Cataract

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Cataract
Cataract in human eye.png
Magnified view of a cataract seen on examination with a slit lamp
Specialty Ophthalmology
SymptomsFaded colors, blurry vision, halos around light, trouble with bright lights, trouble seeing at night [1]
Complications Falling, depression, blindness [2] [3]
Usual onsetGradual [1]
Causes Aging, trauma, radiation exposure, following eye surgery [1] [4]
Risk factors Diabetes, smoking tobacco, prolonged exposure to sunlight, alcohol [1]
Diagnostic method Eye examination [1]
Prevention Sunglasses, not smoking [1]
Treatment Glasses, cataract surgery [1]
Frequency60 million (2015) [5]

A cataract is a clouding of the lens in the eye which leads to a decrease in vision. [1] Cataracts often develop slowly and can affect one or both eyes. [1] Symptoms may include faded colors, blurry or double vision, halos around light, trouble with bright lights, and trouble seeing at night. [1] This may result in trouble driving, reading, or recognizing faces. [6] Poor vision caused by cataracts may also result in an increased risk of falling and depression. [2] Cataracts cause half of all cases of blindness and 33% of visual impairment worldwide. [3] [7]

Lens (anatomy) transparent structure of eye

The lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina. This adjustment of the lens is known as accommodation. Accommodation is similar to the focusing of a photographic camera via movement of its lenses. The lens is more flat on its anterior side than on its posterior side.

Eye organ that detects light and converts it into electro-chemical impulses in neurons

Eyes are organs of the visual system. They provide animals with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and convert it into electro-chemical impulses in neurons. In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.

Visual impairment, also known as vision impairment or vision loss, is a decreased ability to see to a degree that causes problems not fixable by usual means, such as glasses. Some also include those who have a decreased ability to see because they do not have access to glasses or contact lenses. Visual impairment is often defined as a best corrected visual acuity of worse than either 20/40 or 20/60. The term blindness is used for complete or nearly complete vision loss. Visual impairment may cause people difficulties with normal daily activities such as driving, reading, socializing, and walking.

Contents

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. [1] [4] Risk factors include diabetes, smoking tobacco, prolonged exposure to sunlight, and alcohol. [1] The underlying mechanism involves accumulation of clumps of protein or yellow-brown pigment in the lens that reduces transmission of light to the retina at the back of the eye. [1] Diagnosis is by an eye examination. [1]

Senescence gradual deterioration of function characteristic of most complex lifeforms

Senescence or biologicalaging is the gradual deterioration of functional characteristics. The word senescence can refer either to cellular senescence or to senescence of the whole organism. Organismal senescence involves an increase in death rates and/or a decrease in fecundity with increasing age, at least in the later part of an organism's life cycle.

Congenital cataract disorder of lens

Congenital cataracts refers to a lens opacity present at birth. Congenital cataracts cover a broad spectrum of severity: whereas some lens opacities do not progress and are visually insignificant, others can produce profound visual impairment.

Sunlight portion of the electromagnetic radiation given off by the Sun

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. When the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. When it is blocked by clouds or reflects off other objects, it is experienced as diffused light. The World Meteorological Organization uses the term "sunshine duration" to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter. Other sources indicate an "Average over the entire earth" of "164 Watts per square meter over a 24 hour day".

Prevention includes wearing sunglasses and avoiding smoking. [1] Early on the symptoms may be improved with glasses. [1] If this does not help, surgery to remove the cloudy lens and replace it with an artificial lens is the only effective treatment. [1] Surgery is needed only if the cataracts are causing problems and generally results in an improved quality of life. [1] [8] Cataract surgery is not readily available in many countries, which is especially true for women, those living in rural areas, and those who do not know how to read. [4] [9]

Sunglasses Eyewear for protecting against bright light.

Sunglasses or sun glasses are a form of protective eyewear designed primarily to prevent bright sunlight and high-energy visible light from damaging or discomforting the eyes. They can sometimes also function as a visual aid, as variously termed spectacles or glasses exist, featuring lenses that are colored, polarized or darkened. In the early 20th century, they were also known as sun cheaters.

Glasses accessories that improve vision

Glasses, also known as eyeglasses or spectacles, are devices consisting of glass or hard plastic lenses mounted in a frame that holds them in front of a person's eyes, typically using a bridge over the nose and arms which rest over the ears.

Cataract surgery Eye surgery to remove cataract containing lens and replace it with synthetic lens

Cataract surgery, also called lens replacement surgery, is the removal of the natural lens of the eye that has developed an opacification, which is referred to as a cataract, and its replacement with an intraocular lens. Metabolic changes of the crystalline lens fibers over time lead to the development of the cataract, causing impairment or loss of vision. Some infants are born with congenital cataracts, and certain environmental factors may also lead to cataract formation. Early symptoms may include strong glare from lights and small light sources at night, and reduced acuity at low light levels.

About 20 million people are blind due to cataracts. [4] 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. [9] Blindness from cataracts occurs in about 10 to 40 per 100,000 children in the developing world, and 1 to 4 per 100,000 children in the developed world. [10] Cataracts become more common with age. [1] More than half the people in the United States had cataracts by the age of 80. [1]

Developing country Nation with a low living standard relative to other countries

A developing country is a country with a less developed industrial base and a low Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no clear agreement on which countries fit this category. A nation's GDP per capita compared with other nations can also be a reference point.

Ageing or aging is the process of becoming older. The term refers especially to human beings, many animals, and fungi, whereas for example bacteria, perennial plants and some simple animals are potentially biologically immortal. In the broader sense, ageing can refer to single cells within an organism which have ceased dividing or to the population of a species.

Signs and symptoms

Eye disease simulation, normal vision.jpg
Eye disease simulation, cataract.jpg
An example of normal vision on the left versus vision with cataracts on the right
Bilateral cataracts in an infant due to congenital rubella syndrome Cataracts due to Congenital Rubella Syndrome (CRS) PHIL 4284 lores.jpg
Bilateral cataracts in an infant due to congenital rubella syndrome

Signs and symptoms vary depending on the type of cataract, though considerable overlap occurs. People with nuclear sclerotic or brunescent cataracts often notice 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. [11]

Glare (vision) visual phenomenon

Glare is difficulty of seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night. Because of this, some cars include mirrors with automatic anti-glare functions.

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.

Visual acuity clarity of vision

Visual acuity (VA) commonly refers to the clarity of vision. Visual acuity is dependent on optical and neural factors, i.e., (i) the sharpness of the retinal focus within the eye, (ii) the health and functioning of the retina, and (iii) the sensitivity of the interpretative faculty of the brain.

Causes

Age

Age is the most common cause. [1] [4] 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 the eye. [12]

Trauma

Post traumatic rosette cataract of a 60-year-old male Rosette cataract.jpg
Post traumatic rosette cataract of a 60-year-old male

Blunt trauma causes swelling, thickening, and whitening of 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. [13] Blunt trauma can also result in star- (stellate) or petal-shaped cataracts. [14]

Radiation

Cataracts can arise as an effect of exposure to various types of radiation. X-rays, one form of ionizing radiation, may damage the DNA of lens cells. [15] 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. [16] 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. [15] The protein coagulation caused by electric and heat injuries whitens the lens. [12] This same process is what makes the clear albumen of an egg become white and opaque during cooking.

Genetics

Christmas tree cataract (Diffuse illumination) Chrismas tree cataract.jpg
Christmas tree cataract (Diffuse illumination)

The genetic component is strong in the development of cataracts, [17] 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 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.

Skin diseases

The skin and the lens have the same embryological origin and so can be affected by similar diseases. [18] Those with atopic dermatitis and eczema occasionally develop shield ulcer cataracts. Ichthyosis is an autosomal recessive disorder associated with cuneiform cataracts and nuclear sclerosis. Basal-cell nevus and pemphigus have similar associations.

Smoking and alcohol

Cigarette smoking has been shown to double the rate of nuclear sclerotic cataracts and triple the rate of posterior subcapsular cataracts. [19] Evidence is conflicting over the effect of alcohol. Some surveys have shown a link, but others which followed people over longer terms have not. [20]

Inadequate vitamin C

Low vitamin C intake and serum levels have been associated with greater cataract rates. [21] However, use of supplements of vitamin C has not demonstrated benefit. [22]

Medications

Some medications, such as systemic, topical, or inhaled corticosteroids, may increase the risk of cataract development. [23] [24] Corticosteroids most commonly cause posterior subcapsular cataracts. [24] People with schizophrenia often have risk factors for lens opacities (such as diabetes, hypertension, and poor nutrition) but antipsychotic medications are unlikely to contribute to cataract formation. [25] Miotics [26] and triparanol may increase the risk. [27]

Post-operative

Nearly every person who undergoes a vitrectomy—without ever having had cataract surgery—will experience progression of nuclear sclerosis after the operation. [28] This may be because the native vitreous humor is different to the solutions used to replace the vitreous (vitreous substitutes), such as BSS Plus. [29] This may also be because the native vitreous humour contains ascorbic acid which helps neutralize oxidative damage to the lens and because traditional vitreous substitutes do not contain ascorbic acid. [30] [31] As such, for phakic patients requiring a vitrectomy it is becoming increasingly common for ophthalmologists to offer the vitrectomy with a combined prophylactic cataract surgery procedure to prophylactically prevent cataract formation. [32]

Other diseases

Diagnosis

Classification

Cross-sectional view, showing the position of the human lens Human eye cross-sectional view grayscale.png
Cross-sectional view, showing the position of the human lens
Ultrasound scan of a unilateral cataract seen in a fetus at 20 weeks of pregnancy

Cataracts may be partial or complete, stationary or progressive, or hard or soft. 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 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 cause an increase in refractive index of the lens. [33] This causes a myopic shift (lenticular shift) that decreases hyperopia and enables presbyopic patients to see at near without reading glasses. This is only tempororary and is called second sight.

Cortical cataracts are due to the lens cortex (outer layer) becoming opaque. They occur when changes in the fluid contained in the periphery of the lens causes 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. [33]

Posterior subcapsular cataracts are cloudy at 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 a different classification and includes lamellar, polar, and sutural cataracts. [34] [35]

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. [36]

Prevention

Risk factors such as UVB exposure and smoking can be addressed. Although no means of preventing cataracts has been scientifically proven, wearing sunglasses that counteract ultraviolet light may slow their development. [37] [38] While adequate intake of antioxidants (such as vitamins A, C, and E) has been thought to protect against the risk of cataracts, clinical trials have shown no benefit from supplements; [22] though evidence is mixed, but weakly positive, for a potential protective effect of the nutrients lutein and zeaxanthin. [39] [40] [41] Statin use is somewhat associated with a lower risk of nuclear sclerotic cataracts. [42]

Treatment

Surgical

Cataract surgery, using a temporal-approach phacoemulsification probe (in right hand) and "chopper" (in left hand) being done under operating microscope at a navy medical center Cataract surgery.jpg
Cataract surgery, using a temporal-approach phacoemulsification probe (in right hand) and "chopper" (in left hand) being done under operating microscope at a navy medical center
Slit lamp photo of posterior capsular opacification visible a few months after implantation of intraocular lens in eye, seen on retroillumination Posterior capsular opacification on retroillumination.jpg
Slit lamp photo of posterior capsular opacification visible a few months after implantation of intraocular lens in eye, seen on retroillumination

The appropriateness of surgery depends on a person's particular functional and visual needs and other risk factors. [43] Cataract removal can be performed at any stage and no longer requires ripening of 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. [33]

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. [33] [44] In some developed countries, a trend to overuse cataract surgery has been noted, which may lead to disappointing results. [45]

Phacoemulsification is the most widely used cataract surgery in the developed world. [46] [47] This procedure uses ultrasonic energy to emulsify the cataract lens. Phacoemulsification typically comprises six steps:

Extracapsular cataract extraction (ECCE) consists of removing the lens manually, but leaving the majority of the capsule intact. [48] 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 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 phacoemulsion. This surgery is increasingly popular in the developing world where access to phacoemulsification is still limited.

Intracapsular cataract extraction (ICCE) is rarely performed. [49] 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.

Prognosis

Postoperative care

Slit lamp photo of anterior capsular opacification visible a few months after implantation of intraocular lens in eye, magnified view Anterior capsular opacification.jpg
Slit lamp photo of anterior capsular opacification visible a few months after implantation of intraocular lens in eye, magnified view
A South African woman experiences newfound eyesight after a patch was removed after surgery to remove an eye cataract. Africa Partnerships Vision 2020 2 (10665602364).jpg
A South African woman experiences newfound eyesight after a patch was removed after surgery to remove an eye cataract.

The postoperative recovery period (after removing the cataract) is usually short. The patient is usually ambulatory on the day of surgery, but 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. [43]

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 the chance of unsatisfactory vision. [12]

Complications

Serious complications of cataract surgery include retinal detachment and endophthalmitis. [50] 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 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 the highest risk group of patients, the incidence of pseudophakic retinal detachment may be as high as 20%. [51] [52]

The risk of endophthalmitis occurring after surgery is less than one in 1000. [53]

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. [54] They are normally 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. [55]

Posterior capsular opacification, also known as after-cataract, 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, 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 the lens in place, but removes enough to allow light to pass directly through to the retina. Serious side effects are rare. [56] 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. [57]

Epidemiology

Disability-adjusted life years for cataracts per 100,000 inhabitants in 2004:
no data
<90
90-180
180-270
270-360
360-450
450-540
540-630
630-720
720-810
810-900
900-990
>990 Cataracts world map - DALY - WHO2004.svg
Disability-adjusted life years for cataracts per 100,000 inhabitants in 2004:

Age-related cataracts are responsible for 51% of world blindness, about 20 million people. [59] Globally, cataracts cause moderate to severe disability in 53.8 million (2004), 52.2 million of whom are in low and middle income countries. [60]

In many countries, surgical services are inadequate, and cataracts remain the leading cause of blindness. [59] 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, [61] 60% between the ages 65 and 74, [62] and 91% between the ages of 75 and 85. [61] 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. [63]

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. [64] Childhood-related cataracts are responsible for 5–20% of world childhood blindness. [65]

History

Cataract surgery was first described by the Indian physician, Suśruta (about 5th century BCE) in his manuscript Sushruta Samhita in ancient India. Most of the methods mentioned focus on hygiene. Follow-up treatments include bandaging of the eye and covering the eye with warm butter. [66] 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. [67] Archaeological evidence of eye surgery in the Roman era also exists. [68]

Galen of Pergamon (ca. 2nd century CE), a prominent Greek physician, surgeon and philosopher, performed an operation similar to modern cataract surgery. Using a needle-shaped instrument, Galen attempted to remove the cataract-affected lens of the eye. [69]

Muslim ophthalmologist Ammar Al-Mawsili, in his Choice of Eye Diseases, written circa 1000, wrote of his invention of a syringe and the technique of cataract extraction while experimenting with it on a patient. [70]

Etymology

"Cataract" is derived from the Latin cataracta, meaning "waterfall", and from the Ancient Greek καταρράκτης (katarrhaktēs), "down-rushing", [71] from καταράσσω (katarassō) meaning "to dash down" [72] (from kata-, "down"; arassein, "to strike, dash"). [73] As rapidly running water turns white, so the term may have been used metaphorically to describe the similar appearance of mature ocular opacities. In Latin, cataracta had the alternative meaning "portcullis" [74] and the name possibly passed through French to form the English meaning "eye disease" (early 15th century), on the notion of "obstruction". [75] 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 the eye. [76]

Research

N-Acetylcarnosine drops have been investigated as a medical treatment for cataracts. The drops are believed to work by reducing oxidation and glycation damage in the lens, particularly reducing crystallin crosslinking. [77] [78] Some benefit has been shown in small manufacturer sponsored randomized controlled trials but further independent corroboration is still required. [79]

Femtosecond laser mode-locking, used during cataract surgery, was originally used to cut accurate and predictable flaps in LASIK surgery, and has been introduced to cataract surgery. The incision at the junction of the sclera and cornea and the hole in capsule during capsulorhexis, traditionally made with a handheld blade, needle, and forceps, are dependent on skill and experience of the surgeon. Sophisticated three-dimensional images of the eyes can be used to guide lasers to make these incisions. Nd:YAG laser can also then break up the cataract as in phacoemulsification. [80]

Stem cells have been used in a clinical trial for lens regeneration in twelve children under the age of two with cataracts present at birth. [81] The children were followed for six months, so it is unknown what the long-term results will be, and it is unknown if this procedure would work in adults. [81]

See also

Related Research Articles

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Floater deposits of various size, shape, consistency, refractive index, and motility within the eyes vitreous humour, which is normally transparent

Floaters are deposits of various size, shape, consistency, refractive index, and motility within the eye's vitreous humour, which is normally transparent. At a young age, the vitreous is transparent, but as one ages, imperfections gradually develop. The common type of floater, which is present in most persons' eyes, is due to degenerative changes of the vitreous humour. The perception of floaters is known as myodesopsia, or less commonly as myodaeopsia, myiodeopsia, or myiodesopsia. They are also called Muscae volitantes, or mouches volantes.

Vitrectomy

Vitrectomy is surgery to remove some or all of the vitreous humor from the eye.

LASIK

LASIK or Lasik, commonly referred to as laser eye surgery or laser vision correction, is a type of refractive surgery for the correction of myopia, hyperopia, and astigmatism. The LASIK surgery is performed by an ophthalmologist who uses a laser or microkeratome to reshape the eye's cornea in order to improve visual acuity. For most people, LASIK provides a long-lasting alternative to eyeglasses or contact lenses.

Retinopathy of prematurity (ROP), also called retrolental fibroplasia (RLF) and Terry syndrome, is a disease of the eye affecting prematurely born babies generally having received intensive neonatal care, in which oxygen therapy is used on them due to the premature development of their lungs. It is thought to be caused by disorganized growth of retinal blood vessels which may result in scarring and retinal detachment. ROP can be mild and may resolve spontaneously, but it may lead to blindness in serious cases. As such, all preterm babies are at risk for ROP, and very low birth-weight is an additional risk factor. Both oxygen toxicity and relative hypoxia can contribute to the development of ROP.

Eye surgery medical specialty

Eye surgery, also known as ocular surgery, is surgery performed on the eye or its adnexa, typically by an ophthalmologist. The eye is a very fragile organ, and requires extreme care before, during, and after a surgical procedure to minimise or prevent further damage. An expert eye surgeon is responsible for selecting the appropriate surgical procedure for the patient, and for taking the necessary safety precautions. Mentions of eye surgery can be found in several ancient texts dating back as early as 1800 BC, with cataract treatment starting in the fifth century BC. Today it continues to be a widely practiced type of surgery, having developed various techniques for treating eye problems.

Radial keratotomy

Radial keratotomy (RK) is a refractive surgical procedure to correct myopia (nearsightedness) that was developed in 1974, by Svyatoslav Fyodorov, a Russian ophthalmologist. It has been largely supplanted by newer operations, such as photorefractive keratectomy, LASIK, Epi-LASIK and the phakic intraocular lens.

Refractive surgery medical specialty

Refractive eye surgery is an eye surgery used to improve the refractive state of the eye and decrease or eliminate dependency on glasses or contact lenses. This can include various methods of surgical remodeling of the cornea (keratomileusis), lens implantation or lens replacement. The most common methods today use excimer lasers to reshape the curvature of the cornea. Successful refractive eye surgery can reduce or cure common vision disorders such as myopia, hyperopia and astigmatism, as well as degenerative disorders like keratoconus.

Phacoemulsification

Phacoemulsification is a modern cataract surgery in which the eye's internal lens is emulsified with an ultrasonic handpiece and aspirated from the eye. Aspirated fluids are replaced with irrigation of balanced salt solution to maintain the anterior chamber.

Intraocular lens lens implanted in the eye to treat cataracts or myopia

Intraocular lens (IOL) is a lens implanted in the eye as part of a treatment for cataracts or myopia. The most common type of IOL is the pseudophakic IOL. These are implanted during cataract surgery, after the cloudy eye's natural lens has been removed. The pseudophakic IOL provides the same light focusing function as the natural crystalline lens. The second type of IOL, more commonly known as a phakic intraocular lens (PIOL), is a lens which is placed over the existing natural lens and is used in refractive surgery to change the eye's optical power as a treatment for myopia (nearsightedness).

Phakic intraocular lens

A phakic intraocular lens (PIOL) is a special kind of intraocular lens that is implanted surgically into the eye to correct myopia (nearsightedness). It is called "phakic" because the eye's natural lens is left untouched. Intraocular lenses that are implanted into eyes after the eye's natural lens has been removed during cataract surgery are known as pseudophakic.

Ectopia lentis disorder of lens

Ectopia lentis is a displacement or malposition of the eye's crystalline lens from its normal location. A partial dislocation of a lens is termed lens subluxation or subluxated lens; a complete dislocation of a lens is termed lens luxation or luxated lens.

James Benjamin Martel is a physician, surgeon and scientist. He is former Chair of Surgery, Mercy San Juan Medical Center, former Chief of Ophthalmology, Otolaryngology (ENT), and Plastic Surgery, Sutter Roseville Medical Center. He is the former Director of Ophthalmology, Sutter General and Memorial Hospitals and Assistant Professor of Ophthalmology and Radiology, Johns Hopkins Medical School and Wilmer Ophthalmological Institute. He is currently Clinical Professor of Ophthalmology and Associate Dean of Graduate Medical Education in California Northstate University College of Medicine.

Pseudoexfoliation syndrome, often abbreviated as PEX and sometimes as PES or PXS, is an aging-related systemic disease manifesting itself primarily in the eyes which is characterized by the accumulation of microscopic granular amyloid-like protein fibers. Its cause is unknown, although there is speculation that there may be a genetic basis. It is more prevalent in women than men, and in persons past the age of seventy. Its prevalence in different human populations varies; for example, it is prevalent in Scandinavia. The buildup of protein clumps can block normal drainage of the eye fluid called the aqueous humor and can cause, in turn, a buildup of pressure leading to glaucoma and loss of vision. As worldwide populations become older because of shifts in demography, PEX may become a matter of greater concern.

Howard V. Gimbel FRCSC, AOE, FACS, CABES, is a Canadian ophthalmologist, university professor, senior editor, and amateur musician. He is better known for his invention, along with Thomas Neuhann, of the continuous curvilinear capsulorhexis (CCC), a technique employed in modern cataract surgery.

Capsulotomy

Capsulotomy is a type of eye surgery in which an incision is made into the capsule of the crystalline lens of the eye. In modern cataract operations, the lens capsule is usually not removed. The most common forms of cataract surgery remove nearly all of the crystalline lens but do not remove the crystalline lens capsule. The crystalline lens capsule is retained and used to contain and position the intraocular lens implant (IOL).

Vitreomacular adhesion Human medical condition

Vitreomacular adhesion (VMA) is a human medical condition where the vitreous gel of the human eye adheres to the retina in an abnormally strong manner. As the eye ages, it is common for the vitreous to separate from the retina. But if this separation is not complete, i.e. there is still an adhesion, this can create pulling forces on the retina that may result in subsequent loss or distortion of vision. The adhesion in of itself is not dangerous, but the resulting pathological vitreomacular traction (VMT) can cause severe ocular damage.

IOL Scaffold or Intraocular lens Scaffold technique is a surgical procedure in Ophthalmology. In cases where the lens bag is ruptured and the cataract of the eye is not yet removed one can inject an artificial lens or Intraocular lens (IOL) inside the eye under the cataract. This way the IOL acts as a scaffold and prevents the cataract pieces from falling inside the eye. One can then remove the cataract pieces safely by emulsifying it with ultrasound. This technique is called IOL Scaffold and was started by Dr. Amar Agarwal from Chennai, India at Dr. Agarwal's Eye Hospital.

Burkhard Dick German university teacher

Burkhard Dick is a German ophthamologist who has specialized in refractive and cataract surgery. With his many contributions to the scientific literature on this topic, he is considered one of the pioneers of employing the femtosecond laser in cataract surgery. In the "Power List 2018" ranking of the world's most influential ophthalmologists by the publication The Ophthalmologist, Burkhard Dick was listed among the Top 20.

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