Myopia Classification and external resources
ICD-10	H52.1
ICD-9	367.1
DiseasesDB	8729
MeSH	D009216

Myopia (from Greek: μυωπία myopia "near-sightedness"^[1]), also called near- or short-sightedness, is a refractive defect of the eye in which collimated light produces image focus in front of the retina when accommodation is relaxed. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly A refractive error, or refraction error, is an error in the focusing of Light by the Eye and a frequent reason for reduced Visual acuity Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain Collimated light is Light whose rays are nearly parallel and therefore will spread slowly as it propagates In Geometrical optics, a focus, also called an image point, is the point where Light rays originating from a point on the object converge. The vertebrate retina is a light sensitive part inside the inner layer of the Eye. Accommodation is the process by which the:eye increases Optical power to maintain a clear image ( focus) on an object as it draws near the eye

Those with myopia see nearby objects clearly but distant objects appear blurred. In Psychology, visual perception is the ability to interpret information from Visible light reaching the Eyes The resulting Perception is also In Geometrical optics, a focus, also called an image point, is the point where Light rays originating from a point on the object converge. With myopia, the eyeball is too long, or the cornea is too steep, so images are focused in the vitreous inside the eye rather than on the retina at the back of the eye. The cornea is the transparent front part of the Eye that covers the iris, Pupil, and Anterior chamber. The vertebrate retina is a light sensitive part inside the inner layer of the Eye. The opposite defect of myopia is hyperopia or "farsightedness" or "long-sightedness" — this is where the cornea is too flat or the eye is too short. Hyperopia, also known as farsightedness or longsightedness, is a Defect of vision caused by an imperfection in the Eye (often when

Mainstream ophthalmologists and optometrists most commonly correct myopia through the use of corrective lenses, such as glasses or contact lenses. Ophthalmology is the branch of Medicine which deals with the diseases and surgery of the visual pathways including the Eye, Brain Optometry is a health care profession concerned with Eyes and related structures as well as vision, Visual systems and vision information A corrective lens is a lens worn in front of the Eye, mainly used to treat Myopia, Hyperopia, astigmatism, and adjustable focus Glasses, also called eyeglasses or spectacles, are frames bearing lenses worn in front of the Eyes normally for vision correction, A contact lens (also known simply as a contact) is a corrective, cosmetic, or therapeutic lens usually placed on the Cornea It may also be corrected by refractive surgery, such as LASIK. Refractive eye surgery is any Eye surgery used to improve the refractive state of the Eye and decrease or eliminate dependency on Glasses or Contact LASIK or Lasik ( Laser -assisted In situ Keratomileusis) is a type The corrective lenses have a negative optical power (i. A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging Optical power ( dioptric power or refractive power) is the degree to which a lens or Mirror converges or diverges light e. are concave) which compensates for the excessive positive diopters of the myopic eye. In some cases, pinhole glasses are used by patients with low-level myopia. Pinhole glasses, also known as stenopeic glasses, are eyeglasses with a series of pinhole-sized perforations filling an opaque sheet of plastic in place of each lens These work by reducing the blur circle formed on the retina.

Contents 1 Classification 1.1 Etiology 1.2 Clinical entity 1.3 Degree 1.4 Age of onset 2 Epidemiology 2.1 Ethnicity and race 2.2 Education, intelligence, and IQ 3 Etiology and pathogenesis 3.1 Theories 3.2 Relevant research 4 Presbyopia and the 'payoff' for the nearsighted 5 Diagnosis 6 Treatment, management, and prevention 6.1 Eye-exercises and biofeedback 6.2 Prevention 6.3 Myopia control 7 Myopia as metaphor 8 See also 9 References 10 External links

Classification

Myopia has been classified in various manners. ^[2][3][4]

Etiology

Borish and Duke-Elder classified myopia by cause:^[3][4]

• Axial myopia is attributed to an increase in the eye's axial length. ^[5]
• Refractive myopia is attributed to the condition of the refractive elements of the eye. ^[5] Borish further subclassified refractive myopia:^[3]

• Curvature myopia is attributed to excessive, or increased, curvature of one or more of the refractive surfaces of the eye, especially the cornea. ^[5] In those with Cohen syndrome, myopia appears to result from high corneal and lenticular power. Cohen syndrome (also known as Pepper syndrome or Cervenka syndrome, named after Michael Cohen William Pepper and Jaroslav Cervenka who researched the illness is ^[6]
• Index myopia is attributed to variation in the index of refraction of one or more of the ocular media. The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium ^[5]

Clinical entity

Various forms of myopia have been described by their clinical appearance:^[4][7]

• Simple myopia is more common than other types of myopia and is characterized by an eye that is too long for its optical power (which is determined by the cornea and crystalline lens) or optically too powerful for its axial length. Optical power ( dioptric power or refractive power) is the degree to which a lens or Mirror converges or diverges light The cornea is the transparent front part of the Eye that covers the iris, Pupil, and Anterior chamber. The lens is a transparent biconvex structure in the Eye that along with the Cornea, helps to Refract Light to be focused ^[8] Both genetic and environmental factors, particularly significant amounts of near work, are thought to contribute to the development of simple myopia. ^[8]
• Degenerative myopia, also known as malignant, pathological, or progressive myopia, is characterized by marked fundus changes, such as posterior staphyloma, and associated with a high refractive error and subnormal visual acuity after correction. A staphyloma is an abnormal protrusion of the Uveal tissue through a weak point in the the Eyeball. ^[5] This form of myopia gets progressively worse over time. Degenerative myopia has been reported as one of the main causes of visual impairment. Visual impairment or vision impairment is Vision loss that constitutes a significant limitation of visual capability resulting from Disease, ^[9] Myopia with degenerative changes has been described as being very common in certain races and cultures, such as Chinese, Japanese, Korean, Arab, and Jewish people. ^[10]
• Nocturnal myopia, also known as night myopia or twilight myopia, is a condition in which the eye has a greater difficulty seeing in low illumination areas, even though its daytime vision is normal. Essentially, the eye's far point of an individual's focus varies with the level of light. Night myopia is believed to be caused by pupils dilating to let more light in, which adds aberrations resulting in becoming more nearsighted. A stronger prescription for myopic night drivers is often needed. Younger people are more likely to be affected by night myopia than the elderly. ^[11]
• Pseudomyopia is the blurring of distance vision brought about by spasm of the ciliary muscle. Pseudomyopia refers to an intermittent and temporary shift in Refraction of the eye towards Myopia, in which the focusing of light in front of the retina is due to The Ciliary Muscle is a muscle in the eye that controls the eye's accommodation for viewing objects at varying distances ^[12]
• Induced myopia, also known as acquired myopia, results from exposure to various pharmaceuticals, increases in glucose levels, nuclear sclerosis, or other anomalous conditions. Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. Nuclear sclerosis is an age-related change in the Density of the crystalline lens nucleus that occurs in all older animals ^[8] The encircling bands used in the repair of retinal detachments may induce myopia by increasing the axial length of the eye. ^[13]

• Index myopia is attributed to variation in the index of refraction of one or more of the ocular media. ^[5] Cataracts may lead to index myopia. ^[14]
• Form deprivation myopia is a type of myopia that occurs when the eye is deprived of clear form vision. ^[15] Myopia is often induced this way in various animal models to study the pathogenesis and mechanism of myopia development. ^[15]

Degree

Myopia, which is measured in diopters by the strength or optical power of a corrective lens that focuses distant images on the retina, has also been classified by degree or severity:^[2]

• Low myopia usually describes myopia of −3. A dioptre, or diopter, is a Unit of measurement of the Optical power of a lens or curved Mirror, which is equal to the reciprocal Optical power ( dioptric power or refractive power) is the degree to which a lens or Mirror converges or diverges light 00 diopters or less. ^[5]
• Medium myopia usually describes myopia between −3. 00 and −6. 00 diopters. A dioptre, or diopter, is a Unit of measurement of the Optical power of a lens or curved Mirror, which is equal to the reciprocal ^[5] Those with moderate amounts of myopia are more likely to have pigment dispersion syndrome or pigmentary glaucoma. Pigment dispersion syndrome (PDS is an affliction of the Eye that if left untreated can lead a form of Glaucoma known as pigmentary glaucoma. Glaucoma is a group of diseases of the Optic nerve involving loss of retinal ganglion cells in a characteristic pattern of optic neuropathy. ^[16]
• High myopia usually describes myopia of −6. 00 or more. ^[5] People with high myopia are more likely to have retinal detachments^[17] and primary open angle glaucoma. Retinal detachment is a disorder of the Eye in which the Retina peels away from its underlying layer of support tissue Glaucoma is a group of diseases of the Optic nerve involving loss of retinal ganglion cells in a characteristic pattern of optic neuropathy. ^[18] They are also more likely to experience floaters, shadow-like shapes which appear singly or in clusters in the field of vision. Floaters are deposits of various size shape consistency Refractive The term visual field is sometimes used as a Synonym to Field of view, though they do not designate the same thing Roughly 30% of myopes have high myopia. ^[10]

Age of onset

Myopia is sometimes classified by the age of onset:^[2]

• Congenital myopia, also known as infantile myopia, is present at birth and persists through infancy. ^[8]
• Youth onset myopia occurs prior to age 20. ^[8]

• School myopia appears during childhood, particularly the school-age years. ^[19] This form of myopia is attributed to the use of the eyes for close work during the school years. ^[5]

• Adult onset myopia

• Early adult onset myopia occurs between ages 20 and 40. ^[8]
• Late adult onset myopia occurs after age 40. ^[8]

Epidemiology

The global prevalence of refractive errors has been estimated from 800 million to 2. 3 billion. ^[20] The incidence of myopia within sampled population often varies with age, country, sex, race, ethnicity, occupation, environment, and other factors. An organism's sex is defined by the gametes it produces males produce male gametes (spermatozoa or Sperm) while females produce female gametes (ova or Egg cells; individual The term race or racial group usually refers to the concept of categorizing Humans into Populations or groups on the basis of various sets ^[10][21] Variability in testing and data collection methods makes comparisons of prevalence and progression difficult. ^[22]

In some areas, such as Japan, Singapore and Taiwan, up to 44% of the adult population is myopic. For a topic outline on this subject see List of basic Japan topics. Singapore Taiwan ( Taiwanese: Tâi-oân/Tāi-oân (historically 大灣/台員/大員/台圓/大圓/台窩灣 is an Island in East Asia.

A recent study involving first-year undergraduate students in the United Kingdom found that 50% of British whites and 53. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located 4% of British Asians were myopic. ^[23]

In Australia, the overall prevalence of myopia (worse than −0. For a topic outline on this subject see List of basic Australia topics. 50 diopters) has been estimated to be 77%. ^[24] In one recent study, less than 1 in 10 (8. 4%) Australian children between the ages of 4 and 12 were found to have myopia greater than −0. 50 diopters. ^[25] A recent review found that 16. 4% of Australians aged 40 or over have at least −1. 00 diopters of myopia and 2. 5% have at least −5. 00 diopters. ^[26]

In Brazil, a 2005 study estimated that 6. |utc_offset = -2 to -4 |time_zone_DST = BRST |utc_offset_DST = -2 to -5 |cctld 4% of Brazilians between the ages of 12 and 59 had −1. 00 diopter or myopia or more, compared with 2. 7% of the indigenous people in northwestern Brazil. ^[27] Another found nearly 1 in 8 (13. 3%) of the students in one city were myopic. ^[28]

In Greece, the prevalence of myopia among 15 to 18 year old students was found to be 36. Greece (Ελλάδα transliterated: Elláda, historically, Ellás,) officially the Hellenic Republic (Ελληνική Δημοκρατία 8%. ^[29]

In India, the prevalence of myopia in the general population has been reported to be only 6. India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country 9%. ^[30][29]

A recent review found that 26. 6% of Western Europeans aged 40 or over have at least −1. 00 diopters of myopia and 4. 6% have at least −5. 00 diopters. ^[31]

In the United States, the prevalence of myopia has been estimated at 20%. The United States of America —commonly referred to as the ^[10] Nearly 1 in 10 (9. 2%) American children between the ages of 5 and 17 have myopia. ^[32] Approximately 25% of Americans between the ages of 12 and 54 have the condition. ^[33] A recent review found that 25. 4% of Americans aged 40 or over have at least −1. 00 diopters of myopia and 4. 5% have at least −5. 00 diopters. ^[34]

A study of Jordanian adults aged 17 to 40 found that over half (53. 7%) were myopic. ^[35]

Ethnicity and race

The prevalence of myopia has been reported as high as 70-90% in some Asian countries. 30-40% in Europe and the United States, and 10-20% in Africa. ^[21]

Myopia is less common in black and African people. The term black people usually refers to a racial group of Humans with dark Skin color, but the term has also been used to categorise a number of diverse ^[10] In Americans between the ages of 12 and 54, myopia has been found to affect blacks less than whites^[33]. Asians had the highest prevalence (78. 5%), followed by Hispanics (13. 2%). Whites had the lowest prevalence of myopia (4. 4%), which was not significantly different from African Americans (6. 6%). For hyperopia, whites had the highest prevalence (19. 3%), followed by Hispanics (12. 7%). Asians had the lowest prevalence of hyperopia (6. 3%) and were not significantly different from African Americans (6. 4%). For astigmatism, Asians and Hispanics had the highest prevalences (33. Astigmatism is an optical defect whereby vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina 6% and 36. 9%, respectively) and did not differ from each other (P = . In statistical Hypothesis testing the p-value is the Probability of obtaining a result at least as extreme as the one that was actually observed given 17). African Americans had the lowest prevalence of astigmatism (20. 0%), followed by whites (26. 4%). ^[36]

Education, intelligence, and IQ

A number of studies have shown that the prevalence of myopia increases with level of education^[33][29] and many studies have shown a relationship between myopia and IQ. An Intelligence Quotient or IQ is a score derived from one of several different Standardized tests attempting to measure Intelligence. However, care must be taken in interpreting these results as correlation does not imply causation. Correlation does not imply causation is a phrase used in the Sciences and Statistics to emphasize that Correlation between two variables does not imply

According to Arthur Jensen, myopes average 7-8 IQ points higher than non-myopes. Arthur Jensen (born August 24 1923) is a Professor Emeritus of Educational psychology at the University of California Berkeley. The relationship also holds within families, and siblings with a higher degree of refraction error average higher IQs than siblings with less refraction error. A refractive error, or refraction error, is an error in the focusing of Light by the Eye and a frequent reason for reduced Visual acuity Jensen believes that this indicates myopia and IQ are pleiotropically related as they are caused or influenced by the same genes. Pleiotropy occurs when a single Gene influences multiple phenotypic traits Consequently a new Mutation in the gene will have an effect on all No specific mechanism that could cause a relationship between myopia and IQ has yet been identified.

Etiology and pathogenesis

Because in the most common, "simple" myopia, the eye length is too long, any etiologic explanation must account for such axial elongation. Etiology (alternatively aetiology, aitiology) is the study of causation. To date, no single theory has been able to satisfactorily explain this elongation. The word theory has many distinct meanings in different fields of Knowledge, depending on their methodologies and the context of discussion.

In the early 1900s, William Bates controversially asserted that myopia, as with all refractive errors, resulted from a particular type of "eyestrain" that was itself a result of "mental strain". William Horatio Bates ( December 23, 1860 - July 10, 1931) was an American Physician who practiced ophthalmology and developed what ^[37] He stated that the shape of the eyeball responded instantaneously to the action of the extraocular muscles upon it^[38] and that myopia was produced due to contraction of the inferior oblique and superior oblique muscles which lengthened the eye. The extraocular muscles are the six Muscles that control the movements of the (human eye. The Obliquus oculi inferior (inferior oblique is a thin narrow muscle placed near the anterior margin of the floor of the orbit. For the abdominal muscle see External oblique muscle The superior oblique muscle, or obliquus oculi superior, is a fusiform Muscle in the ^[39] According to Bates, myopia was associated with a "strain" to see distance objects rather than near work. ^[40] Bates theories were rejected by mainstream ophthalmologists of his time and remain so today. ^[41][42]

In the mid-1900s, mainstream ophthalmologists and optometrists believed myopia to be primarily hereditary; the influence of near work in its development seemed "incidental" and the increased prevalence of the condition with increasing age was viewed as a "statistical curiosity". ^[3][4][43]

Among mainstream researchers and eye care professionals, myopia is now thought to be a combination of genetic and environmental factors. An eye care professional is an individual who provides a service related to the Eyes or vision. ^[8][19]

There are currently two basic mechanisms believed to cause myopia: form deprivation (also known as pattern deprivation^[44]) and optical defocus. In Optics, defocus is the one aberration familiar to nearly everyone who has ever needed eyeglasses or used a camera videocamera microscope telescope or binoculars ^[45] Form deprivation occurs when the image quality on the retina is reduced; optical defocus occurs when light focuses in front of or behind the retina. The vertebrate retina is a light sensitive part inside the inner layer of the Eye. Numerous experiments with animals have shown that myopia can be artificially generated by inducing either of these conditions. In animal models wearing negative spectacle lenses, axial myopia has been shown to occur as the eye elongates to compensate for optical defocus. ^[45] The exact mechanism of this image-controlled elongation of the eye is still unknown. It has been suggested that accommodative lag leads to blur (i. e. optical defocus) which in turn stimulates axial elongation and myopia. ^[46]

Theories

• Combination of genetic and environmental factors — In China, myopia is more common in those with higher education background^[47] and some studies suggest that near work may exacerbate a genetic predisposition to develop myopia. ^[48] Other studies have shown that near work (reading, computer games) may not be associated with myopic progression, however. ^[49] A "genetic susceptibility" to environmental factors has been postulated as one explanation for the varying degrees of myopia among individuals or populations,^[50] but there exists some difference of opinion as to whether it exists. ^[19][51] High heritability simply means that most of the variation in a particular population at a particular time is due to genetic differences. If the environment changes — as, for example, it has by the introduction of televisions and computers — the incidence of myopia can change as a result, even though heritability remains high. From a slightly different point of view it could be concluded that — determined by heritage — some people are at a higher risk to develop myopia when exposed to modern environmental conditions with a lot of extensive near work like reading. In other words, it is often not the myopia itself which is inherited, but the reaction to specific environmental conditions — and this reaction can be the onset and the progression of myopia.

• Genetic factors — The wide variability of the prevalence of myopia in different ethnic groups has been reported as additional evidence supporting the role of genetics in the development of myopia. ^[52] Measures of the heritability of myopia have yielded figures as high as 89%, and recent research has identified genes that may be responsible: defective versions of the PAX6 gene seem to be associated with myopia in twin studies [1]. In Genetics, Heritability is the proportion of phenotypic variation in a population that is attributable to genetic variation among individuals History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Paired box gene 6 (aniridia keratitis, also known as PAX6, is a Gene in humans and other animals Twin studies are one of a family of designs in Behavior genetics which aid the study of individual differences by highlighting the role of environmental and genetic Under this theory, the eye is slightly elongated front to back as a result of faults during development, causing images to be focused in front of the retina rather than directly on it. In Geometrical optics, a focus, also called an image point, is the point where Light rays originating from a point on the object converge. The vertebrate retina is a light sensitive part inside the inner layer of the Eye. It is usually discovered during the pre-teen years between eight and twelve years of age. It most often worsens gradually as the eye grows during adolescence and then levels off as a person reaches adulthood. Genetic factors can work in various biochemical ways to cause myopia, a weak or degraded connective tissue is a very essential one. Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, Muscle, and Nervous tissue) Genetic factors include an inherited, increased susceptibility for environmental influences like excessive near work, and the fact that some people do not develop myopia in spite of very adverse conditions is a clear indication that heredity is involved somehow in any case.

• Environmental factors — It has been suggested that a genetic susceptibility to myopia does not exist. ^[19] A high heritability of myopia (as for any other condition) does not mean that environmental factors and lifestyle have no effect on the development of the condition. Some recommend a variety of eye exercises to strengthen the ciliary muscle. The Bates method for "better eyesight" was developed by eye-care physician William Horatio Bates, M The Ciliary Muscle is a muscle in the eye that controls the eye's accommodation for viewing objects at varying distances Other theories suggest that the eyes become strained by the constant extra work involved in "nearwork" and get stuck in the near position, and eye exercises can help loosen the muscles up thereby freeing it for far vision. These primarily mechanical models appear to be in contrast to research results, which show that the myopic elongation of the eye can be caused by the image quality, with biochemical processes as the actuator. Common to both views is, however, that extensive near work and corresponding accommodation can be essential for the onset and the progression of myopia.

One Austrian study confirmed that the axial length of the eye does mildly increase while reading, but attributed this elongation due to contraction of the ciliary muscle during accommodation (the process by which the eye increases optical power to maintain a clear image focus), not "squeezing" of the extraocular muscles. Accommodation is the process by which the:eye increases Optical power to maintain a clear image ( focus) on an object as it draws near the eye ^[53]

Near work and nightlight exposure in childhood have been hypothesized as environmental risk factors for myopia. ^[54] Although one initial study indicated a strong association between myopia and nightlight exposure,^[55] recent research has found none. ^{[54][56][57][58]}

• Near work. Near work has been implicated as a contributing factor to myopia in some studies, but refuted in others. ^[59] One recent study suggested that students exposed to extensive "near work" may be at a higher risk of developing myopia, whereas extended breaks from near work during summer or winter vacations may retard myopic progression [2]. Near work in certain cultures (e. g. Vanuatu) does not result in greater myopia[3][4][5][6]. Vanuatu, officially the Republic of Vanuatu ( French: République de Vanuatu, Bislama: Ripablik blong Vanuatu) is an Island It has been hypothesized that this outcome may be a results of genetics or environmental factors such as diet or over-illumination, changes in which seem to occur in Asian, Vanuatu and Inuit cultures acclamating to intensive early studies[7]. Over-illumination is the presence of lighting intensity ( Illuminance) beyond that required for a specified activity
• Diet and nutrition - One 2002 article suggested that myopia may be caused by over-consumption of bread in childhood, or in general by diets too rich in carbohydrates, which can lead to chronic hyperinsulinemia. Carbohydrates (from ' Hydrates of Carbon ' or saccharides ( Greek σάκχαρον meaning " Sugar " are the most Hyperinsulinemia, present in people with Diabetes mellitus type 2 or Insulin resistance where excess levels of circulating Insulin are in the blood Various other components of the diet, however, were made responsible for contributing to myopia as well, as summarized in a documentation.
• Stress has been postulated as a factor in the development of myopia. ^[60]

Relevant research

• A Turkish study found that accommodative convergence, rather than accommodation, may be a factor in the onset and progression of myopia in adults. Accommodative convergence is that portion of the range of inward rotation of both Eyes (i ^[61]
• A recent Polish study revealed that "with-the-rule astigmatism" may lead to the creation of myopia. ^[62]

Presbyopia and the 'payoff' for the nearsighted

Many people with myopia are able to read comfortably without eyeglasses even in advanced age. Myopes considering refractive surgery are advised that this may be a disadvantage after the age of 40 when the eyes become presbyopic and lose their ability to accommodate or change focus. Refractive eye surgery is any Eye surgery used to improve the refractive state of the Eye and decrease or eliminate dependency on Glasses or Contact Presbyopia (Greek word "presbys" (πρέσβυς meaning "old person" describes the condition where the Eye exhibits a progressively diminished ability Accommodation is the process by which the:eye increases Optical power to maintain a clear image ( focus) on an object as it draws near the eye

Diagnosis

A diagnosis of myopia is typically confirmed during an eye examination by an ophthalmologist or an optometrist. An eye examination is a battery of tests performed by an Optometrist or Ophthalmologist assessing vision and ability to focus on and discern Ophthalmology is the branch of Medicine which deals with the diseases and surgery of the visual pathways including the Eye, Brain Optometry is a health care profession concerned with Eyes and related structures as well as vision, Visual systems and vision information Frequently an autorefractor or retinoscope is used to give an initial objective assessment of the refractive status of each eye, then a phoropter is used to subjectively refine the patient's eyeglass prescription. An autorefractor or automated refractor is a computer-controlled machine used during an Eye examination to provide an objective measurement of a person's refractive Retinoscopy is a technique to obtain an objective measurement of the refractive condition of a patient's Eyes. A phoropter (or phoroptor) is an instrument commonly used by Optometrists and Ophthalmologists during an Eye examination to measure an individual's An eyeglass prescription is a written order by an Optometrist or Ophthalmologist to an Optician for Eyeglasses.

Treatment, management, and prevention

Eyeglasses, contact lenses, and refractive surgery are the primary options to treat the visual symptoms of those with myopia. Glasses, also called eyeglasses or spectacles, are frames bearing lenses worn in front of the Eyes normally for vision correction, A contact lens (also known simply as a contact) is a corrective, cosmetic, or therapeutic lens usually placed on the Cornea Refractive eye surgery is any Eye surgery used to improve the refractive state of the Eye and decrease or eliminate dependency on Glasses or Contact Orthokeratology is the practice of using special rigid contact lenses to flatten the cornea to reduce myopia. Orthokeratology ( Ortho-K, also known as "dream lens" and "dream vision" is the use of rigid gas-permeable Contact lenses normally worn only at

Eye-exercises and biofeedback

Practitioners and advocates of alternative therapies often recommend eye exercises and relaxation techniques such as the Bates method. The term alternative medicine, as used in the modern western world encompasses any healing practice "that does not fall within the realm of conventional Medicine. The Bates method for "better eyesight" was developed by eye-care physician William Horatio Bates, M However, the efficacy of these practices is disputed by scientists and eye care practitioners. ^[41] A 2005 review of scientific papers on the subject concluded that there was "no clear scientific evidence" that eye exercises were effective in treating myopia. ^[42]

In the eighties and nineties, there was a flurry of interest in biofeedback as a possible treatment for myopia. Biofeedback is a form of Alternative medicine that involves measuring a subject's quantifiable bodily functions such as Blood pressure, Heart rate, A 1997 review of this biofeedback research concluded that "controlled studies to validate such methods . . . have been rare and contradictory. "^[63] It was found in one study that myopes could improve their visual acuity with biofeedback training, but that this improvement was "instrument-specific" and did not generalise to other measures or situations. ^[64] In another study an "improvement" in visual acuity was found but the authors concluded that this could be a result of subjects learning the task. ^[65] Finally, in an evaluation of a training system designed to improve acuity, "no significant difference was found between the control and experimental subjects". ^[66]

Prevention

There is no universally accepted method of preventing myopia. ^[8] Some clinicians and researchers recommend plus power (convex) lenses in the form of single vision reading lenses or bifocals. Bifocals are Eyeglasses whose Corrective lenses each contain regions with two distinct Optical powers Bifocals are most commonly prescribed to people with ^[8][67] A recent Malaysian study reported in New Scientist^[68] suggested that undercorrection of myopia caused more rapid progression of myopia,^[69] However, the reliability of this data has been called into question. New Scientist is a weekly International science magazine and website covering recent developments in science and technology for a general English -speaking ^[70] Many myopia treatment studies suffer from any of a number of design drawbacks: small numbers, lack of adequate control group, failure to mask examiners from knowledge of treatments used, etc. The sample size of a Statistical sample is the number of observations that constitute it Scientific controls allow Experiments to study one Variable at a time and are a vital part of the Scientific method. The blind method is a part of the Scientific method, used to prevent research outcomes from being influenced by either the Placebo effect or the Observer

Pirenzepine eyedrops had a limited effect on retarding myopic progression in a recent, placebo-control, double-blinded prospective controlled study. Pirenzepine (marketed by Boehringer Ingelheim under the trade-name Gastrozepin) is used in the treatment of Peptic ulcers, as it reduces Gastric acid secretion A longitudinal study is a Correlational research study that involves repeated observations of the same items over long periods of time - often many decades ^[71]

Myopia control

Various methods have been employed in an attempt to decrease the progression of myopia. ^[45] Altering the use of eyeglasses between full-time, part-time, and not at all does not appear to alter myopia progression. ^[72][73] Bifocal and progressive lenses have not shown significant differences in altering the progression of myopia. Progressive lenses, also called progressive addition lenses (PAL, progressive power lenses, graduated lenses, no-line Bifocals ^[45]

Myopia as metaphor

The terms myopia and myopic (or the common terms short sightedness or short sighted) have also been used metaphorically to refer to cognitive thinking and decision making that is narrow sighted or lacking in concern for wider interests or longer-term consequences. Metaphor (from the Greek: μεταφορά - metaphora, meaning "transfer" is language that directly compares seemingly unrelated subjects

See also

• Astigmatism (eye)
• Hyperopia (longsightedness)
• Optician
• Relaxed selection

References

External links

• pupilEyes - Learn how Myopia happens
• Myopia Manual — an impartial documentation of all the reasons, therapies and recommendations — summary of scientific publications, status February 2008
• VisionSimulations.com |What the world looks like to people with various diseases and conditions of the eye
• The Wildsoet Lab - Myopia research at the University of California, Berkeley
• Scottish Sensory Centre - Medical Info on Myopia

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