Refractive lensectomy: principles/technique will aid in assuring safe lens extraction

Issue: February 1, 2000

The technique of clear lens extraction is much like removing a very soft cataract, only more so. The soft lensectomy presents a unique set of challenges that must be clearly understood and carefully addressed in order to assure that the lens is efficiently removed without complication. Al though refractive lensectomy is still a relatively new approach as a primary refractive procedure, there are several principles that have emerged and are common to almost all surgeons that I know who are regularly performing refractive lensectomy. Lets first outline these principles and then discuss the technique in detail.

The soft lensectomy: general principles

---Continuous, well-centered CCC with a diameter greater than 5 mm and less than 6 mm.

These general principles are important guidelines for safe, efficient removal of the clear lens:

Concern for capsule over cornea. The relative concern for capsule and corneal endothelium is under constant consideration when evaluating alternative lensectomy techniques. Removal of the soft clear lens allows us to shift our emphasis toward protecting the capsule at all costs when selecting our lensectomy approach. Appropriate viscoelastic selection, combined with rapid lens evacuation, insures adequate endothelial protection for the typical refractive lensectomy candidate.

Maximize access to the lens. The soft lens is typically difficult to maneuver, since instruments tend to pass through its substance. Generally, this inherent immobility, combined with the tendency for the soft lens to remain firmly adherent to the capsular bag, are more easily managed if access to the lens is enhanced with a slightly larger diameter continuous curvilinear capsulorrhexis (CCC).

Loosen the lens. Successful removal of the clear lens depends primarily upon this step. Only after all lens-capsule attachments have been completely cleaved will the soft lens succumb to aspiration and evacuation without risk to the capsule.

Relocate the lens into the anterior chamber. It is almost universally agreed among experienced refractive lensectomy surgeons that the lens removal should take place in the anterior chamber where it can be efficiently and rapidly evacuated without endothelial or capsular damage.

The soft lensectomy: step by step

---Cortical cleaving hydrodissection to completely loosen the lens from the capsule.

Intact CCC 5 to 5.5 mm in diameter. The slightly larger intact CCC will readily accommodate the following steps. It also is recommended by David Apple and co-workers as the optimal diameter CCC to “shrink-wrap” the IOL into the capsular bag in order to reduce posterior capsule opacification (PCO).

Cortical cleaving hydrodissection. This technique, originally described by I. Howard Fine, MD, plays an important role in the soft lensectomy. By lifting the cannula after it is positioned under the anterior capsule and then steadily injecting, the hydrodissection fluid wave creates a cleavage plane between capsule and peripheral lens, thus completely separating all capsule-lens attachments. It is important not to discontinue the hydro dissection prematurely. As long as the CCC is 5 to 5.5 mm, the soft lens will sub lux anteriorly up through the CCC well before there is any risk of the fluid wave rupturing the posterior capsule.

The steps to cortical cleaving hydro dissection are as follows:

Place the cannula under the capsule. Avoid any contact between your thumb and the syringe plunger so as to avoid inadvertent hydration of the lens material.
Elevate the cannula and anterior capsule.
Steadily inject hydrodissection fluid while maintaining elevation of cannula, until the fluid wave is seen to pass completely beneath the lens … and ideally until the lens begins to tilt up through the CCC.

Lens tilt. With experience, the lens is typically tilted up into the CCC with hydrodissection. Until one develops the confidence to persist with hydrodissection, the process can be divided into two separate steps. The first hydrodissection to create a fluid wave and the second to tilt the lens.

---Allow the hydrodissection to tilt the lens up through the CCC, then rotate it into the anterior chamber for phacoaspiration.

Rotate lens into anterior chamber. Once the lens is tilted, it is usually easy to rotate it up and through the CCC. Viscoelastic can sometimes assist it keeping the lens tilted during this maneuver. Only when the lens is out of the capsule and completely into the anterior chamber, is it ready for phacoaspiration. It is best to avoid phacoaspiration while the lens is still partially within the capsular bag.

Anterior chamber phacoaspiration. A standard phaco tip with a 15° or 30° tip is typically used to aspirate the soft lens with low power, slow-pulsed phaco assistance as needed. The capsule-free soft lens is usually evacuated efficiently and rapidly. A nucleus rotator is sometimes helpful to maneuver the lens toward the phaco tip, but the higher aspiration level usually provides excellent followability on it own.

Cortex removal. Cortical cleaving hydrodissection ideally leaves little or no residual cortex as it typically is removed with the lens material during the final stages of anterior chamber phacoaspiration. When cortex remains, it must be meticulously removed as Apple and co-workers have advised us that this is another major factor contributing to PCO. The larger CCC is often a great help in this step, particularly by providing greater access to the subincisional area.

Safe and efficient soft lens removal depends primarily on complete loosening and removal of the lens from the capsular bag. A slightly larger CCC and cortical cleaving hydrodissection allow for relocation of the lens into the anterior chamber for final evacuation using phaco aspiration. In the near future, we may see new technology emerge, which may be even better suited to soft lensectomy such as laser phaco or the CataRhex (Oertli Instrumente AG, Berneck, Switzerland) technology.

Next month: Potential problems unique to hyperopic refractive lensectomy.