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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 one of the safest and most successful procedures in all of medicine.
The two main types of cataract extraction are intracapsular cataract extraction (ICCE) and extracapsular cataract extraction (ECCE).
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. There are two main types of extracapsular surgery: conventional ECCE and phacoemulsification. Conventional extracapsular cataract extraction involves manual expression of the lens through an incision made in the cornea or sclera. Although it requires a larger incision and the use of stitches, the conventional method is indicated for patients with very hard cataracts or lower counts of corneal endothelial cells. Phacoemulsification involves the use of a machine with an ultrasonic handpiece with a titanium or steel needle which vibrates at ultrasonic frequency under continuous irrigation to sculpt, chop and emulsify the cataract, thus making it easier to aspirate the fine particles. Irrigation-aspiration can then be performed with a bimanual system to clean out the cortical matter. Thereafter, a foldable Intraocular lens (IOL) made of Silicone or Acrylic materials of appropriate power is implanted using a holder/folder, or a proprietary insertion device provided along with the IOL. It is placed in the posterior chamber in-the-bag after cleaning out the cataract. Because a smaller incision is required, few or no stitches are needed and the patient's recovery time is usually shorter. Surgery Encyclopedia - Phacoemulsification for cataracts.
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 availableSurgery Encyclopedia - Extracapsular cataract extraction. Cryoextraction is a form of ICCE that freezes the lens with a cryogenic substance such as liquid nitrogenSurgery Encyclopedia - Cryotherapy for cataracts. 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 1980sMeadow, Norman B. Cryotherapy: A fall from grace, but not a crash. Ophthalmology Times. October, 15, 2005..
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 an extracapsular surgery, the surgeon performs an anterior capsulotomy, or capsulorhexis, to create an opening through which the lens nucleus can be removed and the intraocular lens implant inserted. An opacification or clouding of the posterior lens capsule frequently occurs in those who have had an extracapsular cataract extraction procedure, therefore, a laser posterior capsulotomy, or YAG laser capsulotomy, is used to clear the back implant surface Surgery Encyclopedia - Laser posterior capsulotomy. (Whereas a capsulotomy is the creation of an opening in the lens capsule, a capsulectomy is the acutal removal of lens capsule tissue.)
Cataract operations are mostly performed under a local anaesthetic and the patient will be allowed to go home the same day. Complications after cataract surgery are uncommon. Many people (up to 50%) can develop a posterior capsular opacification after initial cataract surgery. This is a thickening and clouding of the lens capsule (which was left behind when the cataract was removed) and it can be easily corrected using a Nd-Yag laser to make holes in the capsule for the person to see through. Retinal detachment is an uncommon complication of cataract surgery.
Previously, polymethylmethacrylate was used as the lens material, since it was discovered by Sir Harold Ridley in UK. He observed that the Royal Airforce pilots sustained eye injuries with splinters of glass from fighter plane windshield (made of PMMA). However, the eyes did not show any foreign body reaction. Thus the material was inert and useful for implantation in the eye. Sir Harold Ridley was the first to design and implant Intraocular lenses, which were further refined by using lathe cutting machines. Advances in technology have brought about the use of silicone and acrylic both of which are soft foldable inert material. This allows the lens to be folded and inserted into the eye through a smaller incision. Polymethyl methacrylate (PMMA) and Acrylic lenses can also be used with small incisions and are a better choice in people who have a history of uveitis, have diabetic retinopathy requiring vitrectomy with replacement by silicone oil or are at high risk of retinal detachment. Acrylic is not always an ideal choice due to its added expense. Latest advances include IOLs with square-edge design, non-glare edge design and yellow dye added to the IOL.
Couching was an early form of cataract surgery in which a small probe was inserted in the eye to push the lens down into the posterior chamber.
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.
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*.
See also
References
"Cataract surgery"