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Technique

Irrigating chopper and vacuum capsulorhexis

A new technique in phacoemulsification

Andrioli, Lucas L. MD*

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Journal of Cataract & Refractive Surgery: November 2004 - Volume 30 - Issue 11 - p 2262-2264
doi: 10.1016/j.jcrs.2004.02.087
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Abstract

Continuous curvilinear capsulorhexis (CCC) was described and developed independently by Gimbel and Neuhann1 in 1986. The evolution of intraocular lenses (IOLs) that enable better folding and the possibility of injecting collagen polymers or other substances into the capsular bag through minimal incisions (M. Packer, MD, et al., “Perspectives in Lens and IOL Surgery: Highlights of the 2002 ASCRS Symposium,” EyeWorld, August 2002, page 26; J.J. Bovet, MD, et al., “Phacoemulsification Through a 1.0 mm Incision and IOL Insertion Through a 1.7 mm Incision,” presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, April 2003) makes smaller incisions a major goal (M.K. Gupta, MD, “Bimanual Microphacoemulsification Using WhiteStar Technology,” and L. Izquierdo, MD, et al., “Microphaco Using the Staar Wave Sonic and NeoSoniX,” presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, April 2003).

As the search for smaller phaco incisions progresses, surgeons face challenges such as the performance of CCC through very small incisions (ie, 1.0 mm or less).2,3 Cystotomes (25-gauge or 27-gauge needle with a 90-degree curved tip) and various models and sizes of forceps are used to perform CCC. If a forceps is used, an ophthalmic viscosurgical device (OVD) is needed to maintain anterior chamber depth (ACD). This is achieved through 2.00 to 3.25 mm incisions, which make opening and closing the forceps possible. If cystotomes are used, an OVD can be instilled or an additional incision made to maintain the ACD.4

I describe a technique that allows a CCC of approximately 6.0 mm in diameter (range 5.8 to 6.2 mm) to be performed through a 1.0 mm incision using vacuum traction. The ACD is maintained with an irrigating chopper without placing an OVD.

Surgical Technique

Aspiration System

An aspiration cannula (Simcoe model) is connected to the phaco aspiration pump system, ie, the outlet system of the peristaltic pump tube, by a 1.5 mm wide and approximately 40 cm long catheter. This way, the phaco footpedal can regulate the aspiration achieved with the cannula tip. A vacuum of 250 mm Hg with a flow rate of 25 cc is established. In the irrigation system, a horizontal irrigating chopper (19-gauge, microfinger style, Rhein) is attached to a tube with a bottle of 500 cc balanced salt solution (BSS®). The bottle is positioned 45 cm above the patient's head to maintain anterior chamber (AC) stability.

A bevel-edge side-port incision, commonly made in phaco surgery for the chopping instrument, is made at approximately 3 o'clock with a diamond knife. To achieve appropriate pressure in the AC, the irrigating chopper is introduced while the bottle is raised, according to the features of the eye to be treated. Using the same knife, the second incision is made at the same site where the main phaco entry incision will be completed. A capsule tear is made through this incision with a cystotome, and a Simcoe cannula connected to the phaco aspiration device is introduced. The torn flap is grabbed by activating the phaco footpedal on aspiration, producing several successive tears (3 or 4 grabs are usually enough) until the capsulorhexis is completed (Figure 1).

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Figure 1.:
(Andrioli) Vacuum CCC with an irrigating chopper.

Patients and Methods

Vacuum CCC was performed in 30 patients from August to December 2002. The desired CCC was approximately 6.0 mm in diameter (range 5.8 to 6.2 mm). To obtain the desired diameter, the capsulorhexis was measured vertically and horizontally with a compass and the mean determined from the 2 diameters.

Exclusion criteria included glaucoma, pseudoexfoliation syndrome, the presence or history of corneal or iris disease, secondary cataract, pediatric cataract, +5.0 diopters (D) of hyperopia, and –6.0 D of myopia. To compare the values of the desired CCC and the achieved CCC, a Student t test was used with α = 0.05 along with a scatterplot diagram.

Results

The desired capsulorhexis was achieved in 19 patients. In 7 patients, the capsulorhexis diameter was smaller than the desired one, and in 2 patients, it was larger. Values below the desired capsulorhexis were never less than 4.6 mm.

In 95% of cases, the capsulorhexis was between 5.79 mm and 6.00 mm, within the range of the desired diameter. In 2 patients, a tear extended from the desired CCC. The tears were located at 12 o'clock and in both cases, the capsulorhexis was completed using an OVD and a Utrata forceps; thus, the integrity of the CCC edge was maintained. Neither zonule disruption by traction nor vitreous loss was observed in any case. In the 30 cases, the mean achieved CCC was 5.807 mm ± 0.569 (SD). The differences between the desired CCC and the achieved CCC were not statistically significant (P = .73).

Discussion

Brierley5 first described vacuum capsulorhexis in 1995. He used an aspiration device consisting of a syringe attached to a catheter; the catheter was connected to a handpiece, which connected to an aspiration cannula for the procedure. The left hand was used to aspirate or inject fluid with the syringe, and the right hand was used to operate the handpiece and the aspiration cannula to capture the capsule. The cannula was inserted through an incision at 10 o'clock. To maintain AC stability, Brierley used an anterior chamber maintainer (ACM) through an additional incision. Thus, phacoemulsification required 4 incisions: for the ACM, the aspiration cannula, the second instrument (chopper), and the main entry site.

Three modifications are proposed in my technique: (1) maintaining stable pressure in the AC using an irrigating chopper, (2) connecting the cannula–handpiece–catheter system to the aspiration pump of the phaco machine, and (3) performing the procedure through 2 incisions. Stability of the AC was achieved while the CCC was made, the vacuum was accurately controlled for successive tears, and the number of necessary incisions was reduced to 2.

The greatest difficulty in the first cases occurred when the torn flap was grabbed by vacuum, since the flap could sometimes get loose or tear. A statistical test (Figure 2) showed the importance of the learning curve when performing this modified surgical procedure; the more patients in whom CCC was performed, the closer the results to the desired diameter.

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Figure 2.:
(Andrioli) Scatterplot showing the desired and achieved vacuum CCC.

Irrigating choppers have significantly increased the safety and efficiency of bimanual surgery. Superb fluidics are critical to maintain a stable AC environment while the vacuum is used. With the previously mentioned parameters (position of the bottle, flow rate, aspiration, and cannula used), it became clear to me that the 19-gauge (1.05 mm) irrigating chopper is a better size since, in some cases, the amount of flow into the eye with a 20-gauge (0.9 mm) irrigating chopper was insufficient to maintain AC stability.

Although the data are based on 30 cases, I have used the irrigating chopper and vacuum capsulorhexis technique in all my phacoemulsification surgeries and in more than 300 cases. Complications were observed in fewer than 1% of cases.

This modified vacuum capsulorhexis procedure has advantages over the vacuum capsulorhexis previously described: The CCC is made through a 1.0 mm incision; only 2 incisions are made, 1 for the chopper and the other for the aspiration cannula; the main incision is used for the capsulorhexis; the 2 incisions are used for the remaining phacoemulsification steps—the aspiration cannula incision is used to introduce the phaco tip, with a sleeve or with the forthcoming “sleeveless phaco,” and the chopper incision for the 2-handed phacoemulsification; the results can be replicated; the learning curve is short, as the capsular grasp achieved with the aspiration system is similar to that performed with the forceps; and although diluted OVD can be used, it is possible to perform the procedure without it.

There are studies that describe the use of the irrigating chopper. However, the capsulorhexis is performed under OVD. Because of current advances and refinement in performing the procedure, CCC is a challenge during cataract extraction surgery. I believe this technique can contribute to the search for smaller incisions in phacoemulsification.

References

1. Gimbel HV, Neuhann T. Development, advantages, and methods of the continuous circular capsulorhexis technique. J Cataract Refract Surg 1990; 16:31-37
2. Blumenthal M, Ashkenazi I, Assia E, Cahane M. Small-incision manual extracapsular cataract extraction using selective hydrodissection. Ophthalmic Surg 1992; 23:699-701
3. Navon SE Adamis AP. Safety during the transition to phacoemulsification: a survey. Int Ophthalmol Clin 1994; 34(3):51-65
4. Lewicky AO, Lopez OI, Petkus RW, Stillerman ML. The Chamber Maintainer System (CMS). Ophthalmic Surg 1982; 13:921-927
5. Brierley L. Vacuum capsulorhexis. J Cataract Refract Surg 1995; 21:13-15
© 2004 by Lippincott Williams & Wilkins, Inc.