What is a Refraction Eye Exam?
A refraction is the part of an eye exam that measures one’s prescription for eyeglasses. The examination begins by assessing an individual’s distance vision and near vision. In those over 40 years of age, a refraction is used to determine the power for reading glasses. If your uncorrected vision (without glasses or contact lenses) is normal, then the refraction power is zero (plano) and your vision should be 20/20 (6/6). 20/20 (6/6) is normal vision. A patient’s refractive error can also be called their “prescription.” The prescription is the combination of numbers that describe the lens powers needed for the patient to see clearly. A refraction is only one part of a comprehensive eye exam.
Key Takeaways
- A refraction is the part of the eye exam that determines the prescription for glasses.
- One sees 20/20 if they have normal vision with a refraction of plano (0).
- A doctor presents the patient with a series of choices to determine the prescription, “1 or 2?”
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Understanding Refraction Eye Exam
The patient is asked to look through the phoropter and view the eye chart. The phoropter contains many lenses and is used to determine the lens combination that allows the individual to see 20/20 on the chart. The eye doctor will then ask if the chart appears more or less clear when different lenses are in place. The results depend on the patient response, but there is a system in place to ensure accurate results. This is the part of the eye exam where the patient is asked, “which is better 1 or 2?”
Results of a Refraction Eye Exam
The result of a refractive eye exam can be myopia, hyperopia, presbyopia, astigmatism or a combination. A refraction is separate from an evaluation of eye health.
Myopia
Myopia or being nearsighted means one is unable to see in the distance. In a patient with myopia, the eye is longer than normal. When the light enters the eye, it falls in front of the retina. Patients with myopia need minus lenses in order to focus the light on the retina and see clearly in the distance.
Hyperopia
Hyperopia or being farsighted means one is unable to see at near or may have to work harder to see at near. In a patient with hyperopia, the eye is shorter than normal. When the light enters the eye, it falls behind the retina. Patients with hyperopia need plus lenses in order to focus the light on the retina and see clearly up close.
Presbyopia
Presbyopia is an age-related change in the lens and the ciliary body within the eye. The structures lose the ability to change shape resulting in the inability to focus on near objects up close.
Astigmatism
Astigmatism is commonly described as the cornea being similar to an egg or football. The curves are of a different power in opposing meridians. Astigmatism can affect one’s vision at every distance resulting in a slight blur, halo or ghost images around letters and lights.
What can’t a Refraction Eye Exam Diagnose?
A refraction cannot diagnose any ocular disease or pathology. It can tell an eye doctor if there is a reduction in vision and they use that information to look for a reason for the vision decline including cataracts, glaucoma, age-related macular degeneration or dry eye disease.
Is A Refraction Eye Exam Covered by Insurance?
Vision insurance may cover a refraction eye exam, but many medical insurances including Medicare do not cover a refraction eye exam. Patients will be billed for the refraction component of the eye exam.
