On this page

Basics

• Summary
• Start Here
• Diagnosis and Tests
• Prevention and Risk Factors
• Treatments and Therapies

Learn More

• Related Issues
• Specifics
• Genetics

See, Play and Learn

• Images

Research

• Statistics and Research
• Clinical Trials
• Journal Articles

Resources

• Reference Desk
• Find an Expert

For You

• Children
• Patient Handouts

Summary

The cornea and lens of your eye helps you focus. Refractive errors are vision problems that happen when the shape of the eye keeps you from focusing well. The cause could be the length of the eyeball (longer or shorter), changes in the shape of the cornea, or aging of the lens.

Four common refractive errors are:

• Myopia, or nearsightedness - clear vision close up but blurry in the distance
• Hyperopia, or farsightedness - clear vision in the distance but blurry close up
• Presbyopia - inability to focus close up as a result of aging
• Astigmatism - focus problems caused by the cornea

The most common symptom is blurred vision. Other symptoms may include double vision, haziness, glare or halos around bright lights, squinting, headaches, or eye strain.

Glasses or contact lenses can usually correct refractive errors. Laser eye surgery may also be a possibility.

NIH: National Eye Institute

Start Here

• Astigmatism (National Eye Institute) Also in Spanish
• Refractive Errors (National Eye Institute) Also in Spanish
• Types of Refractive Errors (National Eye Institute)

Diagnosis and Tests

• Eye Exam and Vision Testing Basics (American Academy of Ophthalmology) Also in Spanish
• Retinoscopy (American Association for Pediatric Ophthalmology and Strabismus)
• Vision Screening (National Library of Medicine) Also in Spanish
• What Are Dilating Eye Drops? (American Association for Pediatric Ophthalmology and Strabismus)

Prevention and Risk Factors

• Get a Dilated Eye Exam (National Eye Institute) Also in Spanish

Treatments and Therapies

• Cornea Transplant (Mayo Foundation for Medical Education and Research)
• Eye Wear: MedlinePlus Health Topic (National Library of Medicine) Also in Spanish
• Laser Eye Surgery: MedlinePlus Health Topic (National Library of Medicine) Also in Spanish
• Phakic Intraocular Lenses (Food and Drug Administration)
• What Is Refractive Surgery? (American Academy of Ophthalmology) Also in Spanish

Related Issues

• Abnormal Head Position (American Association for Pediatric Ophthalmology and Strabismus)
• What Are the Risks and How Can I Find the Right Doctor for Me? (Refractive Surgery) (Food and Drug Administration)

Specifics

• Astigmatism (Mayo Foundation for Medical Education and Research)
• Corneal Conditions (National Eye Institute)
• Presbyopia (Mayo Foundation for Medical Education and Research)
• Progressive (High) Myopia (American Association for Pediatric Ophthalmology and Strabismus)

Genetics

• Deafness and myopia syndrome: MedlinePlus Genetics (National Library of Medicine)
• Farsightedness: MedlinePlus Genetics (National Library of Medicine)
• Nearsightedness: MedlinePlus Genetics (National Library of Medicine)

Images

• Corneal transplant - series (Medical Encyclopedia) Also in Spanish

Statistics and Research

• Eye Health Data and Statistics (National Eye Institute) Also in Spanish

Clinical Trials

• ClinicalTrials.gov: Astigmatism (National Institutes of Health)
• ClinicalTrials.gov: Hyperopia (National Institutes of Health)
• ClinicalTrials.gov: Lenses, Intraocular (National Institutes of Health)
• ClinicalTrials.gov: Myopia (National Institutes of Health)
• ClinicalTrials.gov: Presbyopia (National Institutes of Health)
• ClinicalTrials.gov: Refractive Errors (National Institutes of Health)

Journal Articles References and abstracts from MEDLINE/PubMed (National Library of Medicine)

• Article: Impact of Genetic and Environmental Factors on Peripheral Refraction.
• Article: Prevalence and association of uncorrected refractive error among Chinese adolescents: a...
• Article: Refractive error and ocular alignment in school-aged children from low-income areas...
• Refractive Errors -- see more articles

Reference Desk

• How the Eyes Work (National Eye Institute) Also in Spanish

Find an Expert

• American Optometric Association
• Find a Doctor of Optometry (American Optometric Association)
• Find an Ophthalmologist (American Academy of Ophthalmology) Also in Spanish
• Finding an Eye Doctor (National Eye Institute)
• National Eye Institute

Children

• Anisometropia (American Association for Pediatric Ophthalmology and Strabismus)
• Farsightedness (Hyperopia) (For Parents) (Nemours Foundation)
• Nearsightedness (Myopia) (For Parents) (Nemours Foundation) Also in Spanish
• Photoscreening (American Association for Pediatric Ophthalmology and Strabismus)
• Refractive Errors in Children (American Association for Pediatric Ophthalmology and Strabismus)
• Treatment of Increasing Myopia in Children (American Association for Pediatric Ophthalmology and Strabismus)
• Your Child's Vision (Nemours Foundation) Also in Spanish

Patient Handouts

• Astigmatism (Medical Encyclopedia) Also in Spanish
• Farsightedness (Medical Encyclopedia) Also in Spanish
• Nearsightedness (Medical Encyclopedia) Also in Spanish
• Presbyopia (Medical Encyclopedia) Also in Spanish
• Refraction (Medical Encyclopedia) Also in Spanish