MedlinePlus is a service of the National Library of Medicine (NLM), the world's largest medical library, which is part of the National Institutes of Health (NIH). It was built as an online health information resource for patients and their families and friends.
MedlinePlus presents high-quality, easy to understand, relevant health and wellness information that is trusted.
MedlinePlus at a Glance
- Offers information on health topics, human genetics, medical tests, medications, dietary supplements, and healthy recipes.
- Sourced from more than 1,600 selected organizations.
- Provides 40,000 links to authoritative health information in English and 18,000 links to information in Spanish.
- In 2018, 277 million users viewed MedlinePlus more than 700 million times.
Refractive Errors
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
