Cortical Cleaving Hydrodissection

Introduction

Hydrodissection of the nucleus in cataract surgery has traditionally been perceived as the injection of fluid into the cortical layer of the lens under the lens capsule to separate the lens nucleus from the cortex and capsule.¹ With increased use of continuous curvilinear capsulorrhexis^2-3 and phacoemulsification in cataract surgery, hydrodissection became an important step to mobilize the nucleus within the capsule for disassembly and removal.^4-7 Following nucleus removal, cortical cleanup was a separate step, using irrigation and aspiration (I&A) handpieces.

Fine has previously described cortical cleaving hydrodissection,⁸ which is a hydrodissection technique designed to cleave the cortex from the lens capsule and, thus, leave the cortex attached to the epinucleus. Cortical cleaving hydrodissection usually eliminates the need for cortical cleanup as a separate step in cataract surgery by phacoemulsification, thereby eliminating the risk of capsular rupture during cortical cleanup.

Technique

A small capsulorrhexis size of 5 mm to 5.5 mm optimizes cortical cleaving hydrodissection. The large anterior capsular flap makes this type of hydrodissection easier to perform. The anterior capsular flap is elevated away from the cortical material with a 26-gauge blunt cannula (e.g., Katena Instrument No. K7-5150) prior to hydrodissection. The cannula maintains the anterior capsule in a tented-up position at the injection site near the lens equator. Irrigation before elevation of the anterior capsule should be avoided because it will result in transmission of a fluid wave circumferentially within the cortical layer, hydrating the cortex and creating a path of least resistance that will disallow later cortical cleaving hydrodissection. Once the cannula is properly placed and the anterior capsule is elevated, gentle, continuous irrigation results in a fluid wave that passes circumferentially in the zone just under the capsule, cleaving the cortex from the posterior capsule in most locations. When the fluid wave has passed around the posterior aspect of the lens, the entire lens bulges forward because the fluid is trapped by the firm equatorial cortical-capsular connections. The procedure creates, in effect, a temporary intraoperative version of capsular block syndrome as seen by enlargement of the diameter of the capsulorrhexis. At this point, if fluid injection is continued, a portion of the lens prolapses through the capsulorrhexis. However, if prior to prolapse the capsule is decompressed by depressing the central portion of the lens with the side of the cannula in a way that forces fluid to come around the lens equator from behind, the cortical-capsular connections in the capsular fornix and under the anterior capsular flap are cleaved. The cleavage of cortex from the capsule equatorially and anteriorly allows fluid to exit from the capsular bag via the capsulorrhexis, which constricts to its original size, and mobilizes the lens in such a way that it can spin freely within the capsular bag. Repeating the hydrodissection and capsular decompression starting in the opposite distal quadrant may be helpful. Adequate hydrodissection at this point can be demonstrated by the ease with which the nuclear-cortical complex can be rotated by the cannula.

Completion of the Procedure

After evacuation of all endonuclear material, the epinuclear rim is trimmed in each of the quadrants also mobilizing cortex in the following way. As each quadrant of the epinuclear rim is rotated to the distal position in the capsule and trimmed, the cortex in the adjacent capsular fornix flows over the floor of the epinucleus and into the phaco tip. Then the floor is pushed back to keep the bag on stretch until three of the four quadrants of the epinuclear rim and forniceal cortex have been evacuated. It is important not to allow the epinucleus to flip too early, thus avoiding a large amount of residual cortex remaining after evacuation of the epinucleus.

The epinuclear rim of the fourth quadrant is then used as a handle to flip the epinucleus. As the remaining portion of the epinuclear floor and rim is evacuated from the eye, 70% of the time, the entire cortex is evacuated with it.⁹ Downsized phaco tips with their increased resistance to flow are less capable of mobilizing the cortex because of the decreased minisurge accompanying the clearance of the tip when going from foot position 2 to foot position 3 in trimming of the epinucleus.

After the intraocular lens is inserted, strands and any residual viscoelastic material are removed using the I&A tip, leaving a clean capsular bag.

If cortex is remaining following removal of all the nucleus and epinucleus, three options can be employed. The first option is that the phacoemulsification handpiece can be left high in the anterior chamber while the second handpiece strokes the cortex-filled capsular fornices. Frequently, this results in the cortical shell floating up as a single piece and exiting through the phacoemulsification tip (in foot position 2), because cortical cleaving hydrodissection has cleaved most of the cortical capsular adhesions.

Alternatively, if one wishes to complete cortical cleanup with the I&A handpiece before lens implantation, the residual cortex can almost always be mobilized as a separate and discrete shell (reminiscent of the epinucleus) and removed without ever turning the aspiration port down to face the posterior capsule.

The third option involves viscodissecting the residual cortex by injecting the viscoelastic through the posterior cortex onto the posterior capsule. We prefer a dispersive viscoelastic such as Viscoat (chondroitin sulfate-hyaluronate, Alcon). The viscoelastic material spreads horizontally, elevating the posterior cortex and draping it over the anterior capsular flap. At the same time, the peripheral cortex is forced into the capsular fornix. The posterior capsule is then deepened with a cohesive viscoelastic such as Provisc (1% sodium hyaluronate, Alcon), and the intraocular lens (IOL) is implanted through the capsulorrhexis, leaving the anterior extension of the residual cortex anterior to the IOL.

Removal of residual viscoelastic material accompanies mobilization and aspiration of residual cortex anterior to the IOL, which protects the posterior capsule, leaving a clean capsular bag.

Conclusion

In summary, the lens can be divided into an epinuclear zone with most of the cortex attached and a more compact central nuclear mass. The central portion of the cataract can be removed by any endolenticular technique, after which the protective epinucleus is removed with all or most of the cortex attached. In most cases, I&A of the cortex as a separate step is not required, thereby eliminating that portion of the surgical procedure and its attendant risk of capsular disruption. Residual cortical cleanup may be accomplished in the presence of a posterior chamber IOL, which protects the posterior capsule by holding it remote from the aspiration port.

References

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Gimbel HV, Heuhann T. Development, advantages, and methods of the continuous circular capsulorrhexis technique. J Cataract Refract Surg. 1990;16:31-37.

Davison JA. Bimodal capsular bag phacoemulsification: A serial cutting and suction ultrasonic nuclear dissection technique. J Cataract Refract Surg. 1989;15:272-282.

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Gimbel HV. Divide and conquer nucleofractis phacoemulsification: Development and variations. J Cataract Refract Surg. 1991;17:281-291.

Fine IH. The chip and flip phacoemulsification technique. J Cataract Refract Surg. 1991;17:366-371.

Fine IH. Cortical cleaving hydrodissection. J Cataract Refract Surg. 1992;18(5):508-512.

Fine IH. The choo-choo chop and flip phacoemulsification technique. Operative Techniques in Cataract and Refractive Surgery. 1998;1(2):61-65.