When starting to perform cataract surgery, most surgeons first learn the divide-and-conquer technique. This technique is especially useful in medium-hard cataracts. In these cases, the density of the lens allows two clean trenches to be sculpted in a cross pattern, and the edges of the trenches provide sufficient resistance to allow the phaco tip and the tip of the second instrument to separate the lens into quadrants.
In harder nuclei, a chopping technique may be more advantageous, as a relatively large amount of phaco energy would be required to create the trenches for the classic divide-and-conquer technique. Additionally, the smaller lens fragments that are created with the chopping technique can be emulsified more efficiently.
With soft lenses, however, the consistency of the lens matter may be too soft to create trenches for the divide-and-conquer technique. Further, the lens may not crack easily, as its soft material provides insufficient resistance to the phaco tip and the second instrument when one attempts to separate the parts. This results in slicing through the lens instead of cracking it, even when the two instruments are held parallel to each other to increase the area over which pressure is applied.
Soft lenses are especially common in patients who develop cataracts at a young age. Common examples are posterior subcapsular cataracts (which may be secondary to systemic or topical use of steroids) and cataracts secondary to uveitis, trauma, or vitrectomy.
SURGICAL APPROACH
For the surgical management of these cases, I prefer to use a prolapse-and-flip technique. In a soft lens, the central nucleus is often a bit harder than the periphery and may require some phaco power to emulsify. If the small central nucleus is separated from the remaining soft lens, as little energy as possible will be needed. Hydrodissection is performed as usual after the anterior capsulorrhexis has been created. With hydrodissection, it is imperative to see a posterior wave of injected balanced saline solution, indicating that the adhesions between the cortex and the posterior capsule have been broken.
Then, to break the connections between the cortex and anterior lens capsule, an anterior wave must be created circumferentially around the lens. The tip of the cannula can be used to gently press down and centripetally on the lens at two or three locations around the lens. This will move the fluid that was trapped behind the lens from hydrodissection forward, thereby breaking the anterior corticocapsular adhesions.
When the anterior wave has passed around the entire lens, the lens will be able to rotate freely within the bag. Then the central nucleus must be lifted out of the bag. To achieve this, the tip of the cannula is placed deep into the nucleus of the lens. Balanced saline solution is then injected (Figure 1A) until the central nucleus is lifted into the anterior chamber (Figure 1B). Sometimes, several attempts may be needed to lift the harder central nucleus out of the bag.
Once the central part of the lens is out, it can be easily emulsified with the phaco tip (Figure 1C). The remaining epinucleus is soft and can be aspirated with phacoaspiration; this requires little or no phaco power. To lift the epinucleus out of the bag, the opening of the phaco tip is best placed against the epinucleus. This will ensure that when one pushes the footpedal into position 2, one has immediate occlusion of the tip and the epinucleus can be pulled out of the bag. For this reason, it may be easier to have the opening of the tip turned downward instead of having the bevel pointing upward; it may be more difficult to achieve occlusion with the bevel pointed upward as the tip may not be fully covered by lens material.
Depending on preference, the surgeon can then keep the tip with its bevel positioned downward (bevel down) or rotate the tip with its opening back up (bevel up). To get the epinucleus out of the bag, it may be advantageous to flip the epinucleus (Figure 1D). It is helpful that the central part of the nucleus has been removed so that the remaining epinucleus can be folded onto itself. Then the epinucleus can be grasped at the 6-o’clock position and a second instrument used to push the epinucleus toward the 6-o’clock position. This will facilitate lifting the epinucleus out of the bag.
If the epinucleus is difficult to grasp, and flipping the epinucleus is unsuccessful, a bolus of ophthalmic viscosurgical device (OVD) can be injected behind the epinucleus so that it will prolapse into the anterior chamber. For this purpose, it does not matter whether a cohesive or a dispersive OVD is used, as its only task is to lift the epinucleus into the anterior chamber and away from the posterior capsule. Once the epinucleus is within the anterior chamber, the OVD is easy to aspirate.
CONCLUSION
The classic divide-and-conquer technique is useful in many circumstances. In a soft lens, however, a phacoaspiration technique, such as the prolapse-and-flip technique described above, may be more efficient.
Nic J. Reus, MD, PhD, is an ophthalmologist in the Department of Ophthalmology, Amphia Hospital, Breda, the Netherlands. Dr. Reus states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +31 76 595 1077; e-mail: nreus@amphia.nl.
