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Cataract surgery is the removal of the lens of the eye (also called "crystalline") that has developed an opacification, which is referred to as a cataract. Metabolic changes of the crystalline lens fibers over the time lead to the development of the cataract and loss of transparency. Following surgical removal of the natural lens, an artificial intraocular lens implant is inserted (eye surgeons say that the lens is "implanted"). Cataract surgery is generally performed by an ophthalmologist (eye surgeon) at an ambulatory (rather than inpatient) setting, in a surgical center or hospital, using local anesthesia (either topical, peribulbar, or retrobulbar). Well over 90% of operations are successful in restoring useful vision, with a low complication rate.  Day care, high volume, minimally invasive, small incision phacoemulsification with quick post-op recovery has become the standard of care in cataract surgery all over the world.
Additional recommended knowledge
Currently, the two main types of cataract surgery extraction performed by the ophthalmologists are phacoemulsification (phaco) and conventional extracapsular cataract extraction (ECCE). In both types of surgery an Intraocular lens is usually inserted. Foldable lenses are generally used when phaco is performed while non-foldable lenses are placed following ECCE. The small incision size used in phacoemulsification often allows "sutureless" wound closure. ECCE usually require stitching.
Cataract extraction using intracapsular cataract extraction (ICCE) has been superseded by phaco & ECCE, and is only rarely performed.
Couching is a historical method of performing cataract surgery and it is reported to have been used in ancient Egypt. In this procedure, a small probe was inserted into the eye in order to push the lens down into the vitreous cavity. This would improve visual acuity by some degree, but the result was poor. No glasses were even known back in those days. We now know that the lens can spontaneously dislocate into the vitreous cavity in certain diseases including Marfan's Syndrome and Homocystinuria. The dislocations of the crystalline into the vitreous cavity may require surgical intervention to prevent the development of intra-ocular inflammation and increase of the intra-ocular pressure.
Types of surgery
Extracapsular cataract extraction involves the removal of the almost the entire natural lens while the elastic lens capsule (posterior capsule) is left intact to allow implantation of an intraocular lens. There are two main types of cataract surgery:
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.
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 surgical procedure in phacoemulsification for removal of cataract involves a number of steps. Each step must be carefully and skillfully performed in order to achieve the desired result. The steps may be described as follows:
The pupil is dilated using drops (if the IOL is to be placed behind the iris) to help better visualise the cataract. Pupil constricting drops are reserved for secondary implantation of the IOL in front of the iris (if the cataract has already been removed without primary IOL implantation). Anesthesia may be placed topically (eyedrops) or via injection next to (peribulbar) or behind (retrobulbar) the eye. Oral or intravenous sedation may also be used to reduce anxiety. General anesthesia is rarely necessary, but may be employed for children and adults with particular medical or psychiatric issues. The operation may occur on a stretcher or a reclining examination chair. The eyelids and surrounding skin will be swabbed with disinfectant. The face is covered with a cloth or sheet, with an opening for the operative eye. The eyelid is held open with a speculum to minimize blinking during surgery. Pain is usually minimal in properly anesthetised eyes, though a pressure sensation and discomfort from the bright operating microscope light is common. The ocular surface is kept moist using sterile saline eyedrops or methylcellulose viscoelatic. The incision is fashioned at or near where the cornea and sclera meet (limbus = corneoscleral junction). Advantages of the smaller incision include use of few or no stitches and shortened recovery time. . A capsulotomy (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 phacoemulsification, the surgeon performs an anterior continuous curvilinear capsulorhexis, to create a round and smooth opening through which the lens nucleus can be emulsified and the intraocular lens implant inserted.
Following cataract removal (via ECCE or phacoemulsification, as described above), an intraocular lens is usually inserted. After the IOL is inserted, the surgeon checks that the incision does not leak fluid. This is a very important step, since wound leakage increases the risk of unwanted microrganisms to gain access into the eye and predispose to endophathalmitis. An antibiotic/steroid combination eye drop is put and an eye shield may be applied on the operated eye, sometimes supplemented with an eye patch.
Most cataract operations are performed under a local anaesthetic, allowing the patient to go home the same day. The use of an eye patch may be indicated, usually for about some hours, after which the patient is instructed to started using the eyedrops to control the inflammation and the antibiotics that prevent infection.
Occasionally, a peripheral iridectomy may be performed to minimize the risk of pupillary block glaucoma. An opening through the iris can be fashioned manually (surgical iridectomy) or with a laser (called YAG-laser iridotomy). The laser peripheral iridotomy may be performed either prior to or following cataract surgery.
The iridectomy hole is larger when done manually than when performed with a laser. When the manual surgical procedure is performed, some negative side effects may occur, such as that the opening of the iris can be seen by others (aesthetics), and the light can fall into the eye through the new hole, creating some visual disturbances . In the case of visual disturbances, the eye and brain often learn to compensate and ignore the disturbances over a couple of months. Sometimes the peripheral iris opening can heal, which means that the hole ceases to exist. This is the reason why the surgeon sometimes makes two holes, so that at least one hole is kept open.
After the surgery, the patient is instructed to use anti-inflammatory and antibiotic eye drops for up to two weeks (*depending on the inflammation status of the eye and some other variables). The eye surgeon will judge, based on each patient's idiosyncrasies, the time length to use the eye drops. The eye will be pretty recovered within a week, and complete recovery should be expected in about a month. The patient should not participate in contact/extreme sports until cleared to do so by the eye surgeon.
Complications after cataract surgery are relatively uncommon.
The earliest references to cataract surgery are found in Sanskrit manuscripts dating from the 5th century BC, which show that Sushruta developed specialised instruments and performed the earliest eye surgery in India. 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.
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 ancient times and continued to be used throughout the Middle Ages - However, it has now been replaced by extracapsular cataract surgery and, specially, phacoemulsification.
In 1748, Jacques Daviel started with modern cataract surgery, in which the cataract is actually extracted from the eye. In the 1940s Harold Ridley introduced the concept of implantation of the intraocular lens which permitted more efficient and comfortable visual rehabilitation possible after cataract surgery. The implantation of foldable intraocular lens is the procedure considered the state-of-the-art.
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 method of surgery decreased the need for an extended hospital stay and made the surgery ambulatorial. Patients that undergo cataract surgery hardly complain of pain or even disconfort during the procedure. However, patients that have topical anesthesia (as compared to those that have peribulbar block anesthesia) may experience some degree of discomfort.
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 .
In India, modern surgery with intraocular lens insertion in Government and Non Government Organisation (NGO) sponsored Eye Surgical Camps have replaced older surgical procedures.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Cataract_surgery". A list of authors is available in Wikipedia.|