A cataract is a lens shadow in the eye that leads to decreased vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry views, light circles around the light, problems with bright light, and trouble seeing at night. This can cause difficulty driving, reading, or recognizing faces. Poor vision caused by cataracts can also lead to an increased risk of falling and depression. Cataracts cause half of all cases of blindness and 33% of vision problems worldwide.
Cataracts are most often due to aging but may also occur due to trauma or radiation exposure, present from birth, or occur after eye surgery to other problems. Risk factors include diabetes, tobacco smoking, prolonged sun exposure, and alcohol. Neither the protein grove nor the yellow-brown pigment can be deposited on the lens which reduces light transmission to the retina at the back of the eye. Diagnosis is done by eye examination.
Prevention includes wearing sunglasses and not smoking. Early symptoms can be enhanced by eyeglasses. If this does not help, surgery to remove cloudy lenses and replace them with artificial lenses is the only effective treatment. Surgery is necessary only if cataracts cause problems and generally result in improved quality of life. Cataract surgery is not available in many countries, which is especially true for women, those living in rural areas, and those who do not know how to read.
About 20 million people are blind because of cataracts. This is the cause of about 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 developing countries, and 1 to 4 per 100,000 children in developed countries. Cataracts are becoming more common with age. More than half of people in the United States suffer from cataracts at age 80.
Video Cataract
Signs and symptoms
The signs and symptoms vary depending on the type of cataract, although there is considerable overlap. People with sclerotic or brunescent nuclear cataracts often see vision reduction. Those with posterior subcapsular catarres usually complain of glare as their primary symptom.
The severity of cataract formation, assuming no other eye diseases are present, is judged primarily by visual acuity tests. Other symptoms include frequent change of glasses and colored halos due to lens hydration.
Maps Cataract
Cause
Age
Age is the most common cause. The lens proteins change shape and decrease over time, and this process is accelerated by diseases such as diabetes mellitus and hypertension. Environmental factors, including toxins, radiation, and ultraviolet light, have a cumulative effect, exacerbated by the loss of protective and restorative mechanisms due to changes in gene expression and chemical processes within the eye.
Trauma
Blunt trauma causes swelling, thickening, and whitening of lens fibers. While the swelling usually disappears over time, the white color may still exist. In severe blunt trauma, or injuries that penetrate the eye, the capsule where the sitting lens can be damaged. This damage allows the liquid from other parts of the eye to quickly enter the lens leading to swelling and then whiten, blocking the light from reaching the retina at the back of the eye. Cataracts can occur in 0.7 to 8.0% of cases after an electrical injury. Blunt trauma can also cause cataracts or star-shaped petals.
Radiation
Cataracts can appear as the effect of exposure to different types of radiation. X-rays, one form of ionizing radiation, can damage the DNA of lens cells. Ultraviolet light, particularly UVB, has also been shown to cause cataracts, and some evidence suggests that sunglasses worn at an early age may slow its progression in the future. Microwaves, a type of nonionized radiation, can cause damage by denaturing protective enzymes (eg, glutathione peroxidase), by oxidizing the thiol group of proteins (causing protein aggregation), or by damaging lens cells through thermoelastic expansion. Coagulation of proteins caused by electrical injury and heat whitens the lens. This same process makes the egg albumen white and opaque during cooking.
Genetics
The genetic component is strong in cataract development, most often through mechanisms that protect and maintain the lens. The presence of cataracts in childhood or early life can sometimes be caused by certain syndromes. Examples of chromosomal abnormalities associated with cataracts include 1q21.1 removal syndrome, cri-du-chat syndrome, Down syndrome, Patau syndrome, trisomy 18 (Edward syndrome), and Turner syndrome, and in the case of type 2 neurofibromatosis, juvenile cataracts in one or both sides can be recorded. Examples of single gene disorders include Alport syndrome, Conradi syndrome, cerebrotendineous xanthomatosis, myotonic dystrophy, and oculocerebrorenal syndrome or Lowe syndrome.
Skin diseases
Skin and lens have the same embryological origins that can be affected by similar diseases. Those with atopic dermatitis and eczema sometimes develop cataracts in cataracts. Ichthyosis is an autosomal recessive disorder associated with cuneiform cataract and nuclear sclerosis. Nevus and pemphigus basal cells have similar associations.
Smoking and alcohol
Cigarette smoking has been shown to double the rate of nuclear sclerotic cataract and triple the rate of posterior subcapsular cataracts. The evidence is contrary to the effects of alcohol. Some surveys show links, but others follow people who are not longer.
Vitamin C is not enough
Low vitamin C intake and serum levels have been associated with higher rates of cataracts. However, the use of vitamin C supplements has not shown its benefits.
Drugs
Some drugs, such as systemic, topical, or inhaled corticosteroids, may increase the risk of developing cataracts. Corticosteroids most commonly cause posterior subcapsular cataracts. People with schizophrenia often have risk factors for lens opacities (such as diabetes, hypertension, and malnutrition) but antipsychotic drugs may not contribute to cataract formation. Miotics and triparanol may increase the risk.
Post operation
Virtually every person undergoing a vitrectomy - without ever undergoing cataract surgery - will experience development of nuclear sclerosis after surgery. This may be because genuine vitreous humor differs from the solution used to replace vitreous (a vitreous substitute), such as BSS Plus. This may also be because genuine vitreous humor contains ascorbic acid which helps neutralize oxidative damage to the lens and because traditional vitreous substitutes do not contain ascorbic acid. Thus, for phakic patients requiring vitrectomy, it is becoming increasingly common for ophthalmologists to offer vitrectomy with combined prophylactic cataract surgery procedures to prophylactically prevent cataract formation.
Other diseases
Diagnosis
Classification
Cataracts may be partial or complete, stationary or progressive, or hard or soft. The main types of age-related cataracts are nuclear, cortical, and posterior subcapsular sclerosis.
Nuclear sclerosis is the most common type of cataract, and involves a central or 'nuclear' lens. This eventually becomes hard, or 'sclerotic', due to condensation on the lens nuclei and the deposition of the brown pigment inside the lens. In the later stages is called brunescent cataract. Cataracts of this type may present with a shift to farsightedness, causing problems with remote vision even though reading is less affected.
Cortical cataract is due to the lens cortex (outer layer) becomes opaque. They occur when a change in the fluid contained on the edge of the lens causes fissuring. When the cataract is seen through the ophthalmoscope, or other enlargement system, its appearance is similar to the white spokes of the wheel. Symptoms often include problems with glare and light scatter at night.
The posterior subcapsular cataract is cloudy on the back of the lens adjacent to the capsule (or bag) where the lens sits. As light becomes more focused on the back of the lens, they can cause symptoms that are not proportional to their size.
An immature cataract has several transparent proteins, but with ripe cataracts, all lens proteins are blurred. In hypermatures or Morgagnia cataracts, the lens proteins become liquid. Congenital cataracts, which can be detected in adulthood, have different classifications and include lamellar, polar, and sutural cataracts.
Cataracts can be classified using the LOCS III lens opacity classification system. In this system, cataracts are classified by type as nuclear, cortical, or posterior. Cataracts are further classified based on severity on a scale from 1 to 5. The LOCS III system is highly reproducible.
Prevention
Risk factors such as UVB exposure and smoking can be overcome. Although there is no way to prevent cataracts from being scientifically proven, wearing sunglasses that counteract ultraviolet light can slow its development. While adequate antioxidant intake (such as vitamins A, C, and E) has been considered to protect against cataract risk, clinical trials show no benefit from supplements; although the evidence is mixed, but weakly positive, for the potential protective effects of nutrients lutein and zeaxanthin. The use of statins is somewhat associated with a lower risk of sclerotic cataracts.
Treatment
Surgery
Operability feasibility depends on the functional and visual needs of a particular person and other risk factors. Cataract removal can be done at any stage and no longer requires lens maturation. Surgery is usually 'outpatient' and performed using local anesthesia. About 9 out of 10 patients can achieve a corrected vision of 20/40 or better after surgery.
Some recent evaluations found that cataract surgery can meet expectations only when significant functional impairment because cataracts exist prior to surgery. Approximate visual functions such as VF-14 have been found to provide more realistic estimates than visual acuity testing alone. In some developed countries, the tendency to overuse cataract surgery has been noted, which can lead to disappointing results.
Facoemulsification is the most widely used cataract surgery in developed countries. This procedure uses ultrasonic energy to emulsify cataract lenses. Phacoemulsification usually consists of six steps:
- Anesthesia - Eyes numb with subtenon injection around the eyes (see: retrobulbar block) or topical anesthetic eye drops. The first also provides eye muscle paralysis.
- Corneal incision - Two wounds are made at the edge of the cornea clear to allow insertion of the instrument into the eye.
- Capsulorhexis - A needle or small pair of forceps is used to create a circular hole in the capsule where the lens sits.
- Phacoemulsification - A handheld ultrasonic probe is used to break down and emulsify a lens into a liquid using ultrasound wave energy. The resulting 'emulsion' is sucked.
- Irrigation and aspiration - The cortex, which is the soft outer layer of cataracts, is aspirated or aspirated. The discharged liquid is constantly replaced by saline solution to prevent the collapse of anterior chamber structures (the front of the eye).
- Lens insertion - Foldable plastic lens inserted into a capsular pouch previously containing a natural lens. Some surgeons also inject antibiotics into the eye to reduce the risk of infection. The final step is to inject salt water into the corneal wound to cause the area to swell and close the incision.
Extracapsular cataract extraction (ECCE) consists of removing the lens manually, but leaving most of the capsule intact. The lens is expressed through a 10 to 12 mm incision covered with stitches at the end of the operation. ECCE is less common than phacoemulsification, but can be useful when dealing with very loud 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 an automatic scleral sealing wound in the sclera which, ideally, is watertight and does not require suturing. Although "small", the incision is still much larger than the portal in phacoemulsion. This operation is increasingly popular in developing countries where access to phacoemulsification is still limited.
Intracapsular cataract extraction (ICCE) is rare. The surrounding lenses and capsules are removed intact through a large incision while pressure is applied to the vitreous membrane. Surgery has high complication rates.
Prognosis
Postoperative care
The postoperative recovery period (after removing the cataract) is usually short. Patients usually take outpatient on the day of surgery, but are advised to move with caution and avoid tension or heavy lifting for about a month. The eye is usually patched on the day of surgery and the use of eye protection at night is often recommended for several days after surgery.
In all types of surgery, the cataract lens is removed and replaced with an artificial lens, known as an intraocular lens, which remains in the eye permanently. Intraocular lenses are usually monofocal, correcting for either distance or near vision. Multifocal lenses can be implanted to improve near vision and distance simultaneously, but this lens may increase the likelihood of unsatisfactory vision.
Complications
Serious complications from cataract surgery include retinal release and endophthalmitis. In both cases, the patient sees a sudden drop in vision. In endophthalmitis, patients often describe pain. Retinal detachment often presents with a visually impaired visual field, blurring vision, flashes of light, or floating spots.
The risk of retinal detachment is estimated to be about 0.4% in 5.5 years, corresponding to a 2.3-fold increase in risk compared with expected incidence naturally, with older studies reporting much higher risk. These incidents increase over time in a somewhat linear fashion, and the increased risk lasts at least 20 years after the procedure. Specific risk factors are younger age, male gender, longer axis length, and complications during surgery. In the group of patients with the highest risk, the incidence of pseudofakia retinal detachment can reach 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 in the front of the eye in corneal or back edema of the eye in cystoid macular edema. They are usually the result of excessive inflammation after surgery, and in both cases, the patient may see blurred, foggy vision. They usually improve with time and with the application of anti-inflammatory drops. The good risk is about one in 100. It is unclear whether NSAIDs or corticosteroids are superior in reducing postoperative inflammation.
Posterior capsular opacity, also known as after-cataract, is a condition in which months or years after cataract surgery succeed, vision deteriorates or problems with glare and repeated scattering of light, usually due to the thickening of the back or posterior capsule surrounding the embedded lens called 'posterior lens capsule opacity'. The growth of the natural lens cell remaining after the natural lens is removed may be the cause, and the younger the patient, the greater the chance of this occurrence. Management involves cutting a small, circular area in the posterior capsule with a targeted beam of energy from a laser, called Nd: YAG laser capsulotomy, after which type of laser is used. The laser can be very accurately directed, and a small part of the capsule is cut down without harm to the bottom of the inside of the eye. This procedure leaves enough capsules to hold the lens in place, but is sufficient to allow light to enter directly into the retina. Serious side effects are rare. Posterior capsular opacity occurs and occurs in up to one in four operations, but this number decreases after the introduction of modern intraocular lenses along with a better understanding of the cause.
Vitreous touch syndrome is a possible complication of intracapsular cataract extraction.
Epidemiology
Age-related cataracts are responsible for 51% of the world's blindness, about 20 million people. Globally, cataracts cause moderate to severe defects 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 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 wait, and barriers to, operations, such as costs, 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 of 65 and 74, and 91% between the ages of 75 and 85. Cataract affects nearly 22 million Americans age 40 and older. By age 80, more than half of 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 more than 51% of blindness. Access to eye care in many countries in this region is limited. Children related cataracts are responsible for 5-20% of blindness in childhood of the world.
History
The first reference to cataracts and their treatment in Ancient Rome was found at 29 AD in De Medicinae , the work of the Latin encyclopedia Aulus Cornelius Celsus. Archaeological evidence of eye surgery in the Roman era also exists.
Galen Pergamon (circa 2nd century AD), a prominent Greek physician, surgeon and philosopher, performed an operation similar to that of modern cataract surgery. Using a needle-shaped tool, Galen attempted to remove the cataract's eye lens.
Cataract surgery is described by Indian doctors, Su? Ruta (about 200 AD).
The Muslim eye doctor Ammar Al-Mawsili, in his book of Choice of Eye Diseases, was written about 1,000, wrote his findings on syringes and cataract extraction techniques while experimenting with it in a patient.
Etymology
"Cataract" comes from the Latin cataracta , meaning "waterfall", and from Ancient Greek ?????????? ( katarrhakt? s ), "down-rushing", from ???? ????? ( katarass? ) which means "to run down" (from the word -, "down"; arassein , "to attack, run"). Because the rapidly flowing water turns white, the term may have been used metaphorically to describe the appearance of a mature ocular opacity. In Latin, cataracta has an alternative meaning "portcullis" and the name may pass through French to form English meaning "eye disease" (early in the 15th century), on the idea of ​​"obstruction". The early Persian physician called the term nazul-i-ah , or "water descent" - the vulgaris became a waterfall or cataract disease - believing such blindness was caused by the outpouring of corrupt humor into the eye.
Research
The droplet of N-Acetylcarnosine has been studied as a medical treatment for cataracts. Drops are believed to work by reducing oxidation and gum damage to the lens, in particular reducing the crystal cross linking. Several benefits have been demonstrated in randomized controlled trials sponsored by small producers but further independent verification is still required.
Femtosecond laser mode locking, used during cataract surgery, was originally used to cut accurate and predictable flaps in LASIK surgery, and has been introduced in cataract surgery. The incisions at the intersection of sclera and cornea and holes in the capsule during capsulorhexis, traditionally made with hand-knives, needles, and pliers, depend on the skill and experience of the surgeon. Sophisticated three-dimensional images of the eye can be used to guide the laser to make this incision. Nd: YAG laser can also break up cataracts as in phacoemulsification.
Stem cells have been used in clinical trials for lens regeneration in twelve children under two years of age with cataracts present at birth. The children are followed for six months, so it is not known what the long-term outcomes are, and it is unknown whether this procedure will work in adults.
See also
- Galactosemic Cataracts
References
External links
- Cataracts at Curlie (based on DMOZ)
- Pictures of different types of cataracts
- Videos depicting history and science look at your own eyes on YouTube
Source of the article : Wikipedia
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