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Cataract surgery is the removal of the lens of the eye that has developed a cataract. The natural lens is then replaced with an artificial intraocular lens. It is generally regarded as one of the safest types of surgery, and although complications can occur, over 90% of operations are successful in restoring useful vision.
Types Currently, the two main types of cataract extraction performed by ophthalmologists are conventional extracapsular cataract extraction (ECCE) and phacoemulsification (phaco). Extracapsular cataract extraction Extracapsular cataract extraction involves the removal of the lens while the elastic lens capsule is left partially intact to allow implantation of an intraocular lens. Intracapsular cataract extraction Intracapsular cataract extraction (ICCE) involves the removal of the lens and the surrounding lens capsule in one piece. The lens is then replaced with an artificial plastic lens (an intraocular lens implant) of appropriate power which remains permanently in the eye. The procedure has a relatively high rate of complications due to the large incision required and pressure placed on the vitreous body, thus is rarely performed in countries where operating microscopes and high-technology equipment are readily available. Cryoextraction is a form of ICCE that freezes the lens with a cryogenic substance such as liquid nitrogen. Although it is now used primarily for the removal of subluxated lenses, it was the favored form of cataract extraction from the late 1960s to the early 1980s. Operation procedures Surgical procedure in phacoemulsification for removal of cataract involves a number of steps, in order: starting with proper anaesthesia, exposure using a lid speculum, incision (corneal or scleral), viscoelastic injection to stabilise the anterior chamber, capsulotomy, hydrodissection, hydrodelineation, ultrasonic emulsification, nuclear chopping, cortical aspiration, capsular polishing, implantation & centration of IOL, viscoelastic removal, wound closure / hydration and finally a subconjunctival injection of antibiotic/steroid mix. A capsulotomy/capsulorhexis, rarely known as cystitomy, is a procedure to open a portion of the lens capsule. An anterior capsulotomy refers to the opening of the front portion of the lens capsule, whereas a posterior capsulotomy refers to the opening of the back portion of the lens capsule. In an extracapsular surgery, the surgeon performs an anterior continuous curvilinear capsulorhexis, to create an opening through which the lens nucleus can be emulsified and the intraocular lens implant inserted. As the cataract operations are mostly performed under a local anaesthetic and the patient will be allowed to go home the same day. An eye examination or pre-operative evaluation by an eye surgeon is necessary to confirm the presence of a cataract and to determine if the patient is a suitable candidate for surgery. The patient must fulfill certain requirements, such as: The routine PC-IOLs are available with the surgical suite or doctor's office and surgery can be performed without delay once the patient is cleared for surgery. The patient will receive pupil dilating drops (if the lens is to be fitted behind the iris), to help better visualise the cataract. Pupil constricting drops are reserved for secondary AC-IOL implantation (if the cataract has already been removed and an anterior chamber IOL is to be fitted in front of the iris). The patient will also get local anesthetics in the eye, and tranquillizing medicines, if desired. Once the medicines have taken effect, the patient will enter the operating room and be seated in a chair which reclines like a dentist's chair, and the eyelids, and surrounding skin will be swabbed with disinfectant. The face will be covered with a cloth, with a hole for the eyes. The eye will be held open with a speculum so that the patient cannot blink during the surgery. No pain is usually felt during the procedure, apart from a pressure sensation in properly anesthetised eyes and the only discomfort is from the bright light from the microscope that the surgeon uses. The nurse sprays the eye with a sterile saline solution, so the eye does not dry. The surgeon starts by making the incisions that he/she may need, and then the actual surgery is begun. Phacoemulsification is done and cataract is removed. The insertion of the PC-IOL is done using an unenlarged incision for foldable IOLs. After the lens is inserted, the surgeon checks that the incisions do not leak fluid, and a conjunctival injection of steroid-antibiotic is given. An ointment, eye shield and bandage is applied on the operated eye. In some cases, an "emergency release valve" (peripheral iridectomy) can be made at the same time by making one large or two smaller holes in the iris, in case the pupil is blocked, in order to avoid glaucoma. This can be done in two ways: either surgically by first lifting up the front layer of the iris and cut away a small portion, and then make a small hole in the pigment/back layer of the with a suction device - called iridectomy. The other alternative is with a laser a couple of weeks before the lens surgery - called laser peripheral iridotomy. The iridectomy hole is larger when done surgically, and some of the negative effect are that it can be seen by others (aesthetics), and that light can fall into the eye through the new hole creating visual disturbances (blurry images on top of the normal view). In the case of visual disturbances, the eye and brain often learns to compensate and ignore the disturbances over the couple of months. One negative effect with laser peripheral iridotomy is that the hole can heal, which means that the hole ceases to exist, meaning there is no "emergency release valve". Therefore, the surgeon often makes two holes, so that at least one hole is open. Afterwards, the patient will be instructed to keep the eyes clean, and avoid infectious environments (such as saunas, swimming pools), and to take eye drops - anti-inflammatory and antibiotics for the time it takes the eye to heal completely. The eye will be mostly recovered within a week, and complete recovery should be expected in about three weeks. The patient must not lift heavy things, do anything that elevates the blood pressure. Also, the patient should avoid contact/extreme sports within the next several months. Special types of Phakic IOLs (PIOLs) are available in patiens requiring IOL implantation without removal of crysalline human lens, particularly useful in refractive surgery for high myopia. For this, the eye surgeon has to decides the size of the PIOL. If the lens is of incorrect length, then it can rotate inside the eye, causing astigmatism, and/or damage to the natural lens. It can also block the natural flow of fluid inside the eye, causing glaucoma. The size is usually estimated, by measuring white-to-white, and estimating the ciliary sulcus diameter. However, the surgeon can perform 3D ultrasound biomicroscopy with for example Artemis for a completely accurate measurement. 3D ultrasound is to traditional 2D ultrasound like computer assisted tomography is to x-ray. Therefore, 3D ultrasound examination is strongly recommended, since the white-to-white guesstimate does not have a strong correlation with sulcus-to-sulcus - neither for myopic, nor for hyperopic. About 1% of sulcus-to-sulcus estimates based on white-to-white are so wrong that serious complications can arise. This type of phakic lens has to be ordered from the manufacturer, requiring a number of weeks before the surgery. However, on the other hand, the routine posterior chamber IOLs (PC-IOLs) used for routine cataract surgical cases are available with the surgical suite or doctor's office and the cataract surgery can usually be performed without delay once the patient is cleared for surgery. Complications
History The earliest references to cataract surgery are found in Sanskrit manuscripts dating from the 5th century BC, which show that Susruta in India developed specialised instruments and performed the earliest eye surgery. In the Western world, bronze instruments that could have been used for cataract surgery, have been found in excavations in Babylonia, Greece and Egypt. The first references to cataract and its treatment in the West are found in 29 AD in De Medicinae, the work of the Latin encyclopedist Aulus Cornelius Celsus. In 1748, Jacques Daviel started with modern cataract surgery, in which the cataract is actually extracted from the eye. In the 1940s Harold Ridley invented the intraocular lens which made efficient and comfortable visual rehabilitation possible after cataract surgery. In 1967, Charles Kelman introduced phacoemulsification, a technique that uses ultrasonic waves to emulsify the nucleus of the crystalline lens in order to remove the cataracts without a large incision. This new surgery removed the need for an extended hospital stay and made the surgery less painful. According to surveys of members of the American Society of Cataract and Refractive Surgery, approximately 2.85 million cataracts procedures were performed in the United States during 2004 and 2.79 million in 2005 . The first extracapsular cataract surgery using a sharply pointed instrument with a handle fashioned into a trough was described in Susrutasamhita. This technique is known to have existed in India as described and performed by Susruta sometime in early BC. Another early technique to remove cataracts was couching, which involved using a thin needle or stick to remove the clouding. This technique is known to have existed in Roman times and continued to be used throughout the Middle Ages - it has now been superseded by extracapsular cataract surgery. In India, modern surgery with intraocular lens insertion in Government and Non Government Organisation (NGO) sponsored Eye Surgical Camps have replaced obsolete surgical procedures. See also | ||||||||||
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