way to consistently remove viscoelastics.16,17 Recently Tetz and Holzer18 have demonstrated the twocompartment technique to be equally effective. Healon5 is best removed using one of these two techniques. The settings (Table 24–4) cause sufficient turbulence to achieve easy fracturing of the Healon5 matrix. The aspiration flow rate is set at 28 to 30+ cc/min. The vacuum is set at 350 to 500 mm Hg. The bottle height is set at 70 to 90 cm above the patient’s eye. A 0.3-mm I&A tip aspiration port size is used. In the rock ’n’ roll technique the I&A tip is placed on the surface of the IOL and the foot pedal is fully depressed. The I&A tip is now rolled back and forth across the surface of the IOL. This allows irrigation fluid to crack the matrix of the Healon5, allowing aspiration of the pieces. Simultaneously, slight posterior pressure from the I&A tip on the surface of the lens, alternately tilting the IOL about 45 degrees to the left and right, mobilizes the mass of viscoelastic

TABLE 24–4 “ROCK ‘N’ ROLL” REMOVAL

TECHNIQUE FOR HEALON5*

Vacuum 350 to 500 mm Hg Flow rate 25 to 35 mL/min Bottle height 70 to 90 cm

Irrigation and aspiration (I&A) tip port size 0.3

*An effective technique to remove Healon5 must create sufficient turbulence to make Healon5 fracture into pieces.

posterior to the IOL as it is gently rocked from side to side. The I&A tip is not placed behind the IOL. The IOL remains as a barrier between the I&A tip and posterior capsule, thus protecting the posterior capsule from contact with the aspiration port while the vacuum level is set so high. The turbulence created by aggressive irrigation fractures the Healon5, and high vacuum settings are used to aspirate the very viscous Healon5. This part of the procedure is rapid, often lasting less than 40 seconds with Healon5. However, the end point is complete removal of the viscoelastic regardless of the time elapsed. In the two-compartment technique, the IOL is placed into the capsular bag and not centered. The I&A tip is then placed behind the IOL into the capsular bag, and I&A is commenced with similar settings to the rock ’n’ roll technique above. Once the capsular bag is evacuated, the I&A is placed in front of the IOL and is used to center the IOL, and the remainder of the OVD is aspirated. The two-compartment technique is slightly quicker than the rock ’n’ roll technique but involves placing the I&A between the IOL and the posterior capsule, and so slightly increases the risk of snagging the posterior capsule.

CONCLUSION

During the past few years, two viscoelastic strategies have emerged as superior methods for dealing with complications in cataract surgery. These are the soft

shell technique and Healon5. Both methodologies employ the principle of the use of viscoelastics to achieve spatial partitioning of the surgical field into

(1) a viscoelastic protected zone and (2) a surgical fluid flow zone. Additionally, OVDs are superb at creating and maintaining space and equalizing pressure. To deal effectively with the varied uses of viscoelastics in complicated surgery, the surgeon must understand certain basic principles. Viscoelastics can be used as a powerful tool to improve surgical outcomes in complicated cases.

ACKNOWLEDGMENTS

The video of the soft shell technique won first place in the category of surgical techniques at the ASCRS Alcon Film Festival, Seattle, June 1996. A second video, dealing with the use of the soft shell technique for complications, won the runner-up award in the category of surgical techniques at the ASCRS Alcon Film Festival, Boston, May 1998. (These two videos and a video of Healon5 and viscoadaptivity, shown at the ASCRS film festival, Seattle, April 1999, are available from Alcon and Pharmacia, respectively.)

REFERENCES

1.Arshinoff S. New terminology: ophthalmic viscosurgical devices [guest editorial]. J Cataract Refract Surg 2000;26:627–628.

2.Arshinoff SA. The physical properties of ophthalmic viscoelastics in cataract surgery. Ophthalmic Pract 1991;9:1–7.

3.Arshinoff SA. Dispersive and cohesive viscoelastic materials in phacoemulsification. Ophthalmic Pract 1995;13:98–104.

4.Arshinoff SA. Dispersive and cohesive viscoelastic materials in phacoemulsification: revisited 1998. Ophthalmic Pract 1998;16:24–32.

5.Caporossi A, Baiocchi S, Sforzi C, Frezzotti R. Healon GV vs. Healon in demanding cataract surgery. J Cataract Refract Surg 1995;21:10–13.

6.Lehmann R, Brint S, Stewart R, et al. Clinical comparison of Provisc and Healon in cataract surgery. J Cataract Refract Surg 1995;21:543–547.

7.Arshinoff SA, Hofmann I. Prospective, randomized trial of Microvisc and Healon in routine phacoemulsification. J Cataract Refract Surg 1997;23:761–765.

8.Arshinoff SA, Hofmann I. A prospective, randomized trial comparing Microvisc Plus to Healon GV in routine phacoemulsification. J Cataract Refract Surg 1998; 24:814–820.

9.Arshinoff SA. Comparative physical properties of ophthalmic viscoelastic materials. Ophthalmic Pract 1989;7:16–36.

10.Madsen K, Stenevi U, Apple D, Harfstrand A. Histochemical and receptor binding sites of hyaluronic acid and hyaluronic acid binding sites on the corneal endothelium. Ophthalmic Pract 1989;7:2–8.

11.Poyer JF, Chan KY, Arshinoff SA. A new method to measure the retention of viscoelastics on a rabbit corneal endothelial cell line after irrigation and aspiration. J Cataract Refract Surg 1998;24:84–90.

12.Assia EI, Apple DJ, Lim ES, et al. Removal of viscoelastic materials after experimental cataract surgery in vitro. J Cataract Refract Surg 1992;18:3–6.

13.Arshinoff SA, Calogero DX, Bilotta R, et al. Post operative IOP, endothelial cell counts, and pachymetry after viscoelastic use in cataract surg (in press). Presented by S. Senft at the American Society of Cataract and Refractive Surgery annual meeting, Boston, April 1998.

14.Arshinoff S. The dispersive/cohesive viscoelastic soft shell technique for compromised corneas and anterior chamber compartmentalization. American Society of Cataract and Refractive Surgery film festival, Seattle, June 1–5, 1996.

15.Arshinoff SA. Dispersive-cohesive viscoelastic soft shell technique. J Cataract Refract Surg 1999;25:167– 173.

16.Arshinoff S. Rock ’n’ roll removal of Healon GV (video). American Society of Cataract and Refractive Surgery film festival, Seattle, June 1–5, 1996.

17.Arshinoff SA. Rock ’n’ roll removal of Healon GV. In: Arshinoff SA, ed. Proceedings of the 7th Annual National Ophthalmic Speakers Program, Ottawa, Canada, June 1996. Medicopea, 1997.

18.Tetz MR, Holzer MP. Two-compartment technique to remove ophthalmic viscosurgical devices. J Cataract Refract Surg 2000;26:641–643.

Complications related to the phaco machine can generally be grouped into two categories. First, the inappropriate use of machine parameters may result in direct tissue damage through such mechanisms as chamber collapse, corneal wound burn, iris incarceration, and capsule rupture. Second, failure to optimally adjust machine parameters so as to facilitate efficient surgery will result in the surgeon having to compensate by more frequent and exaggerated manual maneuvers that can increase the possibility of tissue damage. Although some surgical complications are inevitable by-products of preexisting anatomy, many can be avoided by judiciously examining the relationship of the machine technology and the fundamentals of the microsurgical techniques to modern phaco surgical methods. Many aspects of the machine technology’s contribution to surgical complications can be understood by first simplifying the role that the machine plays in a routine case. That role is to create and maintain a fluidic circuit that starts at the elevated irrigating bottle, passes through the eye and then the phaco pump, before draining into a collection chamber.

If a cataract has a soft, gel-like density, then the nuclear material can propagate along the fluidic circuit as the phaco needle’s aspiration port is placed against the nucleus, aspirating it. As the nuclear density increases, the pump must create more vacuum to deform the nuclear material sufficiently for aspiration. If the nucleus has still greater, crystallinetype density, then an appropriate amount of ultrasound must be titrated so that the material can be emulsified sufficiently to allow pump vacuum and flow to deform it into and through the phaco needle

194 and aspiration line. The ultrasonic vibrating phaco

needle tends to push material away from it. During sculpting, the nucleus is held in place by capsule and zonules, but during carouseling emulsification of cracked or chopped fragments, fluidic parameters of vacuum, flow, and bottle height must be adjusted to counteract the ultrasonic repulsion so as to aspirate the nuclear material into the phaco needle.

The anterior chamber must be maintained during all phases of cataract surgery; its fluid pressure must therefore be greater than ambient atmospheric pressure. Any vacuum created in the fluidic circuit by the pump is optimally located between the aspiration port and the pump; any vacuum (pressure lower than atmospheric pressure) in the eye portion of the fluidic circuit would result in a chamber collapse, leading in turn to potential damage to the capsule, zonules, and corneal endothelium. One of the main determinants of intraocular pressure (IOP) is the height of the irrigating bottle, which yields an IOP of 11 mm Hg (above ambient atmospheric pressure) for every 15 cm (6 inches) of elevation above the eye. This relationship is accurate for hydrostatic pressures in pedal position 1. In pedal positions 2 and 3 IOP decreases (but remains greater than atmospheric pressure) with induced flow in proportion to the commanded pump strength, as well as the degree of aspiration port occlusion.

A potential for chamber collapse may occur if a surgeon uses a standard bottle height for most cases but neglects to appropriately raise it if the flow rate is subsequently increased to enhance followability. The converse is also true. For example, a surgeon may lower the bottle height to achieve a lower IOP for such conditions as weak zonules or a posterior capsule rent. However, a chamber collapse may occur if

the flow rate is not correspondingly adjusted to a lower setting that is appropriate for the lower bottle height. Once again, bottle height must be titrated not only for hydrostatic pressures in pedal position 1 but also hydrodynamically to a given pump strength for positions 2 and 3. Needless to say, the highest elevation of the bottle will be inadequate if the irrigating fluid is completely depleted; operating room staff vigilance is required in this area for longer cases. The potential for this problem is increased if the surgeon has the room lights dimmed partly or completely during cataract surgery.

PUMP TYPES

To create vacuum, a pump of some type is necessary. Classically, pumps have fallen into two categories. The flow pump, the best example being a peristaltic pump, allows the surgeon to control both flow and vacuum parameters. The vacuum pump, for example the Venturi pump, allows surgeon control over vacuum only. The amount of flow is dependent on the vacuum setting and cannot be set by the surgeon. Recently, pumps have evolved such that flow pumps are so responsive they can be programmed to respond as if they were vacuum pumps. Additionally vacuum pumps can be manipulated to act as if they were flow pumps. These modern pumps are therefore named “hybrid pumps.”

Irrespective of pump selection, flow, measured in cubic centimeters per minute, (cc/min) is the force that brings material toward the phaco tip. In general, the higher the flow, the faster events will occur within the anterior chamber. Vacuum setting, measured in millimeters of mercury (mm Hg), will hold material on the phaco tip, once occlusion has occurred.

FLUIDIC COMPLICATIONS—

FLOW MANAGEMENT

As discussed above, flow rate (cc/min) is an important factor in determining IOP. Flow rate can be increased directly on a flow pump by increasing the commanded flow rate or indirectly on a vacuum pump by increasing the commanded vacuum; in both cases, the actual flow rate is dependent on the degree of aspiration port occlusion. The actual flow rate is also affected by the fluidic circuit’s resistance, which is in turn determined by the internal diameters of the phaco needle as well as the (especially aspiration line) fluidic tubing. In addition, flow rate is affected proportionately by bottle height, but only when using a vacuum-priority pump. One potential arrangement, which may lead to complications, is to use a vacuum-priority pump for a high-vacuum tech-

nique. A high commanded vacuum setting produces a high flow rate with the unoccluded phaco tip. The surgeon may compensate for this with an elevated bottle height to maintain adequate IOP in the face of the high flow rate. However, the higher bottle height produces an even higher flow rate that not only diminishes the effectiveness of increasing the IOP, but also produces potentially dangerously fast intraocular currents that can uncontrollably attract and incarcerate unwanted material such as iris and capsule.

The induced flow rate from a high commanded vacuum can be lowered to a safer level by the use of a high-resistance phaco needle with a small internal diameter, such as a MicroFlow or MicroSeal needle. In addition, the surgeon should titrate the amount of commanded vacuum during phaco with linear pedal control according to the clinical application and the status of the aspiration port. Appropriately high vacuum may be used safely when the aspiration port is occluded, for example, when gripping a heminucleus in preparation for chopping. However, when anticipating an occlusion break at the end of a chop or during carouseling ultrasonic emulsification, the surgeon should linearly titrate vacuum to a lower, safer, and more appropriate level.

ASPIRATION LINE OBSTRUCTION

Another potential area of complication related to IOP maintenance and flow concerns is the presence of an obstruction between the aspiration port and the pump. Although kinked aspiration line tubing can produce this effect, it is most often caused by the localized accumulation of nuclear emulsate, clogging the aspiration line, especially when sculpting dense, mature cataracts. This type of obstruction can significantly impair the effectiveness of the phaco machine by limiting the pump’s ability to transfer its force (either via flow or vacuum) past the obstruction to the phaco tip where it is needed. The surgeon can recognize this problem when free (e.g., chopped) nuclear fragments fail to be effectively drawn to the phaco tip when in pedal position 2 and using a flow setting that usually is effective in this situation. Similarly, an aspiration line obstruction is suspected when faced with insufficient grip of an occluding nuclear fragment when using a vacuum setting that usually achieves a good grip. An aspiration line clog is also a strong possibility when observing intraocular flocculence (“lens milk” or “phaco dust”) during sculpting, indicating the inability for pump-induced flow to effectively clear the anterior chamber of the ultrasonically induced emulsate.

Any of these scenarios must prompt the surgeon to interrupt the surgery so that the problem can be iso-