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白內障囊內摘出術(Intracapsular cataract extraction, ICCE)：大切口切開角鞏膜緣，進入後用冷凍頭凍住晶體，向外牽拉造成懸韌帶的斷裂，娩出晶體。
白內障囊外摘除術(Extracapsular cataract extraction, ECCE)：開關式截囊，娩出晶體核，同步灌注抽吸清除殘餘晶狀體皮質。
A cataract is a clouding of the lens inside the eye which leads to a decrease in vision. It is the most common cause of blindness and is conventionally treated with surgery. Visual loss occurs because opacification of the lens obstructs light from passing and being focused on to the retina at the back of the eye.
It is most commonly due to biological aging but there are a wide variety of other causes. Over time, yellow-brown pigment is deposited within the lens and this, together with disruption of the normal architecture of the lens fibers, leads to reduced transmission of light, which in turn leads to visual problems.
Those with cataracts commonly experience difficulty in appreciating colors and changes in contrast, driving, reading, recognizing faces, and coping with glare from bright lights.
Signs and Symptoms
Bilateral cataracts in an infant due to congenital rubella syndrome
Signs and symptoms vary depending on the type of cataract, though there is considerable overlap. People with nuclear sclerotic or brunescent cataracts often notice a reduction of vision. Those with posterior supcapsular cataracts usually complain of glare as their major symptom.
The severity of cataract formation, assuming that no other eye disease is present, is judged primarily by visual acuity test. The appropriateness of surgery depends on a patient's particular functional and visual needs and other risk factors, all of which may vary widely.
Age is the most common cause. Lens proteins denature and degrade over time and this process is accelerated by diseases such as diabetes and hypertension. With the passage of time, environmental factors including toxins, radiation and UV light have an accumulative effect. These effects are worsened by the loss of protective and restorative mechanisms due to alterations in gene expression and chemical processes within the eye.
Slit lamp photo of posterior capsular opacification visible a few months after implantation of intraocular lens in eye, seen on retroillumination
Cataract removal can be performed at any stage and no longer requires ripening of the lens. Surgery is usually 'outpatient' and performed using local anesthesia. Approximately 90% of patients can achieve a corrected vision of 20/40 or better after surgery.
Several recent evaluations found that surgery can only meet expectations when there is significant functional impairment from poor vision prior to surgery. Visual function estimates such as VF-14 have been found to give more realistic estimates than visual acuity testing alone. In some developed countries a trend to overuse cataract surgery has been noted which may lead to disappointing results.
Extracapsular cataract extraction (ECCE), consists of removing the lens manually, but leaving the majority of the capsule intact. The lens is expressed through a 10–12 mm incision which is closed with sutures at the end of surgery. Extracapsular extraction is less frequently performed than phacoemulsification but can be useful when dealing with very hard cataracts or other situations where emulsification is problematic. Manual small incision cataract surgery (MSICS) has evolved from extracapsular cataract extraction. In MSICS, the lens is removed through a self-sealing scleral tunnel wound in the sclera which, ideally, is watertight and does not require suturing. Although "small", the incision is still markedly larger than the portal in phacoemulsion. This surgery is increasingly popular in the developing world where access to phacoemulsification is still limited.
Intracapsular cataract extraction (ICCE) is rarely performed. The lens and surrounding capsule are removed in one piece through a large incision while pressure is applied to the vitreous membrane. The surgery has a high rate of complications.
Phacoemulsification is one of the most widely used cataract surgery nowadays. This procedure is using ultrasonic energy (U/S) to emulsifying the cataract lens. One technique in phacoemulsification is Micro Incision cataract Surgery (MICS) that is performed by a less than 2 mm (sub 2) micro incision and followed by wound assisted insertion of MICS intraocular lens (IOL). The newest procedure in cataract surgery is called Femtosecond Laser Cataract Surgery (FLCS) that is using femtosecond laser to perform capsulorhexxis, lens softening, clear corneal incision and limbal relaxing incision. This procedure still uses phaco machine to perform aspiration of lens material and perform the maneuver of irrigation-aspiration.
Phacoemulsification, typically comprises five steps, not including the anaesthetic.
Anaesthetic - The eye is numbed with either a subtenon injection around the eye or using simple eye drops.
Corneal Incision - Two cuts are made through the clear cornea to allow insertion of instruments into the eye.
Capsulorhexis - A needle or small pair of forceps is used to create a circular hole in the capsule (or bag) in which the lens sits.
Phacoemulsification - A handheld probe is used to break up and emulsify the lens into liquid using the energy of ultrasound waves. The resulting 'emulsion' is sucked away.
Irrigation and Aspiration - The cortex which is the soft outer layer of the cataract is aspirated or sucked away. Fluid removed is continually replaced with a salt solution to prevent collapse of the structure of the anterior chamber (the front part of the eye).
Lens insertion - A plastic foldable lens is inserted to the capsular bag that is used to contain the natural lens. Some surgeons will also inject an antibiotic in to the eye to reduce the risk of infection. The final step is to inject salt water in to the corneal wounds to cause the area to swell and seal the incision.
The post-operative recovery period (the period after cataract extraction is done) is usually short. The patient is usually ambulatory on the day of surgery but is advised to move cautiously and avoid straining or heavy lifting for about a month. The eye is usually patched on the day of surgery and at night using an eye shield is often suggested for several days after surgery.
In all types of surgery, the cataractous lens is removed and replaced with an artificial lens, known as intraocular lens, which stays in the eye permanently. Intraocular lenses are usually monofocal, correcting for either distance or near vision, however, multifocal lenses may be implanted to improve near and distance vision simultaneously, but these lenses may increase the chance of unsatisfactory vision.
Serious complications of cataract surgery are retinal detachment and endophthalmitis. In both cases, patients will notice a sudden decrease in vision. In endophthalmitis, patients will often describe pain. Retinal detachment frequently presents with unilateral visual field defects, blurring of vision, flashes of light or floating spots.
The risk of retinal detachment was estimated as approximately 0.4% within 5.5 years, corresponding to a 2.3x risk increase compared to naturally expected incidence, older studies reporting a substantially higher risk. The incidence is increasing over time in approximately linear manner and the risk increase lasts for at least 20 years after the procedure. Particular risk factors are younger age, male sex, longer axial length and complications during surgery. In highest risk group of patients the incidence of pseudophakic retinal detachment may be as high as 20%.
The risk of endophthalmitis occurring after surgery is less than 1 in 1000.
Corneal oedema and cystoid macular oedema are less serious but more common and occur because of persistent swelling at the front of the eye in corneal oedema or back of the eye in cystoid macular oedema. They are normally the result of excessive inflammation following surgery and in both cases, patients may notice blurred, foggy vision. They normally improve with time and with application of anti-inflammatory drops. The risk of either occurring is around 1 in 100.
Posterior capsular opacification, also known as after cataract, is a condition in which months or years after successful cataract surgery, vision deteriorates or problems with glare and light scattering recur. This is usually due to thickening of the back or posterior capsule surrounding the implanted lens, so-called ' posterior lens capsule opacification'. Growth of natural lens cells remaining after the natural lens was removed may be the cause, and the younger the patient, the greater the chance of this occurring. Management involves cutting a small, circular area in the posterior capsule with targeted beams of energy from a laser, a procedure called YAG laser capsulotomy, after the type of laser used. The laser can be aimed very accurately and the small part of the capsule which is cut falls harmlessly to the bottom of the inside of the eye. This procedure leaves sufficient capsule to hold the lens in place but removes enough to allow light to pass directly through to the retina. Serious side effects are rare. Posterior capsular opacification is common and occurs following up to 1 in 4 operations but these rates are decreasing following the introduction of modern intraocular lenses together with a better understanding of the causes.
Disability-adjusted life year for cataracts per 100,000 inhabitants in 2004.
Age-related cataracts are responsible for 51% of world blindness, about 20 million people. Globally, cataracts cause moderate to severe disability in 53.8 million (2004), 52.2 million of whom are in low and middle income countries.
In many countries surgical services are inadequate, and cataracts remain the leading cause of blindness. Even where surgical services are available, low vision associated with cataracts may still be prevalent as a result of long waits for, and barriers to, surgery - such as cost, lack of information and transportation problems.
In the United States, age-related lens changes have been reported in 42% between the ages of 52 and 64, 60% between the ages 65 and 74, and 91% between the ages of 75 and 85. Cataracts affect nearly 22 million Americans age 40 and older. By age 80, more than half of all Americans have cataracts. Direct medical costs for cataract treatment are estimated at $6.8 billion annually.
In the Eastern Mediterranean Region, Cataracts are responsible for over 51% of blindness. Access to eye care in many countries on this region is limited.