Extracapsular Cataract Extrac... Health Article

Definition

Extracapsular cataract extraction (ECCE) is a category of eye surgery in which the lens of the eye is removed while the elastic capsule that covers the lens is left partially intact to allow implantation of an intraocular lens (IOL). This approach is contrasted with intracapsular cataract extraction (ICCE), an older procedure in which the surgeon removed the complete lens within its capsule and left the eye aphakic (without a lens). The patient's vision was corrected after intracapsular extraction by extremely thick eyeglasses or by contact lenses.

There are two major types of ECCE: manual expression, in which the lens is removed through an incision made in the cornea or the sclera of the eye; and phacoemulsification, in which the lens is broken into fragments inside the capsule by ultrasound energy and removed by aspiration.

Historical background

The purpose of ECCE is to restore clear vision by removing a clouded or discolored lens and replacing it with an IOL. Cataract operations are among the oldest recorded surgical procedures; there are references to cataract surgery in the Code of Hammurabi in 1750 B.C. and in the treatises written around 600 B.C. by Susruta, a famous surgeon from India. In the ancient world, lenses damaged by cataracts were dislocated rather than removed in the strict sense; the surgeon used a lance to push the clouded lens backward into the vitreous body of the eye. This operation, known as couching, was standard practice until the mid-eighteenth century. Couching is still performed by some traditional healers in Africa and parts of Asia.

The first extracapsular extraction of a cataract was performed by a French surgeon named Jacques Daviel in 1753. Daviel removed the lens through a fairly long incision in the cornea of the eye. In 1865, the German ophthalmologist Albrecht von Graefe refined the operation by removing the lens through a much smaller linear incision in the sclera of the eye. After von Graefe, however, intracapsular extraction gradually became the favored method of cataract removal even though it left the patient without a lens inside the eye. The two inventions that made extracapsular extraction preferable again were the operating microscope and the intraocular lens. The first eye surgery performed with an operating microscope was done in Portland, Oregon, in 1948; in the same year, a British ophthalmologist named Harold Ridley implanted the first IOL in the eye of a cataract patient. Between 1948 and the 1980s, manual expression was the standard form of ECCE. Although phacoemulsification was first introduced in 1967, it was not widely accepted at first because it requires special techniques that take time for the surgeon to learn as well as expensive specialized equipment. As of 2003, phacoemulsification is now performed more often in the United States and Europe than "standard" ECCE. The manual expression technique, however, is still widely used in developing countries with large numbers of patients with eye disorders and limited hospital budgets.

The lens and cataract formation

To understand cataract surgery, it is helpful to have a basic description of the structure of the lens in the human eye. The lens, which is sometimes called the crystalline lens because it is transparent, is located immediately behind the iris. In humans, the lens is about 9 mm long and 4 mm wide. It consists of protein fibers and water, with the fibers arranged in a pattern that allows light to pass through the lens. There are three layers of cells in the lens: a central nucleus, which becomes denser and harder as a person ages; a cortex surrounding the nucleus, which contains cells that are metabolically active and continue to grow and divide; and a layer of cells between the cortex and the lens capsule known as the subcapsular epithelium.

Although a few people are born with cataracts or develop them in childhood, most cataracts are the result of the aging process. As people grow older, the protein fibers in the lens become denser, start to clump together, and form cloudy or opaque areas in the lens. Cataracts vary considerably in their speed of progression; they may develop in a few months or over a period of many years. Some people have cataracts that stop growing at an early stage of development and do not interfere with their vision. Although most people develop cataracts in both eyes, they do not usually progress at the same rate, so that the person has much better vision in one eye than in the other.

Ophthalmologists classify cataracts according to their location in the lens. It is possible for a person to have more than one type of cataract.

• Nuclear cataracts. Nuclear cataracts grow slowly over many years but can become very large and hard, which complicates their removal. They are sometimes called brunescent cataracts because they are characterized by deposits of brown pigment that give the lens an amber color. Nuclear cataracts are most commonly associated with age and with smoking as risk factors.
• Cortical cataracts. Cataracts in the cortex of the lens develop more rapidly than nuclear cataracts but remain softer and are easier to remove. They are thought to be caused by an increase in the water content of the lens. Risk factors for cortical cataracts include female sex and African or Caribbean heritage.
• Posterior subcapsular (PSC) cataracts. This type of cataract, which develops between the back of the lens and the lens capsule, is the softest and most rapidly growing type. PSC cataracts tend to scatter light at night and thus interfere with nighttime driving. Risk factors for PSC cataracts include diabetes and a history of treatment with steroid medications.