Ophthalmology Refractive Error
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this page: What Is a Refractive Error? Symptoms Causes Risk Factors Tests and Diagnosis Treatment and Drugs Clinic Information What Is a Refractive Error? Refractive error means types refractive errors that the shape of your eye does not bend light correctly, resulting in a blurred image. The main types of refractive errors are myopia (nearsightedness), hyperopia (farsightedness), presbyopia (loss of near vision with age), and astigmatism. Symptoms Blurred vision Difficulty reading or seeing up close Crossing of the eyes in children (esotropia) Causes Overuse refractive error treatment of the eyes does not cause or worsen refractive error. The causes of the main types of refractive error are described below: Myopia(close objects are clear, and distant objects are blurry) Also known as nearsightedness, myopia is usually inherited and often discovered in childhood. Myopia often progresses throughout the teenage years when the body is growing rapidly. Watch a video explaining myopia. Hyperopia (close objects are more blurry than distant objects) Also known as farsightedness, hyperopia can also be inherited. Children often have hyperopia, which may lessen in adulthood. In mild hyperopia, distance vision is clear while near vision is blurry. In more advanced hyperopia, vision can be blurred at all distances. Watch a video explaining hyperopia. Presbyopia (aging of the lens in the eye) After age 40, the lens of the eye becomes more rigid and does not flex as easily. As a result, the eye loses its focusing ability and it becomes more difficult to read at
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of the Scientific Director Office of the Clinical Director Education Programs All Education National Eye Health Education Program Diabetic Eye Disease Education Program Glaucoma Education Program Low Vision Education Program Spanish-language Education Program (¡Ojo http://kellogg.umich.edu/patientcare/conditions/refractive.errors.html con su visión!) Vision and Aging Program Training and Jobs All Training and Jobs NEI Summer Intern Program Diversity In Vision Research & Ophthalmology (DIVRO) Student Training Programs NEI Home About NEI Health Information News and Events Grants and Funding Research at NEI Education Programs Training and Jobs Home > Eye Health Information > Refractive Errors > Facts About Refractive Errors Facts About Refractive Errors https://nei.nih.gov/health/errors/errors This information was developed by the National Eye Institute to help patients and their families search for general information about refractive errors. An eye care professional who has examined the patient’s eyes and is familiar with his or her medical history is the best person to answer specific questions. Refractive Errors Defined What are refractive errors? Refractive errors occur when the shape of the eye prevents light from focusing directly on the retina. The length of the eyeball (longer or shorter), changes in the shape of the cornea, or aging of the lens can cause refractive errors. What is refraction? Refraction is the bending of light as it passes through one object to another. Vision occurs when light rays are bent (refracted) as they pass through the cornea and the lens. The light is then focused on the retina. The retina converts the light-rays into messages that are sent through the optic nerve to the brain. The brain interprets these messages into the images we see. Frequently Asked Questions about Refractive Errors What are the different types of refractive errors? The most common types of refractive errors are myopia, hyperopia, presbyopia, and astigmatism. Myopia (nearsightedness) is a condition where objects up close appear clearly, while objects far away appear blurry. With myopia, light com
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Asked Questions Español Condiciones Chinese Conditions Refractive Errors in Children En Español Read in Chinese How does the eye focus light? In order to see clearly, light rays from an object must focus onto the inner back layer of the eye [See figure 1]. The eye works like a camera. It has an opening at the front (the pupil), a focusing mechanism (the cornea and crystalline lens), and a light-sensing portion at the back (the retina). If light rays are not focused on the retina, a refractive error is present. The refractive errors are: myopia, hyperopia and astigmatism [See figures 2 and 3]. What is hyperopia (farsightedness)? Hyperopia occurs when light rays focus behind the retina (because the eye is either too short or has too little focusing power) and causes near and distant objects to appear blurry. The signs and symptoms of farsightedness are more severe the closer the object of regard. Some hyperopia is normal in childhood and correction is typically not required. Children can compensate for this on their own using their natural focusingmechanism (accommodation). A large amount of hyperopia may require correction with converging or plus (+) power glasses, particularly when associated with crossed eyes (accommodative esotropia). Hyperopia usually increases in early childhood and then decreases during preteen to early teenage years. Contact lenses and laser surgery are alternatives to spectacles at the appropriate age. What is myopia (nearsightedness)? Myopia occurs when light rays focus in front of the retina because the eye is too long or has excessive focusing power. Objects in the distance appear blurry and as they get closer to the eye, are seen more clearly. This condition may be inherited or associated with premature birth and can occur at any age. The prevalence of myopia is low in US children under the age of eight, but much higher in Asian countries. Diverging or minus (-) power glasses focus the light rays on the retina and improve vision. Myopia usually progresses yearly and stabilizes by the late teens to early twenties. There is currently no widely accepted treatment to stop progression. Some recent epidemiological data suggests that more time spent outdoors was associated with less myopic progression. There is no spec