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84-444: SNEC manages more than 380,000 patient visits and over 41,000 surgeries annually. Its services include Corneal & External Eye Disease, Cataract & Comprehensive Ophthalmology, Glaucoma , Neuro-Ophthalmology , Ocular Inflammation & Immunology, Oculoplastic , Paediatric Ophthalmology & Adult Strabismus , Refractive Surgery , and Medical & Surgical Retina. SNEC undertakes 100% video recording of major surgeries and

168-404: A desperate and cheap substitute for regular ethanol alcoholic beverages . It is important that people be examined by someone specializing in low vision care prior to other rehabilitation training to rule out potential medical or surgical correction for the problem and to establish a careful baseline refraction and prescription of both normal and low vision glasses and optical aids. Only a doctor

252-505: A reduction of vision . Nuclear cataracts typically cause greater impairment of distance vision than of near vision. Those with posterior subcapsular cataracts usually complain of glare as their major symptom. The severity of cataract formation, assuming no other eye disease is present, is judged primarily by a visual acuity test. Other symptoms include frequent changes of glasses and colored halos due to hydration of lens. Congenital cataracts can result in amblyopia if not treated in

336-400: A vitrectomy —without ever having had cataract surgery—will experience progression of nuclear sclerosis after the operation. This may be because the native vitreous humor is different from the solutions used to replace the vitreous (vitreous substitutes), such as BSS Plus . This may also be because the native vitreous humour contains ascorbic acid which helps neutralize oxidative damage to

420-429: A 1.5-fold risk of reporting perceived discrimination and of these individuals, there was a 2-fold risk of loneliness and 4-fold risk of reporting a lower quality of life.  Among adults with visual impairment, the prevalence of moderate loneliness is 28.7% (18.2% in general population) and prevalence of severe loneliness is 19.7% (2.7% in general population).  The risk of depression and anxiety are also increased in

504-434: A State plan approved under title X or XVI as in effect for October 1972 and received aid under such plan (on the basis of blindness) for December 1973, so long as he is continuously blind as so defined. Vision impairment for a few seconds, or minutes, may occur due to any of a variety of causes, some serious and requiring medical attention. Visual impairments may take many forms and be of varying degrees. Visual acuity alone

588-592: A building extension of SGD $ 50 million, establishing an eight-story building consisting of two floors of outpatient clinics , 5 operating rooms, and two floors of SERI's research clinics and laboratories. In 2012, SNEC started a partnership with Duke-NUS that led to the creation of an ophthalmology and visual sciences academic programme. In August 2019, the SNEC Myopia Centre was launched. This facility allows specialised management of myopia prevention, management and education. Cataract A cataract

672-437: A condition in which a person's circadian rhythm , normally slightly longer than 24 hours, is not entrained (synchronized) to the light–dark cycle. The most common causes of visual impairment globally in 2010 were: The most common causes of blindness worldwide in 2010 were: About 90% of people who are visually impaired live in the developing world . Age-related macular degeneration, glaucoma, and diabetic retinopathy are

756-418: A correcting lens. An eye which is accompanied by a limitation in the fields of vision such that the widest diameter of the visual field subtends an angle no greater than 20 degrees shall be considered for purposes of the first sentence of this subsection as having a central visual acuity of 20/200 or less. An individual shall also be considered to be blind for purposes of this title if he is blind as defined under

840-680: A different classification and includes lamellar, polar, and sutural cataracts. Cataracts can be classified by using the lens opacities classification system LOCS III. In this system, cataracts are classified based on type as nuclear, cortical, or posterior. The cataracts are further classified based on severity on a scale from 1 to 5. The LOCS III system is highly reproducible. Risk factors such as UVB exposure and smoking can be addressed. Although no means of preventing cataracts has been scientifically proven, wearing sunglasses that block ultraviolet light may slow their development. While adequate intake of vitamins A , C , and E may protect against

924-522: A full audit of outcomes, as well as the pursuit of high-impact translational research. On 3 March 1989, SNEC was incorporated, and commenced operations in October 1990 with Professor Arthur Lim appointed as its founding medical director. Lim was considered the ‘father of ophthalmology’ in Southeast Asia. SNEC was officially opened in 1991 by then Health Minister, Yeo Cheow Tong . In 1999, SNEC underwent

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1008-710: A heterogonous mechanism associated with structural change and chronic inflammation. In addition, often pediatric glaucoma differs greatly in cause and management from the glaucoma developed by adults. Currently, the best sign of pediatric glaucoma is an IOP of 21 mm Hg or greater present within a child. One of the most common causes of pediatric glaucoma is cataract removal surgery, which leads to an incidence rate of about 12.2% among infants and 58.7% among 10-year-olds. Childhood blindness can be caused by conditions related to pregnancy, such as congenital rubella syndrome and retinopathy of prematurity . Leprosy and onchocerciasis each blind approximately 1 million individuals in

1092-405: A low vision specialist (optometrist or ophthalmologist) is to maximize the functional level of a patient's vision by optical or non-optical means. Primarily, this is by use of magnification in the form of telescopic systems for distance vision and optical or electronic magnification for near tasks. People with significantly reduced acuity may benefit from training conducted by individuals trained in

1176-460: A needle-shaped instrument, Galen attempted to remove the cataract-affected lens of the eye. Muslim ophthalmologist Ammar Al-Mawsili , in his The Book of Choice in Ophthalmology , written circa 1000 CE, wrote of his invention of a syringe and the technique of cataract extraction while experimenting with it on a patient. In 1468 Abiathar Crescas , a Jewish physician and astrologer of

1260-420: A person can do any work for which eyesight is essential, not just one particular job (such as their job before becoming blind). In practice, the definition depends on individuals' visual acuity and the extent to which their field of vision is restricted. The Department of Health identifies three groups of people who may be classified as severely visually impaired. The Department of Health also state that

1344-458: A person is more likely to be classified as severely visually impaired if their eyesight has failed recently or if they are an older individual, both groups being perceived as less able to adapt to their vision loss. In the United States, any person with vision that cannot be corrected to better than 20/200 in the better eye, or who has 20 degrees ( diameter ) or less of visual field remaining,

1428-441: A quarter mile (400 m) and walking up stairs, as compared to those with normal vision. Older adults with vision loss are at an increased risk of memory loss, cognitive impairment, and cognitive decline. Studies demonstrate an association between older adults with visual impairment and a poor mental health; discrimination was identified as one of the causes of this association.  Older adults with visual impairment have

1512-460: A result, corneal scarring from all causes is now the fourth greatest cause of global blindness. Eye injuries , most often occurring in people under 30, are the leading cause of monocular blindness (vision loss in one eye) throughout the United States . Injuries and cataracts affect the eye itself, while abnormalities such as optic nerve hypoplasia affect the nerve bundle that sends signals from

1596-485: A therapeutic purpose. HBOT can have several side effects, including the long-term development of cataracts. This is rare and generally associated with multiple HBOT exposures over a long period. As it does not usually become symptomatic during HBOT, it may often go unrecognised and is probably under-reported. Evidence is emerging that lifetime dosage of oxygen may be a precipitating factor in the development of age-related cataracts. Nuclear cataracts have been hypothesized to be

1680-444: A timely manner. Age is the most common cause of cataracts. Lens proteins denature and degrade over time, and this process is accelerated by diseases such as diabetes mellitus and hypertension . Environmental factors, including toxins, radiation, and ultraviolet light have cumulative effects which are worsened by the loss of protective and restorative mechanisms due to alterations in gene expression and chemical processes within

1764-445: A trend to overuse cataract surgery has been noted, which may lead to disappointing results. Phacoemulsification is the most widely used cataract surgery in the developed world. This procedure uses ultrasonic energy to emulsify the cataract lens. Phacoemulsification typically comprises six steps: A Cochrane review found little to no difference in visual acuity as a function of the size of incisions made for phacoemulsification in

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1848-995: Is a cloudy area in the lens of the eye that leads to a decrease in vision of the eye. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colours, blurry or double vision , halos around light, trouble with bright lights, and difficulty seeing at night . This may result in trouble driving, reading, or recognizing faces. Poor vision caused by cataracts may also result in an increased risk of falling and depression . Cataracts cause 51% of all cases of blindness and 33% of visual impairment worldwide. Cataracts are most commonly due to aging but may also occur due to trauma or radiation exposure, be present from birth , or occur following eye surgery for other problems. Risk factors include diabetes , longstanding use of corticosteroid medication, smoking tobacco , prolonged exposure to sunlight , and alcohol . The underlying mechanism involves accumulation of clumps of protein or yellow-brown pigment in

1932-407: Is a condition in which months or years after successful cataract surgery, vision deteriorates or problems with glare and light scattering recur, usually due to thickening of the back or posterior capsule surrounding the implanted lens, so-called 'posterior lens capsule opacification'. Growth of natural lens cells remaining after the natural lens was removed may be the cause, and the younger the patient,

2016-583: Is a useful predictor of overall well-being, and routine physical activity reduces the risk of developing chronic diseases and disability. Older adults with visual impairment (including glaucoma, age-related macular degeneration, and diabetic retinopathy) have decreased physical activity as measured with self-reports and accelerometers. The US National Health and Nutrition Examination Survey (NHANES) showed that people with corrected visual acuity of less than 20/40 spent significantly less time in moderate to vigorous physical activity. Age-related macular degeneration

2100-591: Is advised to move cautiously and avoid straining or heavy lifting for about a month. The eye is usually patched on the day of surgery and use of an eye shield at night is often suggested for several days after surgery. In all types of surgery, the cataractous lens is removed and replaced with an artificial lens, known as an intraocular lens , which stays in the eye permanently. Intraocular lenses are usually monofocal, correcting for either distance or near vision. Multifocal lenses may be implanted to improve near and distance vision simultaneously, but these lenses may increase

2184-430: Is also associated with a 50% decrease in physical activity–however physical activity is protective against age-related macular degeneration progression. In terms of mobility, those with visual impairment have a slower gait speed than those without visual impairment; however, the rate of decline remains proportional with increasing age in both groups. Additionally, the visually impaired also have greater difficulty walking

2268-662: Is an autosomal recessive disorder associated with cuneiform cataracts and nuclear sclerosis. Basal-cell nevus and pemphigus have similar associations. Cigarette smoking has been shown to increase the risk of age-related cataract and nuclear cataract. Evidence is conflicting over the effect of alcohol. Some surveys have shown a link, but others that followed people over longer terms have not. Low vitamin C intake and serum levels have been associated with greater cataract rates. However, use of supplements of vitamin C has not demonstrated benefit. Some medications, such as systemic, topical, or inhaled corticosteroids , may increase

2352-521: Is an eye disease often characterized by increased pressure within the eye or intraocular pressure (IOP). Glaucoma causes visual field loss as well as severs the optic nerve. Early diagnosis and treatment of glaucoma in patients is imperative because glaucoma is triggered by non-specific levels of IOP. Also, another challenge in accurately diagnosing glaucoma is that the disease has four causes: 1) inflammatory ocular hypertension syndrome (IOHS); 2) severe uveitic angle closure; 3) corticosteroid-induced; and 4)

2436-412: Is characterized by decreased peripheral vision and trouble seeing at night. Advances in mapping of the human genome have identified other genetic causes of low vision or blindness. One such example is Bardet–Biedl syndrome . Rarely, blindness is caused by the intake of certain chemicals. A well-known example is methanol , which is only mildly toxic and minimally intoxicating, and breaks down into

2520-483: Is considered legally blind or eligible for disability classification and possible inclusion in certain government sponsored programs. The terms partially sighted , low vision , legally blind and totally blind are used by schools, colleges, and other educational institutions to describe students with visual impairments. They are defined as follows: In 1934, the American Medical Association adopted

2604-663: Is not always a good predictor of an individual's function. Someone with relatively good acuity (e.g., 20/40) can have difficulty with daily functioning, while someone with worse acuity (e.g., 20/200) may function reasonably well if they have low visual demands. Best-corrected visual acuity differs from presenting visual acuity; a person with a "normal" best corrected acuity can have "poor" presenting acuity (e.g. individual who has uncorrected refractive error). Thus, measuring an individual's general functioning depends on one's situational and contextual factors, as well as access to treatment. The American Medical Association has estimated that

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2688-684: Is of uncertain benefit. Diagnosis is by an eye exam . The World Health Organization (WHO) estimates that 80% of visual impairment is either preventable or curable with treatment. This includes cataracts, the infections river blindness and trachoma , glaucoma, diabetic retinopathy, uncorrected refractive errors, and some cases of childhood blindness. Many people with significant visual impairment benefit from vision rehabilitation , changes in their environment, and assistive devices. As of 2015 , there were 940 million people with some degree of vision loss. 246 million had low vision and 39 million were blind. The majority of people with poor vision are in

2772-429: Is problematic. Manual small incision cataract surgery (MSICS) has evolved from ECCE. In MSICS, the lens is removed through a self-sealing scleral tunnel wound in the sclera which, ideally, is watertight and does not require suturing. Although "small", the incision is still markedly larger than the portal in phacoemulsification. This surgery is increasingly popular in the developing world where access to phacoemulsification

2856-414: Is still limited. Intracapsular cataract extraction (ICCE) is rarely performed. The lens and surrounding capsule are removed in one piece through a large incision while pressure is applied to the vitreous membrane . The surgery has a high rate of complications. The postoperative recovery period (after removing the cataract) is usually short. The patient is usually ambulatory on the day of surgery, but

2940-495: Is the only effective treatment. Cataract surgery is not readily available in many countries, and surgery is needed only if the cataracts are causing problems and generally results in an improved quality of life . About 20 million people worldwide are blind due to cataracts. It is the cause of approximately 5% of blindness in the United States and nearly 60% of blindness in parts of Africa and South America. Blindness from cataracts occurs in about 10 to 40 per 100,000 children in

3024-464: Is unfavorable. Therefore, early intervention is imperative for enabling successful psychological adjustment. Blindness can occur in combination with such conditions as intellectual disability , autism spectrum disorders , cerebral palsy , hearing impairments , and epilepsy . Blindness in combination with hearing loss is known as deafblindness . It has been estimated that over half of completely blind people have non-24-hour sleep–wake disorder ,

3108-570: The Crown of Aragon , famously removed the cataracts of King John II of Aragon , restoring his eyesight. "Cataract" is derived from the Latin cataracta , meaning "waterfall", and from the Ancient Greek καταρράκτης ( katarrhaktēs ), "down-rushing", from καταράσσω ( katarassō ) meaning "to dash down" (from kata -, "down"; arassein , "to strike, dash"). As rapidly running water turns white, so

3192-516: The developing world and are over the age of 50 years. Rates of visual impairment have decreased since the 1990s. Visual impairments have considerable economic costs both directly due to the cost of treatment and indirectly due to decreased ability to work. In 2010, the WHO definition for visual impairment was changed and now follows the ICD-11 . The previous definition which used "best corrected visual acuity"

3276-515: The developing world , and 1 to 4 per 100,000 children in the developed world . Cataracts become more common with age . In the United States, cataracts occur in 68% of those over the age of 80 years. Additionally they are more common in women, and less common in Hispanic and Black people. Signs and symptoms vary depending on the type of cataract, though considerable overlap occurs. People with nuclear sclerotic or brunescent cataracts often notice

3360-692: The Aid to the Blind program in the Social Security Act passed in 1935. In 1972, the Aid to the Blind program and two others combined under Title XVI of the Social Security Act to form the Supplemental Security Income program which states: An individual shall be considered to be blind for purposes of this title if he has central visual acuity of 20/200 or less in the better eye with the use of

3444-619: The Bulgarians, the Byzantine Emperor Basil II blinded as many as 15,000 prisoners taken in the battle, before releasing them. Contemporary examples include the addition of methods such as acid throwing as a form of disfigurement . People with albinism often have vision loss to the extent that many are legally blind, though few of them actually cannot see. Leber congenital amaurosis can cause total blindness or severe sight loss from birth or early childhood. Retinitis pigmentosa

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3528-574: The DNA of lens cells. Ultraviolet light, specifically UVB , has also been shown to cause cataracts, and some evidence indicates sunglasses worn at an early age can slow its development in later life. Microwaves , a type of nonionizing radiation , may cause harm by denaturing protective enzymes (e.g., glutathione peroxidase ), by oxidizing protein thiol groups (causing protein aggregation ), or by damaging lens cells via thermoelastic expansion. The protein coagulation caused by electric and heat injuries whitens

3612-508: The UK, the Certificate of Vision Impairment (CVI) is used to certify people as being severely sight impaired or sight impaired. The accompanying guidance for clinical staff states: "The National Assistance Act 1948 states that a person can be certified as severely sight impaired if they are 'so blind as to be unable to perform any work for which eye sight is essential'". Certification is based on whether

3696-554: The age of 40. Consequently, today cataracts are more common among adults than in children. That is, people face higher chances of developing cataracts as they age. Nonetheless, cataracts tend to have a greater financial and emotional toll upon children as they must undergo expensive diagnosis, long term rehabilitation, and visual assistance. Also, according to the Saudi Journal for Health Sciences, sometimes people experience irreversible amblyopia after pediatric cataract surgery because

3780-513: The ages of 75 and 85. Cataracts affect nearly 22 million Americans age 40 and older. By age 80, more than half of all Americans have cataracts. Direct medical costs for cataract treatment are estimated at $ 6.8 billion annually. In the eastern Mediterranean region, cataracts are responsible for over 51% of blindness. Access to eye care in many countries in this region is limited. Childhood-related cataracts are responsible for 5–20% of world childhood blindness. Vision loss due to cataracts increases

3864-452: The back of the lens adjacent to the capsule (or bag) in which the lens sits. Because light becomes more focused toward the back of the lens, they can cause disproportionate symptoms for their size. An immature cataract has some transparent protein, but with a mature cataract, all the lens protein is opaque. In a hypermature or Morgagnian cataract, the lens proteins have become liquid. Congenital cataract, which may be detected in adulthood, has

3948-497: The case of neurofibromatosis type 2 , juvenile cataract on one or both sides may be noted. Examples of single-gene disorder include Alport's syndrome , Conradi's syndrome , cerebrotendineous xanthomatosis , myotonic dystrophy , and oculocerebrorenal syndrome or Lowe syndrome . The skin and the lens have the same embryological origin and so can be affected by similar diseases. Those with atopic dermatitis and eczema occasionally develop shield ulcer cataracts. Ichthyosis

4032-441: The cataracts prevented the normal maturation of vision prior to operation. Despite the great progress in treatment, cataracts remain a global problem in both economically developed and developing countries. At present, with the variant outcomes as well as the unequal access to cataract surgery, the best way to reduce the risk of developing cataracts is to avoid smoking and extensive exposure to sun light (i.e. UV-B rays). Glaucoma

4116-414: The chance of unsatisfactory vision. Serious complications of cataract surgery include retinal detachment and endophthalmitis . In both cases, patients notice a sudden decrease in vision. In endophthalmitis, patients often describe pain. Retinal detachment frequently presents with unilateral visual field defects, blurring of vision, flashes of light, or floating spots. The risk of retinal detachment

4200-410: The day. Blinding has been used as an act of vengeance and torture in some instances, to deprive a person of a major sense by which they can navigate or interact within the world, act fully independently, and be aware of events surrounding them. An example from the classical realm is Oedipus , who gouges out his own eyes after realizing that he fulfilled the awful prophecy spoken of him. Having crushed

4284-462: The developing world. The number of individuals blind from trachoma has decreased in the past 10 years from 6 million to 1.3 million, putting it in seventh place on the list of causes of blindness worldwide. Central corneal ulceration is also a significant cause of monocular blindness worldwide, accounting for an estimated 850,000 cases of corneal blindness every year in the Indian subcontinent alone. As

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4368-465: The end stage of the far better known phenomenon of hyperbaric myopic shift. Cataracts may be partial or complete, stationary or progressive, hard or soft. Histologically, the main types of age-related cataracts are nuclear sclerosis, cortical, and posterior subcapsular. Nuclear sclerosis is the most common type of cataract, and involves the central or 'nuclear' part of the lens. This eventually becomes hard, or 'sclerotic', due to condensation on

4452-662: The eye and covering the eye with warm butter . References to cataracts and their treatment in Ancient Rome are also found in 29 AD in De Medicinae , the work of the Latin encyclopedist Aulus Cornelius Celsus . Archaeological evidence of eye surgery in the Roman era also exists. Galen of Pergamon (ca. 2nd century CE), a prominent Greek physician , surgeon and philosopher , performed an operation similar to modern cataract surgery. Using

4536-457: The eye to the back of the brain, which can lead to decreased visual acuity. Cortical blindness results from injuries to the occipital lobe of the brain that prevent the brain from correctly receiving or interpreting signals from the optic nerve . Symptoms of cortical blindness vary greatly across individuals and may be more severe in periods of exhaustion or stress. It is common for people with cortical blindness to have poorer vision later in

4620-526: The eye. Vision loss Visual or vision impairment ( VI or VIP ) is the partial or total inability of visual perception . In the absence of treatment such as corrective eyewear, assistive devices, and medical treatment, visual impairment may cause the individual difficulties with normal daily tasks, including reading and walking. The terms low vision and blindness are often used for levels of impairment which are difficult or impossible to correct and significantly impact daily life. In addition to

4704-431: The eye. Oxidative stress associated with lipid peroxidation is an important pathogenic mechanism in cataract formation. Senile cataracts are associated with a decrease in antioxidant capacity in the lens. An increase in oxidative stress in the lens or a decrease in the ability to remove reactive oxygen species can lead to the lens becoming more opaque. Blunt trauma causes swelling, thickening, and whitening of

4788-451: The following definition of blindness: Central visual acuity of 20/200 or less in the better eye with corrective glasses or central visual acuity of more than 20/200 if there is a visual field defect in which the peripheral field is contracted to such an extent that the widest diameter of the visual field subtends an angular distance no greater than 20 degrees in the better eye. The United States Congress included this definition as part of

4872-419: The greater the chance of this occurring. Management involves cutting a small, circular area in the posterior capsule with targeted beams of energy from a laser, called Nd:YAG laser capsulotomy, after the type of laser used. The laser can be aimed very accurately, and the small part of the capsule which is cut falls harmlessly to the bottom of the inside of the eye. This procedure leaves sufficient capsule to hold

4956-413: The highest risk group of patients, the incidence of pseudophakic retinal detachment may be as high as 20%. The risk of endophthalmitis occurring after surgery is less than one in 1000. Corneal edema and cystoid macular edema are less serious but more common, and occur because of persistent swelling at the front of the eye in corneal edema or back of the eye in cystoid macular edema. They are normally

5040-412: The leading cause of blindness. Even where surgical services are available, low vision associated with cataracts may still be prevalent as a result of long waits for, and barriers to, surgery, such as cost, lack of information and transportation problems. In the United States, age-related lens changes have been reported in 42% between the ages of 52 and 64, 60% between the ages 65 and 74, and 91% between

5124-514: The leading causes of blindness in the developed world. Among working-age adults who are newly blind in England and Wales the most common causes in 2010 were: Cataracts are the greying or opacity of the crystalline lens, which can be caused in children by intrauterine infections, metabolic disorders, and genetically transmitted syndromes. Cataracts are the leading cause of child and adult blindness that doubles in prevalence with every ten years after

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5208-445: The lens and because conventional vitreous substitutes do not contain ascorbic acid. Accordingly, for phakic patients requiring a vitrectomy it is becoming increasingly common for ophthalmologists to offer the vitrectomy combined with prophylactic cataract surgery to prevent cataract formation. Hyperbaric oxygen therapy (HBOT) is the administration of 100% oxygen at pressures greater than one-atmosphere absolute pressure (1 ATA) for

5292-407: The lens cortex (outer layer) becoming opaque. They occur when changes in the fluid contained in the periphery of the lens cause fissuring. When these cataracts are viewed through an ophthalmoscope , or other magnification system, the appearance is similar to white spokes of a wheel. Symptoms often include problems with glare and light scatter at night. Posterior subcapsular cataracts are cloudy at

5376-680: The lens fibers. While the swelling normally resolves with time, the white color may remain. In severe blunt trauma, or in injuries that penetrate the eye, the capsule in which the lens sits can be damaged. This damage allows fluid from other parts of the eye to rapidly enter the lens leading to swelling and then whitening, obstructing light from reaching the retina at the back of the eye. Cataracts may develop in 0.7 to 8.0% of cases following electrical injuries . Blunt trauma can also result in star- (stellate) or petal-shaped cataracts. Cataracts can arise as an effect of exposure to various types of radiation. X-rays, one form of ionizing radiation , may damage

5460-774: The lens in place, but removes enough to allow light to pass directly through to the retina. Serious side effects are rare. Posterior capsular opacification is common and occurs following up to one in four operations, but these rates are decreasing following the introduction of modern intraocular lenses together with a better understanding of the causes. Vitreous touch syndrome is a possible complication of intracapsular cataract extraction. Age-related cataracts are responsible for 51% of world blindness, about 20 million people. Globally, cataracts cause moderate to severe disability in 53.8 million (2004), 52.2 million of whom are in low and middle income countries. In many countries, surgical services are inadequate, and cataracts remain

5544-454: The lens nucleus and the deposition of brown pigment within the lens. In its advanced stages, it is called a brunescent cataract. In early stages, an increase in sclerosis may cause an increase in refractive index of the lens. This causes a myopic shift (lenticular shift) that decreases hyperopia and enables presbyopic patients to see at near without reading glasses. This is only temporary and is called second sight. Cortical cataracts are due to

5628-448: The lens that reduces transmission of light to the retina at the back of the eye. Diagnosis is by an eye examination . Wearing sunglasses and a wide brimmed hat, eating leafy vegetables and fruits, and avoiding smoking may reduce the risk of developing cataracts, or slow the process. Early on, the symptoms may be improved with glasses . If this does not help, surgery to remove the cloudy lens and replace it with an artificial lens

5712-496: The lens. Surgery is usually outpatient and usually performed using local anesthesia . About 9 of 10 patients can achieve a corrected vision of 20/40 or better after surgery. Several recent evaluations found that cataract surgery can meet expectations only when significant functional impairment due to cataracts exists before surgery. Visual function estimates such as VF-14 have been found to give more realistic estimates than visual acuity testing alone. In some developed countries,

5796-581: The lens. This same process is what makes the clear albumen of an egg become white and opaque during cooking. The genetic component is strong in the development of cataracts, most commonly through mechanisms that protect and maintain the lens. The presence of cataracts in childhood or early life can occasionally be due to a particular syndrome. Examples of chromosome abnormalities associated with cataracts include 1q21.1 deletion syndrome , cri-du-chat syndrome , Down syndrome , Patau's syndrome , trisomy 18 ( Edward's syndrome ), and Turner's syndrome , and in

5880-419: The loss of one eye equals 25% impairment of the visual system and 24% impairment of the whole person; total loss of vision in both eyes is considered to be 100% visual impairment and 85% impairment of the whole person. Some people who fall into this category can use their considerable residual vision – their remaining sight – to complete daily tasks without relying on alternative methods. The role of

5964-539: The most common cause of blindness. Other disorders that may cause visual problems include age-related macular degeneration , diabetic retinopathy , corneal clouding , childhood blindness , and a number of infections . Visual impairment can also be caused by problems in the brain due to stroke , premature birth , or trauma, among others. These cases are known as cortical visual impairment . Screening for vision problems in children may improve future vision and educational achievement. Screening adults without symptoms

6048-411: The prognosis of eventual blindness are at comparatively high risk of suicide and thus may be in need of supportive services. Many studies have demonstrated how rapid acceptance of the serious visual impairment has led to a better, more productive compliance with rehabilitation programs. Moreover, psychological distress has been reported to be at its highest when sight loss is not complete, but the prognosis

6132-454: The provision of technical aids. Low vision rehabilitation professionals, some of whom are connected to an agency for the blind, can provide advice on lighting and contrast to maximize remaining vision. These professionals also have access to non-visual aids, and can instruct patients in their uses. Older adults with visual impairment are at an increased risk of physical inactivity, slower gait speeds, and fear of falls. Physical activity

6216-440: The range from ≤ 1.5 mm to 3.0 mm. Extracapsular cataract extraction (ECCE) consists of removing the lens manually, but leaving the majority of the capsule intact. The lens is expressed through a 10- to 12-mm incision which is closed with sutures at the end of surgery. ECCE is less frequently performed than phacoemulsification, but can be useful when dealing with very hard cataracts or other situations where emulsification

6300-419: The result of excessive inflammation following surgery, and in both cases, patients may notice blurred, foggy vision. They normally improve with time and with application of anti-inflammatory drops. The risk of either occurring is around one in 100. It is unclear whether NSAIDs or corticosteroids are superior at reducing postoperative inflammation. Posterior capsular opacification, also known as after-cataract,

6384-415: The risk of cataract development. Corticosteroids most commonly cause posterior subcapsular cataracts. People with schizophrenia often have risk factors for lens opacities (such as diabetes, hypertension, and poor nutrition). Second-generation antipsychotic medications are unlikely to contribute to cataract formation. Miotics and triparanol may increase the risk. Nearly every person who undergoes

6468-421: The risk of cataracts, clinical trials have shown no benefit from supplements, although the evidence is mixed, but weakly positive, for a potential protective effect of the carotenoids , lutein and zeaxanthin . The appropriateness of surgery depends on a person's particular functional and visual needs and other risk factors. Cataract removal can be performed at any stage and no longer requires ripening of

6552-526: The risk of dementia in the elderly population, increases the likelihood of falls and road traffic accidents, and by detrimental effects on the quality of life increases mortality. Cataract surgery was first described by the Ayurvedic physician , Suśruta (about 5th century BCE) in Sushruta Samhita in ancient India . Most of the methods mentioned focus on hygiene. Follow-up treatments include bandaging of

6636-457: The substances formaldehyde and formic acid which in turn can cause blindness, an array of other health complications, and death. When competing with ethanol for metabolism, ethanol is metabolized first, and the onset of toxicity is delayed. Methanol is commonly found in methylated spirits , denatured ethyl alcohol , to avoid paying taxes on selling ethanol intended for human consumption. Methylated spirits are sometimes used by alcoholics as

6720-569: The term may have been used metaphorically to describe the similar appearance of mature ocular opacities. In Latin, cataracta had the alternative meaning " portcullis " and the name possibly passed through French to form the English meaning "eye disease" (early 15th century), on the notion of "obstruction". Early Persian physicians called the term nazul-i-ah , or "descent of the water"—vulgarised into waterfall disease or cataract—believing such blindness to be caused by an outpouring of corrupt humour into

6804-399: The various permanent conditions, fleeting temporary vision impairment, amaurosis fugax , may occur, and may indicate serious medical problems. The most common causes of visual impairment globally are uncorrected refractive errors (43%), cataracts (33%), and glaucoma (2%). Refractive errors include near-sightedness , far-sightedness , presbyopia , and astigmatism . Cataracts are

6888-422: The visually impaired; 32.2% report depressive symptoms (12.01% in general population), and 15.61% report anxiety symptoms (10.69% in general population). The subjects making the most use of rehabilitation instruments, who lived alone, and preserved their own mobility and occupation were the least depressed, with the lowest risk of suicide and the highest level of social integration. Those with worsening sight and

6972-400: Was changed to "presenting visual acuity". This change was made as newer studies showed that best-corrected vision overlooks a larger proportion of the population who has visual impairment due to uncorrected refractive errors, and/or lack of access to medical or surgical treatment. Distance vision impairment: Near vision impairment: Severely sight impaired Sight impaired Low vision In

7056-434: Was estimated as about 0.4% within 5.5 years, corresponding to a 2.3-fold risk increase compared to naturally expected incidence, with older studies reporting a substantially higher risk. The incidence is increasing over time in a somewhat linear manner, and the risk increase lasts for at least 20 years after the procedure. Particular risk factors are younger age, male sex, longer axial length, and complications during surgery. In

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