What are refractive errors?

The cornea and lens of your eye bend (refract) light rays to focus them on the retina. Refractive errors happen when the shape of your eye prevents light from focusing correctly on the retina. This causes blurry vision. Changes in the eye's shape affect how light rays bend and focus, leading to vision problems.

What causes refractive errors?

Refractive errors can happen when:

• The eyeball is too long or too short.
• The cornea changes shape.
• The lens becomes less flexible as you age.

Each type of refractive error is different, but they all make it hard to see clearly.

What are common refractive errors?

Four common types of refractive errors include:

• Nearsightedness (myopia), blurred vision when looking at faraway objects.
• Farsightedness (hyperopia), blurred vision when looking at close-up objects.
• Astigmatism, blurred or distorted vision at all distances, which can make night vision harder.
• Presbyopia, difficulty seeing things up close because the lens becomes less flexible with age. It affects adults in middle age and older and often begins around age 45.

Who is at risk for refractive errors?

Anyone can have refractive errors. It's the most common type of vision problem. You may be more likely to have one if other family members wear glasses or contact lenses.

Most types of refractive errors start in childhood or are present at birth. Presbyopia is different. Nearly everyone develops it as they age, typically starting around age 45.

What are the symptoms of refractive errors?

Sometimes you may not notice vision changes right away, which is why regular eye exams are so important.

The most common symptom is blurred vision. Other symptoms may include:

• Double vision
• Haziness
• Glare or halos around bright lights
• A need to squint to see clearly
• Headaches
• Eye strain or tired eyes
• Difficulty focusing when reading or using a computer

If you already wear glasses or contact lenses and notice these symptoms, you may need a new prescription. Tell your eye care specialist if your vision changes or if you have problems with your glasses or contact lenses

How are refractive errors diagnosed?

An eye care specialist can diagnose refractive errors during a comprehensive eye exam. You'll be tested to see how well you can see at different distances, both with and without corrective lenses (glasses or contact lenses). Your provider may also use special eye drops to dilate (widen) your pupils to check for other eye conditions.

Different eye care specialists may be involved in your care. Here are some of the most common:

• Ophthalmologists are medical doctors who treat eye diseases, prescribe glasses or contact lenses, and perform eye surgery.
• Optometrists perform eye exams, diagnose vision problems, and prescribe glasses or contact lenses.
• Opticians fit or adjust glasses or contact lenses based on a prescription from your eye care specialist.

How are refractive errors treated?

Refractive errors are usually easy to correct with:

• Glasses
• Contact lenses
• Laser eye surgery, in some cases

Your eye care specialist can help choose the best treatment for your vision and lifestyle.

NIH: National Eye Institute