If your vision has changed recently, you may need glasses to improve your sight. (Learn More)

Getting regular eye exams, especially after you turn 40 years old, means you have consistent monitoring of your vision changes over time and better prescriptions to suit your needs. (Learn More)

If you do not have the time to get an eye exam and are concerned about your vision changes, an online or printable at-home test may help you get an idea of your vision change, but it cannot diagnose your vision with full accuracy. (Learn More) If you are middle aged or older, you could also get over-the-counter reading glasses to improve your vision. (Learn More)

However, the best way to take care of your eyes is to be diagnosed by an eye doctor.

woman with farsightedness

How Do You Know You Need Glasses? 

 

Eyeglasses are one of the oldest methods of correcting vision problems. A frame holds two glass or plastic lenses that modify how light refracts into your eye, so you can see clearly despite a refractive error.

Glasses are among the most common forms of eyewear to correct sight, adding or subtracting power to manage nearsightedness (myopia), farsightedness (hyperopia), misshapen corneas (astigmatism), or farsightedness associated with age (presbyopia).

Most people develop vision problems as they get older, but for many people, refractive errors begin in childhood. Often, eye diseases like glaucoma and cataracts manifest refractive errors, so you may initially think your eyesight is getting worse due to age.

Because there are several potential causes of changing vision, it is important to go to an optometrist for a full eye exam, diagnosis, and referral to other practitioners if necessary. You may be able to understand some of your vision problems on your own, thanks to the internet, but again, a professional exam is always recommended.

Glasses Prescriptions: How Your Vision Correction Is Measured Over Time

 

When you visit an optometrist, they will measure each eye strength separately because the human eye changes at different rates.

The Federal Trade Commission (FTC) monitors optometrists and ophthalmologists through the Eyeglass Rule and the Contact Lens Rule, requiring your eye doctor to give you your lens prescription at the end of the exam for no additional fee, whether or not you ask for a prescription for glasses or contact lenses. You can take your prescription to any provider of glasses or contact lenses, including online services, and you should never be required to fill this prescription at your specific optometrist’s office.

The power of your eye’s visual strength is measured in diopters, reflecting the amount of change in lens shape needed to clearly focus images onto your retina. As your vision changes, diopter measurements will adjust by 0.25 as the standard increment. Your eyes are referred to differently.

  • Oculus dexter is the right eye, abbreviated as RE.
  • Oculus sinister is the left eye, abbreviated with LE.

These terms come from Latin root words, but you may see them on your prescription to indicate your eyes. You may also see measurements.

  • Sphere: This number reflects your nearsightedness or farsightedness. This will appear on your prescription as “S.”
  • Cylinder: This number indicates level of astigmatism, which changes the shape of the eye from round to cylindrical. Your prescription reflects this measurement as “C.”
  • Axis: This number measures the degree of astigmatism. This word will be written out on your prescription.

The typical format for writing these numbers on your prescription is S x C x Axis.

hyperopia vs. normal vision graphic

Since hyperopia, myopia, and astigmatism change the cornea and the rest of the eye’s shape in different ways, you will need different lens shapes to refract light. These shapes include:

  • This shape is thin at the center and thicker at the edges, which helps to adjust nearsightedness. Prescription diopters have a “-“ sign in front of them.
  • The opposite of concave, convex lenses are thickest at the center and thinner at the sides to correct farsightedness — either hyperopia or presbyopia. Prescription diopters have a “+” in front of them
  • These lenses typically curve more in one direction than another to correct for astigmatism.

Even if you have “perfect” vision — or 20/20 vision, meaning you can see clearly 20 feet away from you — you should still undergo annual eye exams to maintain your eye health. Eye health can reflect general health, and comprehensive visual exams every year can show if there are changes in your cornea, retina, fluid pressure, and other important parts of your eye.

If you do not have any previously diagnosed eye conditions, you should consider getting eye exams at certain frequencies based on age.

  • Babies: The first eye exam should occur at 6 months old, with another at 12 months (1 year).
  • Children: Between 3 and 5 years old, the child should go in for an eye exam at least once. Then, the child should have an eye exam at 6 years old or before first grade. Eye exams should be annual after that until age 18.
  • 20 to 39 years old: If you have no preexisting eye conditions, including refractive errors, you should get an eye exam at least every 5 years.
  • 40 to 54 years old: Once you reach middle age, it is important to have eye exams every 2 to 4 years because several vision changes begin at this point in your life even if you have not had vision problems before.
  • 55 to 64 years old: Eye exams are needed every 1 to 3 years to monitor your eye health for serious conditions, including cataracts.
  • 65 and older: Getting an eye exam every 1 to 2 years monitors progressing eye changes for older adults.

Your optometrist or ophthalmologist will perform several tests during your routine eye exam to determine if your eyes are changing, how much they are changing, and why.

Many people are choosing to check their eyes online instead of going to an eye doctor. This process can get you started, but optometrists and ophthalmologists have tools at their disposal that allow for more thorough diagnoses.

At-Home and Online Tests Cannot Diagnose Underlying Conditions

woman receiving glasses in front of eye exam

There are a few charts that can be used online to get a general idea of your visual problems or changes. For example, color vision charts can accurately tell you whether you have colorblindness or not; however, these tests do not provide treatment, and they are not a legitimate prescription. You will still need to see a medical professional to understand how colorblindness may be associated with your general health.

The American Academy of Ophthalmology (AAO) offers help to perform tests at home for children or adults and get the most accurate readings possible. Sit 10 feet away from a printed or onscreen Snellen Eye Chart, which starts with a large “E,” and record which lines you are able to read without any visual correction. Then, cover one eye and read the lines; cover the other eye and read the lines; and record your results. Your eyes most likely have minor differences.

You may also consider a printable diopter reading test, which you will then hold 14 inches away from your eyes. Attempt the top line, which has the smallest print, without any glasses or contact lenses; continue down the chart until you can find a line that you can read clearly. The number to the right of the line indicates what prescription power you need. If you need less than +3.00, you may be able to find reading glasses over the counter.

There are other vision tests available through several online companies, including one for astigmatism, but professional eye doctors question the accuracy of these tests. Still, many of the services will offer to send your results to a professional optometrist or ophthalmologist in your area for review after you pay a small fee. If you choose not to pay the fee, but do notice that you have poorer vision than you expected, this indicates that you should see an eye doctor in person.

Most people develop a refractive error at some point, but sometimes, conditions like glaucoma or cataracts can cause changes in your vision. These conditions must be monitored, or you can go blind.

Reading Glasses for Presbyopia: Over the Counter or Prescription?

 

If you have presbyopia and have not developed other refractive errors earlier in life, your optometrist may recommend purchasing over-the-counter reading glasses. Typically, your optometrist will recommend reading glasses power based on your age.

  • 40 to 44 years old: You will use a power between +0.75 to +1.00 diopters to adjust your presbyopia.
  • 45 to 49 years old: Typically, this age group will need +1.00 to +1.50 diopters.
  • 50 to 54 years old: As presbyopia continues, this age range will need between +1.50 and +2.00 diopters.
  • 55 to 59 years old: For this age group, +2.00 to +2.25 diopter reading glasses are typically recommended.
  • 60 years old and older: For older adults, +2.25 to +2.50 diopters can adjust more progressed presbyopia.

Nonprescription reading glasses are sold over the counter with powers up to +3.00. After passing this convex lens number, you will need a prescription for reading glasses. Experts recommend that you pick the reading glasses with the lower power if you have two pairs of OTC glasses that correct your vision in about the same range. Wearing corrective lenses that are too powerful, even a little bit, for your eyes can cause eye strain, headaches, and make your vision worse faster.

You should also consider getting several pairs of reading glasses with different powers to help you perform different tasks, including working on a computer, watching television, and driving.

Over-the-counter reading glasses, or readers, may work for you for a little while, but if you find that OTC glasses improve your vision, you should get a comprehensive eye exam soon. This exam means you can get a prescription for glasses. Your vision will be accurately corrected based on unique biological factors.

Reasons you will need to see an optometrist for a prescription instead of purchasing OTC glasses include:

  • Your pupils may not line up with store or online glasses, so you need a custom fit.
  • You have an underlying medical condition that changes your refractive error faster than average.
  • You have different diopter powers in each eye. OTC reading glasses have the same power in each eye, but most people naturally develop slightly different powers in each eye as their vision changes.
  • You have astigmatism, which OTC reading glasses do not correct for.

OTC glasses are made with less precision and tend to be lower-quality glass. These distortions can cause long-term problems with your eyesight

Overall, it is best to see an optometrist every few years or as soon as you have questions or concerns about your vision quality. It is likely that you have a normal refractive error, but you may have a different condition in your eyes. You may need a different approach than over-the-counter reading glasses to help you.

Establishing a relationship with an optometrist or ophthalmologist means you can have your vision monitored by professionals as you age. This is incredibly important.

References

 

Eyeglasses for Vision Correction. (December 12, 2015). American Academy of Ophthalmology (AAO).

Prescription Glasses and Contact Lenses. (April 2016). Federal Trade Commission (FTC) Consumer Information.

Eyeglasses and Contact Lenses. University of Rochester Medical Center, Health Encyclopedia.

How to Read Your Eyeglass Prescription. (December 7, 2017). WebMD.

20/20 Vision? Why You Still Need an Eye Exam. Aetna Health Insurance.

Recommended Eye Exam Frequency for Pediatric Patients and Adults. American Optometric Association (AOA).

Home Eye Test for Children and Adults. (December 21, 2016). American Academy of Ophthalmology (AAO).

Snellen Eye Chart. All About Vision.

Find Your Reading Glasses Power. The Fine Print Blog.

The Doctor Will “See” You Now: Online vs. In-Person Vision Tests. (March 15, 2018). CNN.

How Do You Choose the Best Reading Glasses Power? (March 2018). All About Vision.