, you can test your vision, measure your pupillary distance, and order glasses online with your results.Order Now!