Phacoemulsification
Phacoemulsification (Cataracts Surgery & Lens Implantation)
Procedure for removal of the crystalline lens in cataract surgery, which consists of emulsifying and aspirating the contents of the lens with the use of a low-frequency ultrasonic needle inserted into the eye near the limbus. This technique usually produces more rapid wound healing and early stabilization of refractive error with less astigmatism, due to the small incision. However, this technique may damage the corneal endothelium if excessive ultrasound isused.
Following removal of the lens cortex and nucleus, an intraocular lens is used and can be implanted within the remaining lens capsule. The lens is folded and inserted through a small incision (e.g. 3.2 mm) using a special injector. This procedure is preferred over other cataract extraction techniques due to both the rapid wound healing and the lower incidence of potentially vision threatening side effects (e.g. retinal detachment). See after-cataract; biometry of the eye; cataract extraction; intraocular lens; iridectomy.
In cataract surgery, the lens inside your eye that has become cloudy is removed and replaced with an artificial lens (called an intraocular lens, or IOL) to restore clear vision. The procedure typically is performed on an outpatient basis and does not require an overnight stay in a hospital or other care facility.
A cataract is a clouding of the normally clear, transparent lens of the eye. A cataract is not a tumor or growth of new tissue over or in the eye. Rather it is a fogging and loss of clarity of the lens itself. The lens is located in the eye just behind the iris and the pupil. Light entering the eye is focused by the lens onto the retina. When a cataract forms, the lens is no longer able to focus the light clearly. Therefore, your vision becomes cloudy. An early cataract may cause few problems with vision. If the cataract gets worse, sight may be partially or completely lost until the cataract is removed.
Although cataracts result from many conditions, the most frequent cause is the natural ageing process. Other causes may include eye trauma, chronic eye disease and other medical conditions, such as diabetes.
Cataracts can take from a few months to several years to develop. Certain medications can accelerate the development of cataracts. Sometimes, the cataract stops developing in its early stages and vision is only slightly decreased. But if it continues to develop, vision is impaired and surgical treatment is required.
Most modern cataract procedures involve the use of a high-frequency ultrasound device that breaks up the cloudy lens into small pieces, which are then gently removed from the eye with suction.
Preparation and Precautions
Proper anesthesia is essential for ocular surgery. Topical anesthesia is most commonly employed, typically by the instillation of a local anesthetic such as tetracaine or lidocaine. Alternatively, lidocaine and/or longer-acting bupivacaine anesthestic may be injected into the area surrounding (peribulbar block) or behind (retrobulbar block) the eye muscle cone to more fully immobilize the extraocular muscles and minimize pain sensation. A facial nerve block using lidocaine and bupivacaine may occasionally be performed to reduce lid squeezing. General anesthesia is recommended for children, traumatic eye injuries with cataract, for very apprehensive or uncooperative patients and animals. Cardiovascular monitoring is preferable in local anesthesia and is mandatory in the setting of general anesthesia. Proper sterile precautions are taken to prepare the area for surgery, including use of antiseptics like povidone-iodine. Sterile drapes, gowns and gloves are employed. A plastic sheet with a receptacle helps collect the fluids during phacoemulsification. An eye speculum is inserted to keep the eyelids open.
Surgical Technique
Before the phacoemulsification can be performed, one or more incisions are made in the eye to allow the introduction of surgical instruments. The surgeon then removes the anterior face of the capsule that contains the lens inside the eye. Phacoemulsification surgery involves the use of a machine with microprocessor-controlled fluid dynamics. These can be based on peristaltic or a venturi type of pump. The phaco probe is an ultrasonic handpiece with a titanium or steel needle. The tip of the needle vibrates at ultrasonic frequency to sculpt and emulsify the cataract while the pump aspirates particles through the tip. In some techniques, a second fine steel instrument called a “chopper” is used from a side port to help with chopping the nucleus into smaller pieces. The cataract is usually broken into two or four pieces and each piece is emulsified and aspirated out with suction. The nucleus emulsification makes it easier to aspirate the particles. After removing all hard central lens nucleus with phacoemulsification, the softer outer lens cortex is removed with suction only. An irrigation-aspiration probe or a bimanual system is used to aspirate out the remaining peripheral cortical matter, while leaving the posterior capsule intact. As with other cataract extraction procedures, an intraocular lens implant (IOL), is placed into the remaining lens capsule. For implanting a poly (methyl methacrylate) (PMMA) IOL, the incision has to be enlarged. For implanting a foldable IOL, the incision does not have to be enlarged. The foldable IOL, made of silicone or acrylic of appropriate power is folded either using a holder/folder, or a proprietary insertion device provided along with the IOL. It is then inserted and placed in the posterior chamber in the capsular bag (in-the-bag implantation). Sometimes, a ciliary sulcus implantation may be required because of posterior capsular tears or because of zonular dialysis.[2] Because a smaller incision is required, few or no stitches are needed and the patient’s recovery time is usually shorter when using a foldable IOL.
