Early in its development, phacoemulsification was performed entirely through a single incision. This single-incision/single-instrument phacoemulsification technique has previously been called a “one-handed” phaco technique. The name is a misnomer however, as two hands are required to successfully perform phaco. Rotating the lens and removing the cataract in segments can be accomplished with a single hand on the instrument, thus freeing the nondominant hand for manipulating the eye, stabilizing the globe, retrieving instruments, or stabilizing the phacoemulsification handle and tubing.
It is important that the surgeon adopt an efficient method of phacoemulsification through today's small corneal microincisions prior to adopting a single-incision technique. The single-instrument phaco technique is elegant, more efficient, easier to learn, and less traumatic to the eye, but it does require a strategy and a masterful technique. Single-incision/single-instrument phacoemulsification is a method that I call the “keyhole technique.”
INCISION CONSTRUCTION
The clear corneal microincision has placed new demands on the surgeon for evacuating the cataract through a single incision. These incisions can be very unforgiving—any distortion, tearing, or heating during the procedure may cause profound unwanted refractive effects for the eye.
Incision construction is critical to a successful phacoemulsification procedure. The incision needs to be accurately sized for the size of the phacoemulsification tip to be used. Today's cataract procedures utilize a clear corneal incision of 2.5 mm or smaller that must accommodate a microphaco tip. The clear corneal incision must be made with a blade specifically designed for the incision, such as a diamond keratome or the new disposable clear corneal incision system (Becton Dickinson Ophthalmic Surgical, Waltham, MA). I then enter the anterior chamber, and apply a viscoelastic to deepen it.
With early phacoemulsification methods, it was important to maintain the position of the cataractous lens within the capsular bag to stabilize it. After the capsulorhexis technique was introduced, surgeons found that the limited access into the capsular bag made it difficult to rotate the lens for emulsification and removal. To facilitate these maneuvers, surgeons adopted hydrodissection to cleave the strong cortical attachments between the lens capsule and the cortex of the cataract. Slipping a curved 27-gauge cannula through the incision and positioning it beneath the subincisional anterior lens capsule creates a fluid wave across the posterior lens. This maneuver prematurely loosens the cortex beneath the incision, making it easier to remove with irrigation and aspiration later in the procedure.
PHACOEMULSIFICATION PARAMETERS
I advise using a phacoemulsification machine that has individual parameters controlled by the surgeon. Phacoemulsification power should be set to a reasonable level that allows adequate control with the phaco pedal. I rarely use phaco powers above 20% to 30%. Single-incision phacoemulsification requires a higher head of infusion pressure to maintain the chamber, which allows the surgeon to delicately maneuver the phaco tip without danger of collapsing the capsular bag or injuring the corneal endothelium. I keep the irrigation bottle at a height of 115 cm.
CENTRAL SCULPTING
When performing central sculpting through a clear corneal microincision, occlusion of the phacoemulsification tip rarely occurs. The goal of this step is to remove the densest, hardest part of the nucleus at the beginning of the procedure, when it is easiest to do so. I keep the lens entirely within the capsular bag while I use the phacoemulsification tip to gently sculpt the central nucleus. If the lens nucleus is dense, I sculpt deep and wide. If the lens is soft, I sculpt narrow and shallow.
SEGMENTAL REMOVAL OF THE CORTICAL RIM—THE KEYHOLE METHOD
Once I finish central sculpting, a cortical bowl is left. To remove it, I aspirate a notch to release the tension on the cortical ring of the cataract in the peripheral cortex. Using the phacoemulsification tip as a fulcrum, I gently rotate the remaining cortical rim clockwise. I then gently aspirate two clock hours of cortical rim into the central triangle of safety, and remove them with minimal phacoemulsification. I perform an in-the-bag, three-step phacoemulsification technique with a 30&Mac251; tip. I maintain phaco power at 20%, maximum vacuum at 500 mm Hg, and an aspiration rate of 25 cm.3
REMOVING THE NUCLEAR PLATE
Once the cortical rim is completely removed, a small flat section of posterior nucleus remains. To remove this without injuring the posterior capsule, I use a mini-phaco flip technique. Using the phacoemulsification tip, I push the tip of the nuclear plate against the equator of the capsule and flip it over. I allow the piece to come to the tip rather than chase it around the posterior chamber. Using short bursts of phaco power, I can safely elevate the final piece off the posterior capsule and remove it. Next, I introduce the clear corneal irrigation-aspiration tip to remove residual cortex and irrigate the capsular bag.
INSERTING THE IOL
I fill the capsular bag with just enough viscoelastic to open the capsulorhexis. If I use a toric IOL, I align it with the steep meridian by placing the anterior lens marks at the proper location. I then carefully load the single-piece injectable lens into the injector and insert it into the capsular bag at the proper meridian in one maneuver. There, it can position itself without additional manipulation. I irrigate and aspirate to remove residual viscoelastic, and I check the lens position for proper centration. The result is a carefully controlled procedure that reshapes the cornea into a spherical, optically sound structure (kerato-), with the proper IOL fully correcting the spherical error (-lenticuloplasty).
The patient uses artificial tears as needed, and I do not provide a bandage contact lens. I give the patient a pair of sunglasses to use when outside, and he or she is seen postoperatively on the first day, at 2 weeks, 3 months, 6 months, and 1-year intervals. If a YAG laser capsulotomy is required, it is not performed until after the 3-month postoperative visit. Outcomes
The single-incision/single-instrument phacoemulsification procedure is quick, and is less traumatic to the eye. Other benefits are that it maintains the microincision, it induces less unwanted astigmatism, and it gives the surgeon better control over correcting any pre-existing refractive error with a more predictable refractive outcome. The efficiency of this technique, as well as the faster recovery for the patient, outweigh any difficulties surgeons may encounter when using a single-instrument technique.
CONCLUSION
Modern microincisional cataract surgery techniques have enabled surgeons to fully correct refractive error with cataract removal and IOL implantation. Smaller, more flexible injectable IOLs, combined with more efficient methods of phacoemulsification, have made it possible to maintain incision sizes smaller than 2.5 mm, and even as small as 1 mm. By judiciously selecting the IOL and paying careful attention to astigmatic correction, surgeons can use incision construction and toric IOLs to maximize the full refractive correction for the cataract patient. However, in order to maintain corneal sphericity, eliminate the risk of corneal burns, ensure self-sealing, unenlarged incisions, avoid capsular tears, and assure proper in-the-bag placement of the IOL, surgeons have to be diligent in their techniques. Following a time-proven plan for microincisional surgery can ensure that every surgeon delivers the best results for their patients every time.
