How Bad Is My Eye Prescription? Understanding The Numbers

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Medical News TodaySubscribeHow bad is my eye prescription? What the numbers mean

Medically reviewed by Vicente Diaz, MD, MBA — Written by Danielle Dresden — Updated on June 24, 2024

Understanding prescriptions
Changes
Improving vision
FAQ
Summary

Positive numbers on an eye prescription indicate they are correcting farsightedness, while negative numbers correct shortsightedness. A larger number suggests a stronger prescription.

Although roughly 3 out of every 4 people in America require corrective lenses, many people wonder how bad their eye prescription is – especially as the numbers and symbols are often difficult to interpret.

In this article, we look at how to read an eye prescription and what the numbers mean.

How to read an eye prescription

Eye exam equipment. — Gregory Adams/Getty Images

Positive numbers, such as +1.00, explain how strong a lens needs to be to correct for farsightedness. Farsightedness means a person can see distant things better than nearby objects.

Negative numbers, such as -1.00, indicate the lens strength needed to correct shortsightedness. Shortsightedness is when a person can see close things better than distant objects.

Other tips

The following tips can help people read their eye prescriptions:

A large number: Whether a + or -, a large number indicates a stronger prescription.
OS and OD: On an eyeglasses prescription, OS stands for Oculus Sinister, which refers to the left eye. OD stands for Oculus Dexter and refers to the right eye.
Eye differences: It is common for people to have different qualities of vision in their left and right eyes, particularly those with astigmatism.
Spherical correction (SPH): The spherical correction (SPH) refers to the lens strength needed to correct vision that affects the whole eye. This is usually the first number listed.
Cylindrical correction (CYL): Cylindrical correction is the second number and is only on prescriptions for people with astigmatism.
ADD: Some people need a different prescription to see things that are close by. ADD refers to the strength that the optician needs to add to a prescription to magnify objects.
AXIS: The axis notation tells lens makers where they should place the astigmatism correction in a lens.
PRISM: Eye doctors incorporate a prism into a lens to help correct problems with the eyes working together, such as one eye tilting inward while the other looks straight ahead.

A person with any questions about what their prescription means should speak to their optician who can answer any questions and help explain the numbers.

Why does my prescription change?

Eyeglass prescriptions change because people’s eyes change. Usually, these differences are not due to illness. For example, children do not fully develop the ability to focus both eyes on one object at the same time until they are seven years old.

Children’s eyes continue to change rapidly as they grow, and children who wear glasses should see an eye doctor each year to make sure their eyeglass prescriptions continue to meet their needs.

Adults’ eyes also change, although more slowly.

Although not all older adults will have eye problems, several eye conditions have associations with age, including:

Cataracts: The National Institutes of Health (NIH) expect over 50% of people in America to develop cataracts by age 75.
Glaucoma: If left untreated, glaucoma can cause vision loss and blindness.
Age-related macular degeneration: According to the NIH, this condition is the leading cause of blindness in people over 65.

The most common age-related change is presbyopia. More than one-third of Americans experience this condition, which develops as the aging eye lens becomes less flexible and stiffer. People can start developing presbyopia when they are in their 20’s.

As people age, the muscles that control the size of their pupils become weaker, which makes it more difficult for the eyes to adjust to changes in light.

The pupils generally become smaller, which makes it more difficult for a person to see in low-light conditions, such as driving at night.

Protecting and improving vision

People can take steps to protect and enhance their vision. Key recommendations from the National Eye Institute include:

getting a dilated eye exam
adopting a healthy lifestyle, including being physically active, eating a varied diet, and not smoking
protecting the eyes by using contacts carefully, wearing sunglasses and protective eyewear when needed, and taking breaks from computer screens

According to the Centers for Disease Control and Prevention (CDC), 93 million adults in the United States face a high risk of vision loss, but only half of them have seen an eye doctor in the past year.

Regular, thorough eye exams play a crucial role in maintaining and improving vision because they can catch potential eye problems early. According to the American Academy of Ophthalmology, a complete eye exam should include:

dilating the pupils to permit a thorough examination of the eye
reviewing medical history
testing pupil health
performing a visual acuity test to determine an individualized prescription
performing a peripheral vision test
carrying out an eye pressure check, or tonometry
checking the retina and optic nerve
reviewing eye movement, also known as ocular motility, plus eye alignment and eye muscle health
checking lens, cornea, iris, and eyelid

People with the following conditions need to pay special attention to protect the health of their eyes:

diabetes — damage to the retina because of high blood sugar is one of the most preventable causes of vision loss
high blood pressure
a family history of eye problems

Anyone who notices changes in their vision should speak to a medical professional to ensure early diagnosis and treatment.

Frequently asked questions

What does a +0.25 eye prescription mean?

A +0.25 eye prescription indicates a person has mild farsightedness (hyperopia), meaning they have a slight difficulty seeing objects up close.

Is 1.75 eyesight bad?

A 1.75 prescription, whether -1.75 (shortsightedness) or +1.75 (farsightedness), indicates moderate vision impairment.

Shortsightedness is when a person can see close things more easily than distant objects, while farsightedness is when a person can see distant things better than nearby objects.

Is minus 6.5 eyesight bad?

A -6.5 prescription indicates significant shortsightedness, meaning distant objects are very blurry. Eyeglasses or contact lenses are easy, common ways to correct shortsightedness.

Summary

Anyone wondering how bad their eye prescription is can look at the numbers and notes on their prescription and interpret them using the above guide.

People who want further details or guidance can speak to a medical professional, such as an optician, for a detailed explanation.

People need to take care of their general health and have regular eye exams to protect their vision. Most eye changes and resulting revisions of prescriptions are due to the expected effects of aging.

Eye Health / Blindness
Seniors / Aging

How we reviewed this article:

SourcesMedical News Today has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Buying prescription glasses or contact lenses: Your rights. (2023).https://consumer.ftc.gov/articles/buying-prescription-glasses-or-contact-lenses-your-rights
How to read your eyeglass prescription. (2023).https://opto.ca/eye-health-library/how-read-your-eyeglass-prescription
Keep your eyes healthy. (2021).https://www.nei.nih.gov/learn-about-eye-health/healthy-vision/keep-your-eyes-healthy
Mukamal, R. (2023). 20 Things to know about children's eyes and vision.https://www.aao.org/eye-health/tips-prevention/tips-children-eyes-vision
Mukamal, R. (2022). Could eyedrops replace reading glasses?https://www.aao.org/eye-health/news/could-eyedrops-replace-glasses-presbyopia
Normal vision development in children. (2020).https://www.aao.org/eye-health/tips-prevention/children-vision-development
Porter D. How to read an eyeglasses prescription. (2023).https://www.aao.org/eye-health/glasses-contacts/how-to-read-eyeglasses-prescription
Turbert, D. (2022). Eye exam and vision testing basics.https://www.aao.org/eye-health/tips-prevention/eye-exams-101
Turbert D. (2023). Nearsightedness: What is myopia?https://www.aao.org/eye-health/diseases/myopia-nearsightedness
Vision and eye health. (n.d.).https://www.cdc.gov/vision-health/index.html
Your aging eyes. How you see as time goes by. (2017).https://newsinhealth.nih.gov/special-issues/seniors/your-aging-eyes

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Medically reviewed by Vicente Diaz, MD, MBA — Written by Danielle Dresden — Updated on June 24, 2024

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Tag » What Is Considered Bad Eyesight

How Bad Is My Eye Prescription? Understanding The Numbers

How to read an eye prescription

Other tips

Why does my prescription change?

Protecting and improving vision

Frequently asked questions

What does a +0.25 eye prescription mean?

Is 1.75 eyesight bad?

Is minus 6.5 eyesight bad?

Summary

How we reviewed this article:

Latest news

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