PHACOEMULSIFICATION FOR CATARACTS
Category: Ophthalmology
Abstract : Phacoemulsification for cataracts : Phacoemulsification cataract surgery is a procedure in which an ultrasonic device is used to break up and then remove a cloudy lens, or cataract, from the eye to improve vision. The insertion of an intraocular lens (IOL) usually immediately follows phacoemulsification. Phacoemulsification, or phaco, as surgeons refer to it, is used to restore vision in patients
Phacoemulsification for cataracts : Phacoemulsification cataract surgery is a procedure in which an ultrasonic device is used to break up and then remove a cloudy lens, or cataract, from the eye to improve vision. The insertion of an intraocular lens (IOL) usually immediately follows phacoemulsification. Phacoemulsification, or phaco, as surgeons refer to it, is used to restore vision in patients whose vision has become cloudy from cataracts.
In the first stages of a cataract, people may notice only a slight cloudiness as it affects only a small part of the lens, the part of the eye that focuses light on the retina. As the cataract grows, it blocks more light and vision becomes cloudier. As vision worsens, the surgeon will recommend cataract surgery, usually phaco, to restore clear vision. With advancements in cataract surgery such as the IOL patients can sometimes experience dramatic vision improvement.
As people age, cataracts are likely to form. The National Eye Institute (NEI) reports in a 2002 study that more than half of all United States residents 65 and older have a cataract. People who smoke are at a higher risk for cataracts. Increased exposure to sunlight without eye protection may also be a cause.
Cataracts also can occur anytime because of injury, exposure to toxins, or diseases such as diabetes. Congenital cataracts are caused by genetic defects or developmental problems, or exposure to some contagious diseases during pregnancy.
However, the most common form of cataract in the United States is age related. According to the NEI, cataracts are more common in women than in men, and Caucasians have cataracts more frequently than other races, especially as people age. People who live close to the equator also are at higher risk for cataracts because of increased sunlight exposure.
More than 1.5 million cataract surgeries are performed in the United States each year. The NEI reports that the federal government, through Medicare, spends more than $3.4 billion each year treating cataracts. Cataract surgery is one of the most common surgeries performed, and also one of the safest and most effective. Phaco is currently the most popular version of cataract surgery.
Phacoemulsification is a variation of extracapsular cataract extraction, a procedure in which the lens and the front portion of the capsule are removed. Formerly the most popular cataract surgery, the older method of extracapsular extraction involves a longer incision, about 0.4 in (10 mm), or almost half of the eye. Recovery from the larger incision extracapsular extraction also requires almost a week-long hospital stay after surgery, and limited physical activity for weeks or even months.
Charles Kelman created phacoemulsification in the late 1960s. His goal was to remove the cataract with a smaller incision, less pain, and shorter recovery time. He discovered that the cataract could be broken up, or emulsified, into small pieces using an ultrasound tip. At first, phaco was slow to catch on because of its high learning curve. With its success rate and shorter recovery period, surgeons slowly learned the technique. Over the past decades, surgeons have constantly refined phaco to make it even safer and more successful. Innovations in technology such as the foldable IOL also have helped improve outcomes by allowing surgeons to make smaller incisions.
During surgery, the patient will probably breathe through an oxygen tube because it might be difficult to surbreathe with the draping. The patient’s blood pressure and heart rate also are likely to be monitored. Before making the incision, the surgeon inserts a long needle, usually through the lower eyelid, to anesthetize the area behind the eyeball. The surgeon then puts pressure on the eyeball with his or her hand or a weight to see if there is any bleeding (possibly caused by inserting the anesthetic). The pressure will stop this bleeding. This force also decreases intraocular pressure, which lowers the chances of complications.
After applying the pressure, the surgeon looks through a microscope and makes an incision about 0.1 in (3 mm) on the side of the anesthetized cornea. As of 2003, surgeons are beginning to favor the temporal location for the incision because it has proved to be safer. The incision site also varies depending on the size and denseness of the cataract. Once the incision is made, a viscoelastic fluid is injected to reduce shock to the intraocular tissues. The surgeon then makes a microscopic circular incision in the membrane that surrounds the cataract; this part of the procedure is called capsulorhexis.
A water stream then frees the cataract from the cortex. The surgeon inserts a small titanium needle, or phaco tip into the cornea. The ultrasound waves from the phaco tip emulsify the cataract so that it can be removed by suction. The surgeon first focuses on the cataract’s central nucleus, which is denser.
While the cataract is being emulsified, the machine simultaneously aspirates the cataract through a small hole in the tip of the phaco probe. The surgeon then removes the cortex of the lens, but leaves the posterior capsule, which is used to support the intraocular lens. The folded IOL is inserted by an injector. The folded IOL means that a larger incision is not required. After the IOL is inserted into the capsular bag, the viscoelastic fluid is removed. No sutures are usually required after the surgery. Some surgeons may recommend that patients wear an eye shield immediately after the surgery.
The entire procedure takes about 20 minutes. The phaco procedure itself takes only minutes. Most surgeons prefer a certain technique for the procedure, although they might vary due to the cataract’s density and size. The variations on the phaco procedure lie mostly on what part of the nucleus the surgeon focuses on first, and how the cataract is emulsified. Some surgeons prefer a continuous “chop,” while others divide the cataract into quadrants for removal. One procedure, called the “phaco flip,” involves the surgeon inverting and then rotating the lens for removal. Advances in technology also may allow for even smaller incisions, some speculate as small as 0.05 in (1.4 mm).
Diagnosis / Preparation
People might have cataracts for years before vision is impaired enough to warrant surgery. Eye doctors may first suggest eyeglasses to temporarily help improve vision. But as the lens grows cloudier, vision deteriorates.
As cataracts develop and worsen, patients may notice these common symptoms:
• gradual (and painless) onset of blurry vision
• poor central vision
• frequent changes in prescription for corrective lenses
• increased glare from lights
• near vision improvement to the point where reading glasses may no longer be needed
• poor vision in sunlight
Cataracts grow faster in younger people or diabetics, so doctors will recommend surgery more quickly in those cases. Surgery may also be recommended sooner if the patient suffers from other eye diseases such as agerelated macular degeneration and if the cataract interferes with complete eye examination.
When symptoms worsen to the point that everyday activities become problematic, surgery becomes necessary. A complete ocular exam will determine the severity of the cataract and what type of surgery the patient will receive. For some denser cataracts, the older method of extracapsular extraction is preferred.
The diagnostic exam should include measurement of visual acuity under both low and high illumination, microscopic examination of eye structures and pupil dilation, assessment of visual fields, and measurement of intraocular pressure (IOP).
If cataracts are detected in both eyes, each must be treated separately. Overall patient health must also be considered, and how it will affect the surgery’s outcome. Surgeons may recommend a complete physical examination before surgery.
Although preoperative instructions may vary, patients are usually required not to eat or drink anything after midnight the day of the surgery. Patients must disclose all medications to determine if they must be discontinued before surgery. Patients taking aspirin for blood thinning usually are asked to stop for two weeks before surgery. Blood-thinning medications may put patients at risk for intraocular bleeding or hemorrhage.
Coumadin, the prescription medicine for blood thinning, might still be taken if the risk for stroke is high. People should consult with their eye doctor and internist to decide the best course of action.
An A-scan measurement, which determines the length of the eyeball, will be performed. This helps determine the refractive power of the IOL. Other pre-surgical testing such as a chest x ray, blood work, or urinalysis may be requested if other medical problems are an issue. The surgeon may also request patients begin using antibiotic drops before the surgery to limit the chance of infection.
Cataract surgery is done on an outpatient basis, so patients must arrange for someone to take them home after surgery. On the day of the surgery, doctors will review the pre-surgical tests and insert dilating eye drops, antibiotic drops, and a corticosteriod or nonsteroidal anti-inflammatory drop. Anesthetic eye drops will be given in both eyes to keep both eyes comfortable during surgery. A local anesthetic will be administered. Patients are awake for the surgery, but are kept in a relaxed state.
The patient’s eye is scrubbed prior to surgery and sterile drapes are placed over the shoulders and head. The patient is required to lie still and focus on the light of the operating microscope. A speculum is inserted to keep the eyelids open.
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