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Refractive Errors
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Eyes Vision

Refractive Errors

Refractive errors occur when the shape of the eye prevents light from focusing correctly on the retina, resulting in blurred vision.

Causes

The cornea and lens of the eye bend (refract) light rays to focus them on the retina. Refractive errors can occur when:

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

Common Types

  • 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. This typically begins around age 45.

Risk Factors

Refractive errors are the most common type of vision problem. You may be more likely to have one if family members wear glasses or contact lenses. While most types start in childhood or are present at birth, presbyopia affects nearly everyone as they age.

Symptoms

The most common symptom is blurred vision. Other signs 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

Diagnosis

An eye care specialist can diagnose these errors during a comprehensive eye exam. You will be tested on how well you see at different distances, both with and without corrective lenses. Providers may also use eye drops to dilate the pupils to check for other conditions.

Specialists involved in your care may include:

  • Ophthalmologists: Medical doctors who treat eye diseases, prescribe corrective lenses, and perform surgery.
  • Optometrists: Professionals who perform eye exams, diagnose vision problems, and prescribe corrective lenses.
  • Opticians: Professionals who fit or adjust glasses or contact lenses based on a prescription.

Treatment

Refractive errors are usually easy to correct with:

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

Frequently Asked Questions

Squinting narrows the aperture of the eye, which reduces the amount of light entering and can create a pinhole effect that sharpens the image on the retina by minimizing the blur circle caused by refractive errors. While it provides temporary clarity, it does not correct the underlying shape issue of the eye and can lead to eye strain and headaches. If you find yourself squinting frequently to see distant or close objects, it is a strong indicator that you have an uncorrected refractive error such as myopia, hyperopia, or astigmatism that requires prescription lenses.
For most people, refractive errors stabilize in their late teens or early twenties. However, myopia can continue to progress slowly in some adults, particularly if there is a genetic predisposition or high levels of near-work. Astigmatism can also change due to corneal shape alterations from conditions like keratoconus or changes in eye pressure. If you notice a sudden change in your prescription or increased blurriness in adulthood, it is important to get a comprehensive eye exam to rule out other underlying eye diseases that may be mimicking a simple refractive shift.
Farsightedness (hyperopia) is a refractive error where the eyeball is too short or the cornea is too flat, causing light to focus behind the retina, which can affect both near and far vision. Presbyopia is an age-related condition where the lens loses its flexibility, making it difficult to focus on close objects regardless of your existing refractive status. Most people begin to notice presbyopia around age 45 because the natural lens hardens over time, reducing its ability to change shape for near focus, which is why reading glasses become necessary even if your distance vision was previously perfect.
Refractive errors typically cause consistent blurriness at specific distances that can be corrected with lenses. If your vision is blurry but you also experience symptoms like floaters, flashes of light, a curtain over your vision, double vision, or eye pain, it is not a simple refractive error and requires immediate medical attention. These symptoms can indicate retinal detachment, glaucoma, or optic nerve issues. A comprehensive dilated eye exam is the only way to definitively distinguish between a need for new glasses and a potential pathological condition.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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