Definition Refractive Error
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Errors Refractive Errors Reviewed by Jill E. Bixler, M.D. On this page: What Is refractive error in children a Refractive Error? Symptoms Causes Risk Factors Tests and Diagnosis Treatment and Drugs Clinic Information What Is a Refractive Error? Refractive
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error means 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 refractive error correction surgery age), and astigmatism. Symptoms Blurred vision Difficulty reading or seeing up close Crossing of the eyes in children (esotropia) Causes Overuse 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 refractive error hypermetropia 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 close range. This normal aging process of the lens can also be combined with myopia, hyperopia or astigmatism. Watch a video explaining presbyopia. Astigmatism Astigmatism usually occurs when the front surface of the eye, the cornea, has an asymmetric curvature. Normally the cornea is smooth and equally curved in all directions, and light entering the cornea is focused equally on all planes, or in all directions. In astigmatism, the front surface of the cornea is curved more in one direction than in another. This abnormality may result in vision that is much like looking into a distorted, wavy mirror. Usually, astigmatism
中文 English Français Русский Español RSS Feed Youtube Twitter Facebook Google + iTunes Play Store What is a refractive error? Online Q&A 7 October 2013 Q: What is a refractive error? A: A refractive error is a very common
Refractive Error Astigmatism
eye disorder. It occurs when the eye cannot clearly focus the images from the refractive error pdf outside world. The result of refractive errors is blurred vision, which is sometimes so severe that it causes visual impairment. The
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four most common refractive errors are: myopia (nearsightedness): difficulty in seeing distant objects clearly; hyperopia (farsightedness): difficulty in seeing close objects clearly; astigmatism: distorted vision resulting from an irregularly curved cornea, the clear covering of the http://kellogg.umich.edu/patientcare/conditions/refractive.errors.html eyeball. presbyopia: which leads to difficulty in reading or seeing at arm's length, it is linked to ageing and occurs almost universally. Refractive errors cannot be prevented, but they can be diagnosed by an eye examination and treated with corrective glasses, contact lenses or refractive surgery. If corrected in time and by eye-care professionals, they do not impede the full development of good visual function. Correction is provided in different forms according http://www.who.int/features/qa/45/en/ to the defect, the age f the person, the requirements in terms of work of activity performed. WHO estimates that 153 million people worldwide live with visual impairment due to uncorrected refractive errors. This figure does not include the people living with uncorrected presbyopia, which is likely to be quite significant, according to some early evidence. WHO, its Member States and partners are working to find ways to provide good quality, professionally prescribed, local, affordable corrective refraction services to people in need, especially in poor areas with limited eye care services. Related links Refractive errors and low vision Prevention of avoidable blindness and visual impairment Share Email Twitter Facebook Google Delicious LinkedIn More... Print Question and answer archives Submit a question You are here: Features Online Q&A Quick Links Sitemap Home Health topics Data Media centre Publications Countries Programmes and projects Governance About WHO Help and Services Contacts FAQs Employment Feedback Privacy E-mail scams WHO Regional Offices WHO African Region WHO Region of the Americas WHO South-East Asia Region WHO European Region WHO Eastern Mediterranean Region WHO Western Pacific Region RSS Feeds WHO YouTube channel Follow WHO on Twitter WHO Facebook page WHO Google+ page WHO iTunes WHO Play Store © WHO 2016 Back to top Email Address Sign up for WHO updates
often are the main reason a person seeks the services of an optometrist or ophthalmologist. But what does it really mean when we're told that our http://www.allaboutvision.com/eye-exam/refraction.htm vision is blurry because we have a refractive error? We see the world around us because of the way our eyes bend (refract) light. Refractive errors are optical imperfections that prevent the http://www.sankaranethralaya.org/lasik-refractive-errors.html eye from properly focusing light, causing blurred vision. The primary refractive errors are nearsightedness, farsightedness and astigmatism. Refractive errors usually can be "corrected" with eyeglasses or contact lenses, or they can be refractive error permanently treated with LASIK and other vision correction surgery (also called refractive surgery). FIND A DOCTOR: Do you have a refractive error? Find an eye doctor near you to have your eyes checked. > How Light Travels Through the Eye In order to see, we must have light. While we don't fully understand all the different properties of light, we do have an idea of definition refractive error how light travels. Watch this video on what causes blurry vision and how we can correct it. A light ray can be deflected, reflected, bent or absorbed, depending on the different substances it encounters. When light travels through water or a lens, for example, its path is bent or refracted. Certain eye structures have refractive properties similar to water or lenses and can bend light rays into a precise point of focus essential for sharp vision. Most refraction in the eye occurs when light rays travel through the curved, clear front surface of the eye (cornea). The eye's natural (crystalline) lens also bends light rays. Even the eye's tear film and internal fluids (aqueous humor and vitreous) have refractive abilities. Recommended For You Pay for your family's vision care with a CareCredit credit card Learn how Optometry Giving Sight helps 670 million people to see again Questions about cataracts? Find all the answers in My Cataract Journey Save 10-30% off your eye exam using the BenefitsPal™ card How the Eye Sees The process of vision begins when light rays that reflect off objects and travel through the eye's optical system are refracted
Instructions Laser Vision Correction LASIK Technology LASIK Testimonials Online Appointment LASIK Downloads Corneal surgery handbook LASIK Follow-Up Form LASIK@SN Back to LASIK Main Page LASIK CORNER What is Refractive Error? Normally, the rays of light entering the eye are brought to a precise focus on the retina – the light sensitive layer lining the back of the eye. When such a focus is not achieved, a refractive error results and vision is not clear. These imperfections in the focusing power of the eye are called refractive errors. The common refractive errors are: Myopia, or Nearsightedness; Hyperopia, or Farsightedness; Astigmatism Myopia: A myopic eye is longer than normal or has a cornea that is too steep, as a result of which the light rays focus in front of the retina. Close objects look clear, but distant objects appear blurred. Hyperopia (Farsightedness): Hyperopia is a term used to describe the condition of farsightedness. The causes of hyperopia are typically genetic and involve an eye that is too short or a cornea that is too flat, as a result of which images focus at a point behind the Retina. People with hyperopia can usually see distant objects well, but have trouble focussing on nearby objects Astigmatism (Distorted vision): courtesy : Allergan ; Eye Calender ASTIGMATISM (cylindrical error) occurs when the incoming light rays are unable to reach a common focus within the eye. Astigmatism distorts or blurs vision for both near and far objects. The cornea is the clear front window of the eye. A normal cornea is round and smooth, like a basketball. When you have astigmatism, the cornea curves more in one direction than in the other, like a football. It is possible to have astigmatism in combination with myopia or hyperopia. Our Websites Support Sankara Nethralaya Home Ophthalmic Links SN Kolkata SN Omtrust About Us LASIK International Patient Services Omlog Patient Care Feed Back Vision & Mission Statement The Sankara Nethralaya Academy Ed