Difference between revisions of "Hyperopia" - New World Encyclopedia
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| − | '''Hyperopia''' or '''hypermetropia''', | + | '''Hyperopia''' or '''hypermetropia''', commonly known as '''farsightedness''' or '''longsightedness,''' is an abnormal eye condition whereby there is better visual acuity for objects in the distance than nearby objects. This results when when incoming light rays enter the eye and converge behind the [[retina]] to create a blurred object, instead of converging directly on the retina to create a focused object. |
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| + | This defect can be attributed to the length of the [[eye]], if it is too short from front to back, or to the roundness of the [[Lens (anatomy)|lens]], if it is not round enough. Both cause incoming light rays to pass through the retina before converging and thus the inability to [[Focus (optics)|focus]] on near objects. An extreme case of this defect of [[visual system|vision]] is the incapability to focus on objects at any [[distance]]. As an object moves towards the eye, the eye must increase its power to keep the image on the [[retina]]. If the power of the cornea and lens is insufficient, the image will appear blurred. | ||
[[Image:Hypermetropia.svg|thumb|250 px|right|Hyperopia, and restoring of vision with convex lens]] | [[Image:Hypermetropia.svg|thumb|250 px|right|Hyperopia, and restoring of vision with convex lens]] | ||
| + | ==Overview== | ||
| + | The lens system of the eye is designed so that incoming, parallel light rays are bent to converge at a point behind the lens, ideally on the retina for perfect vision.<ref name="Longe2005">B. Rowland and T. G. Odle, "Hyperopia," in J. L. Longe, ''The Gale Encyclopedia of Alternative Medicine'' (Farmington Hills, Mich: Thomson/Gale, 2005). ISBN 0787693960.</ref> In hyperopia, the point of focus of light rays coming from an object occurs behind the retina.<ref name="Longe2005"> | ||
| − | People with hyperopia can experience [[defocus aberration|blurred vision]], [[asthenopia]] or fatigue of the eye, and [[accommodation (eye)|accommodative dysfunction]] or the inability of the eye lens to reshape in order to focus on near objects. | + | People with hyperopia can experience [[defocus aberration|blurred vision]], [[asthenopia]], or fatigue of the eye, and [[accommodation (eye)|accommodative dysfunction]] or the inability of the eye lens to reshape in order to focus on near objects. In addition, a person may experience [[binocular vision|binocular dysfunction]], [[amblyopia]] (better known as lazy eye), or even [[strabismus]], where the eyes are misaligned and cannot focus on the same object at the same time, similar to cross-eyed.<ref name="AOA Hyperopia">American Optometric Association. ''[http://www.aoa.org/documents/CPG-16.pdf Optometric Clinical Practice Guideline: Care of the patient with hyperopia.]'' 1997.</ref> |
| − | + | Hyperopia is often confused with [[presbyopia]],<ref name="WebMD">Cleveland Clinic and C. D. Haines. 2005. [http://www.webmd.com/content/article/63/72009 Eye health: Presbyopia and your eyes.] ''WebMD''. Retrieved September 21, 2006.</ref><ref>B. Chou. n.d. [http://www.refractivesource.com/patients/ref_error_pres.htm "Refractive Error and Presbyopia."] ''Refractive Source''. Retrieved September 20, 2006.</ref>, another condition that frequently causes blurry near vision.<ref name="AOA Presbyopia">American Optometric Association. 1998. [http://www.aoa.org/documents/CPG-17.pdf Optometric clinical practice guideline: Care of the patient with presbyopia.]. ''American Optometric Association''. Retrieved October 28, 2007. </ref> Presbyopia is a natural age-related process which causes people in their mid-40's to experience vision problems, namely to close objects. This occurs because the lens begins to harden and become less flexible to adjust to focus objects up close, which is different from the cause of hyperopia, which is due to the shape of the eye. Like hyperopia, presbyopia also is sometimes referred to as farsightedness, since in otherwise normally-sighted persons it makes it more difficult to focus on near objects than on far objects.<ref>K. Tsubota, B. S. Boxer Wacher, D. T. Azar, and D. D. Koch, eds., 2003. ''Hyperopia and Presbyopia''. New York: Marcel Decker</ref>. | |
| − | Hyperopia is often confused with [[presbyopia]] <ref name="WebMD">[http://www.webmd.com/content/article/63/72009 | ||
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| − | </ref><ref>Chou | ||
==Causes and Symptoms of hyperopia== | ==Causes and Symptoms of hyperopia== | ||
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==External links== | ==External links== | ||
Revision as of 22:54, 29 October 2007
| [[Image:{{{Image}}}|190px|center|]] | |
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| ICD-10 | H52.0 |
| ICD-O: | {{{ICDO}}} |
| ICD-9 | 367.0 |
| OMIM | {{{OMIM}}} |
| MedlinePlus | {{{MedlinePlus}}} |
| eMedicine | {{{eMedicineSubj}}}/{{{eMedicineTopic}}} |
| DiseasesDB | {{{DiseasesDB}}} |
Hyperopia or hypermetropia, commonly known as farsightedness or longsightedness, is an abnormal eye condition whereby there is better visual acuity for objects in the distance than nearby objects. This results when when incoming light rays enter the eye and converge behind the retina to create a blurred object, instead of converging directly on the retina to create a focused object.
This defect can be attributed to the length of the eye, if it is too short from front to back, or to the roundness of the lens, if it is not round enough. Both cause incoming light rays to pass through the retina before converging and thus the inability to focus on near objects. An extreme case of this defect of vision is the incapability to focus on objects at any distance. As an object moves towards the eye, the eye must increase its power to keep the image on the retina. If the power of the cornea and lens is insufficient, the image will appear blurred.
Overview
The lens system of the eye is designed so that incoming, parallel light rays are bent to converge at a point behind the lens, ideally on the retina for perfect vision.[1] In hyperopia, the point of focus of light rays coming from an object occurs behind the retina.Cite error: Closing </ref> missing for <ref> tag
Hyperopia is often confused with presbyopia,[2][3], another condition that frequently causes blurry near vision.[4] Presbyopia is a natural age-related process which causes people in their mid-40's to experience vision problems, namely to close objects. This occurs because the lens begins to harden and become less flexible to adjust to focus objects up close, which is different from the cause of hyperopia, which is due to the shape of the eye. Like hyperopia, presbyopia also is sometimes referred to as farsightedness, since in otherwise normally-sighted persons it makes it more difficult to focus on near objects than on far objects.[5].
Causes and Symptoms of hyperopia
Hyperopia can be due to family history, and in some cases, can be outgrown due to the changing lens shape throughout the adolescent years (Hyperopia). In extreme cases, diseases such as retinopathy, a nonimflammatory retina disorder, can also help cause hyperopia [6]. Other examples include eye tumors and lens dislocation which may also attribute to hyperopia.
Depending on the severity of hyperopia, an individual may experience a great number of symptoms to none at all. In extreme cases, close up and distant vision is impaired, where all objects are blurry. Other times objects are only out of focus for close by objects. Headaches, aching eyes, burning and eyestrain are the most common symptoms, especially when looking at objects up close. Children do not usually experience many symptoms. However, if a child continuously rubs his or her eyes, becomes cross-eyed or has estropia (one eye points inward), or loses interest in reading, these could all be signs that the child may have hyperopia and should be examined by an ophthalmologist (Farsightedness-Hyperopia).
Other signs of hyperopia include tearing, redness in the eye, squinting, facial contortions, rapid blinking, and decreased hand-eye coordination.[7]
Classification of hyperopia
Hyperopia is typically classified according to clinical appearance, its severity, or how it relates to the eye's accommodative status.[7]
Classification by clinical appearance
- Simple hyperopia- from normal biological variation
- Pathological hyperopia- from maldevelopment or ocular disease
- Functional hyperopia- from paralysis of accommodation.[7]
Diagnosis
Detection through normal eye exams or photoscreening is usually the best method of detecting hyperopia. Visual acuity is affected according to the amount of hyperopia, as well as the patient's age, visual demands, and accommodative ability.[7]. In addition, static retinoscopy, subjective refraction and autorefraction are procedures to measure refractive error.
Prevention and Treatment
Causes of hyperopia are usually found in early childhood and in most cases a person outgrows such defects through normal adulthood development and lengthening of the eyeball, therefore treatment depends heavily on the age of the patient (Farsightedness).
Various eye care professionals, including ophthalmologists, optometrists, orthoptists, and opticians, are involved in the treatment and management of hyperopia. Minor cases of hyperopia are sometimes left uncorrected, however, larger amounts may be corrected with convex lenses in eyeglasses or contact lenses. Convex lenses have a positive dioptric value, which causes the light to focus closer than its normal range. For very severe cases, options such as laser surgery (H-LASIK), photorefractive keratectomy (H-PRK), or intraocular lens implants (IOLs) exist (Farsightedness). Hyperopia is sometimes correctable with various refractive surgery procedures.
Simple lifestyle changes can help ease common symptoms such as creating an environment with better lighting, reducing glare, and even taking care of visual hygiene. In some aspects, pharmaceutical treatments such as anticholinesterase agents can be prescribed.[7]
Notes
- ↑ B. Rowland and T. G. Odle, "Hyperopia," in J. L. Longe, The Gale Encyclopedia of Alternative Medicine (Farmington Hills, Mich: Thomson/Gale, 2005). ISBN 0787693960.
- ↑ Cleveland Clinic and C. D. Haines. 2005. Eye health: Presbyopia and your eyes. WebMD. Retrieved September 21, 2006.
- ↑ B. Chou. n.d. "Refractive Error and Presbyopia." Refractive Source. Retrieved September 20, 2006.
- ↑ American Optometric Association. 1998. Optometric clinical practice guideline: Care of the patient with presbyopia.. American Optometric Association. Retrieved October 28, 2007.
- ↑ K. Tsubota, B. S. Boxer Wacher, D. T. Azar, and D. D. Koch, eds., 2003. Hyperopia and Presbyopia. New York: Marcel Decker
- ↑ [Dictionary.com. Merriam-Webster's Medical Dictionary. Merriam-Webster, Inc. http://dictionary.reference.com/browse/retinopathy (accessed: October 06, 2007)]
- ↑ 7.0 7.1 7.2 7.3 7.4 Cite error: Invalid
<ref>tag; no text was provided for refs namedAOA Hyperopia
External links
- pupilEyes - Learn how Hyperopia happens
- DocShop.com - Hyperopia Treatments
- Scottish Sensory Centre - Medical Info on Hypermetropia
- Presbyopia
- Farsightedness
- [1]- Hyperopia
- Farsightedness-Hyperopia
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