As the primary aim of cataract surgery is to restore visual clarity and quality, measures to maximize the final postoperative visual outcome inevitably take center stage. Great consideration is therefore given to maximizing the accuracy of preoperative calculations, selecting the most appropriate type of IOL, and planning to minimize residual refractive error. All these issues are important; however, the manner in which the cataract itself is removed requires equal consideration.
Phacoemulsification is the preferred method for removal of the opacified lens, and nucleus division is typically achieved via chopping or sculpting. However, these methods carry specific risks of collateral damage. Chopping reduces overall phacoemulsification time, but it is difficult to master. In contrast, sculpting is easier to learn but increases phacoemulsification time and thus the risk of complications including postoperative inflammation and corneal edema.
REDUCING LENS DIVISION COMPLICATIONS
I have developed a new nucleusdivision strategy, the phacotunnel technique, that integrates the benefits of chopping and sculpting while reducing some of their most dangerous features. A video of the procedure can be viewed at eyetube.net/?v=jojee.
This technique allows the surgeon to achieve lens division without using a complex bimanual technique. The bimanual techniques often used during chopping can be difficult to master because they require the surgeon to impale the lens nucleus with his or her dominant hand and chop the lens with his or her nondominant. The phacotunnel approach eliminates the need for chopping and also permits quicker lens division with less ultrasound time than sculpting.
The phacotunnel technique is suitable only for eyes with moderate to hard cataracts (Lens Opacities Classification System grade 3 or higher), not for soft lenses. I have found that its greatest advantage, reduced tissue damage, is achieved when the phacotunnel is performed with a 1.8-mm phaco tip and sleeve using the Stellaris Vision Enhancement System (Bausch + Lomb).
The procedure begins by introducing the phaco tip in the center of the nucleus, impaling the nucleus (Figure 1) and thus creating a tunnel, using low ultrasound energy. A high vacuum setting (400 mm Hg) is required. Insertion of the phaco tip should continue until it is buried in the lens.
With the tip still buried in the tunnel, the surgeon should reduce vacuum power to 30 mm Hg while applying ultrasound and pointing the phaco tip bevel upward, toward the roof of the tunnel. This is continued until the tip breaks through to the lens surface. In doing so, the roof above the tunnel is removed (Figure 2) and a deep groove is created. Sculpting can then be used to achieve an appropriate groove depth and width (Figure 3).
The tunneling maneuver and subsequent roof removal is repeated in all quadrants of the lens (Figure 4), and phacoemulsification is then completed using a conventional divide-and-conquer technique (Figure 5). The eye must be irrigated with balanced saline solution throughout the procedure.
THE KEY TO EFFICACY
Because the phacotunnel technique uses vacuum to counteract the force of impaling the phaco tip, zonular tension is reduced compared with a standard grooving technique. The phacotunnel procedure also minimizes endothelial damage by trapping lens fragments and the ultrasound energy cone within the tunnel. Additionally, substituting vacuum for ultrasound energy ensures that less ultrasound is used.
It should be noted that thermal damage can occur with the phacotunnel method because irrigation is reduced during the impaling stage. This can be avoided by using ultrasound modulation to reduce heat at the phaco tip.
Not only does the phacotunnel technique employ a clear step-bystep method, but also the absence of a complicated bimanual technique helps to reduce trainee anxiety and learning curve complications.
It is important to note that the technique carries a risk of sudden surge that can occur if the high 400 mm Hg vacuum power used during impaling is not reduced to 30 mm Hg before breaking through the tunnel roof. Once the vacuum power is decreased, the phaco tip can safely be moved toward the lens surface to remove the roof without loss of chamber stability.
I have been using this technique since 2001 and have experienced encouraging results, with a capsular or zonular disruption rate of 1.0% and a vitreous loss rate of 0.3%.
ADVANCING PHACOEMULSIFICATION TECHNIQUES
The phacotunnel technique provides the means for surgeons to advance their surgical techniques along with the available technologies. The phacotunnel technique can be used to divide cataracts with low risk of complications and can be performed with most types of phaco machines. I believe that this technique offers a new and improved approach for safe and effective phacoemulsification.
Marcos Gomez García, MD, is Director of the Cataract Surgery Center at Hospital Malvarrosa, Valencia, Spain. Dr. Gomez states that he no financial interest in the products or companies mentioned. He may be reached at e-mail: email@example.com.