Phacoémulsification

Phacoemulsification is a cataract surgery method in which the internal lens of the eye which has developed a cataract is emulsified with the tip of an ultrasonic handpiece and aspirated from the eye. Aspirated fluids are replaced with irrigation of balanced salt solution to maintain the volume of the anterior chamber during the procedure. This procedure minimises the incision size and reduces the recovery time and risk of surgery induced astigmatism. It is best suited to relatively soft cataracts, where the ultrasonic energy required is moderate, and insertion of foldable intraocular prosthetic lenses, which take advantage of the small incision possible. It is the most common procedure for cataract removal in the developed world, with an excellent prognosis in uncomplicated cases. The term originated from phaco- (Greek phako-, comb. form of phakós, lentil; see lens) + emulsification. The same general contraindications for cataract surgery apply. Specific contraindications for phacoemulsification include hard or dense cataracts where phacoemulsification is likely to cause permanent damage to the cornea. The phacoemulsification system comprises three sub-systems: Ultrasound, aspiration, and irrigation. The ultrasound component is used to break the lens down into particles small enough to be aspirated through the suction passages around the tip, which allows a very small incision for access. The incision is small enough that sutures are not needed for closure, and very little astigmatism is caused by healing of the wound in the cornea. The phacoemulsification handpiece has a tip which vibrates longitudinally at a frequency in the range of 27 to 60 kHz, with a stroke length of 60 to 150 micrometres. Power is adjustable by the operator as a percentage of full power, and indicates a variation in nominal stroke length. Actual stroke length may vary slightly depending on the density of the material it contacts, though some instruments use feedback to maintain nominal stroke by adjusting current, voltage or frequency.