The hydrosteps are a significant but often overlooked portion of the phacosurgical procedure. Although hydrodelineation is straightforward, hydrodissection is associated with complications that can compromise the patient's zonular structure and capsular bag.
CAUSATIVE FACTORS OF COMPLICATIONSConventional Hydrodissection
If the surgeon fails to place the irrigating cannula far enough peripherally, hydrodissection will occur between the layers of cortex, and a dense layer of cortex will remain adherent to the posterior capsule. This situation places unnecessary stress on the zonules and possibly the ciliary body during I/A, and it will extend the time required for I/A. In the presence of a torn posterior capsule, traction on the capsular bag can enlarge the rent and/or rupture the vitreous face. The technique described here is termed conventional hydrodissection.
Errant Placement of the Cannula
Although unusual, it is possible inadvertently to place the irrigating cannula beneath the iris, but on top of the anterior capsule. As a result, fluid is injected within the zonules, over the vitreous face, and into the posterior capsule. The fluid will cause the anterior chamber to become shallow, as occurs with a fluid misdirection syndrome. This situation most often occurs in the presence of small pupils.
Incomplete Hydrodissection
If the irrigating fluid does not pass completely around the epinucleus and cortex, some of this material will remain attached to the capsular bag (Figure 1). The lens will therefore not rotate freely, and attempting rotation may (1) stretch or tear the zonules or (2) create a rent in the capsular bag. In cases of pre-existent zonular weakness, the problem is magnified.
Additionally, without adequate cortical cleavage, epinuclear and cortical remnants usually adhere to the capsular bag at the equator. When the surgeon performs phacoemulsification and pursues the equatorial material, he may accidentally aspirate the equatorial bag while in the process of aspirating epinucleus and cortex adhering to the capsular bag. That action can disrupt the zonules, may lead the surgeon to phaco through the equatorial bag, and may tear the posterior capsule.
A Small Capsulorhexis and a Large Nucleus
In patients with large nuclei, creating a small capsulorhexis can result in capsular block (Figure 2). When the surgeon injects fluid beneath the anterior capsule and behind the nucleus, the vector forces created by the large nucleus and small capsulorhexis cause the nucleus to float forward and block the egress of fluid around or underneath the anterior capsule. The fluid builds up quickly within the capsular bag and causes it to blow out either anteriorly or posteriorly, depending on where the weakest point of the capsule is located.
Similarly, rapidly injecting a large amount of hydrodissecting fluid, even in the presence of a smaller, softer nucleus, can cause fluid to accumulate so quickly that a relative pupillary block occurs and, again, tears the capsule.
AVOIDANCE PEARLSCortical Cleaving Hydrodissection
There are several reasons to switch from conventional hydrodissection to cortical cleaving hydrodissection (Figure 3). The latter technique is performed peripherally in order to cleave cortex from the capsular bag, a situation that allows the entire endonucleus, epinucleus, and cortical complex to rotate freely within the bag. The surgeon then separates the endonucleus from the epinucleus and cortex via hydrodelineation. This step permits a two-procedure phacoemulsification. First, the surgeon emulsifies the endonucleus. If performed with a protective shell of epinucleus, this process will prevent sharp fragments (particularly an issue with hard nuclei) from tearing the posterior capsule during potential surge. Next, the surgeon removes the epinucleus and cortex using lower settings to minimize surge, to remove the material more completely, and to minimize the need for I/A.
In the presence of a torn posterior capsule, cortical cleaving hydrodissection facilitates the removal of cortex without enlarging the tear because the cortex adheres less to the capsular bag. If the patient's zonules are weak, cortical cleaving hydrodissection eases the removal of the epinucleus and cortex and avoids both tearing more zonules and disrupting the capsular bag. The complications of both forms of hydrodissection are similar.
Additional Tips
To avoid accidentally placing the irrigating cannula on top of the anterior capsule, the surgeon should carefully watch the instrument's progression to ensure that it passes below the capsule, particularly in the presence of small pupils.
If the nucleus is large and hard, it is sensible to create a larger capsulorhexis (eg, 5.50 to 5.75 mm) and use a 6.00-mm lens implant, rather than make a 4.00-mm capsulorhexis. If the capsulorhexis created is too small, enlarging it prior to performing hydrodissection can avert the potential problem of capsular block. The surgeon may need to use a vital stain of the anterior capsule to extend the capsulorhexis. Additionally, he should judiciously perform hydrodissection behind the nucleus. It is important to watch the fluid wave to ensure that excessive amounts of fluid do not build behind the nucleus, a situation that can cause capsular block.
MANAGEMENT ADVICEErrant Fluid Injection
When a misplaced cannula injects fluid over the anterior capsule so that it fills the space between the vitreous face and lens nucleus, the surgeon will notice the problem as the anterior chamber suddenly becomes shallow and the lens, capsule, and iris move anteriorly. At this point, he must determine whether a suprachoroidal effusion/hemorrhage or a variant of a fluid misdirection syndrome has occurred. First, he should halt the procedure and feel the globe in order to ascertain its firmness. Generally, the globe will be firm due to the presence of excess fluid in the vitreous. The next step is to decompress the anterior chamber slightly and wait 5 to 10 minutes. If the globe remains firm, then it probably has suffered a choroidal effusion or hemorrhage. With a variant of a fluid misdirection syndrome, the fluid will regain equilibrium within the eye during the waiting period. Once the eye has stabilized, the surgeon again performs careful hydrodissection while the cannula is properly positioned.
A vitreous tap is an alternative to the waiting period and may also be appropriate for a case in which the eye has not softened adequately but the surgeon strongly suspects fluid misdirection. To perform the tap, the surgeon uses an MVR blade to make a small stab incision through the pars plana 3.0 to 3.5 mm posterior to the limbus. Next, he uses a 27-gauge cannula to gently withdraw between 0.1 and 0.3 cc of liquid vitreous. If the eye becomes firm again after the tap, there is probably a suprachoroidal hemorrhage.
Obviously, the surgeon is free at any point to use an indirect ophthalmoscope to examine the retina for a choroidal effusion or hemorrhage. An alternative is to use the handheld lens created by Robert Osher, MD, of Cincinnati (Osher 78 D Maxfield; Ocular Instruments, Bellevue, WA).
Adherent Epinucleus and CortexThe endpoint of cortical cleaving hydrodissection is that the surgeon sees the fluid wave pass behind the entire nucleus to the opposite side. When the nucleus rises within the capsular bag, it indicates that fluid is collecting behind the lens. The surgeon then presses down on the nucleus to force the fluid trapped behind it to travel around the equator, thereby lysing all peripheral cortical-nuclear connections. He applies this pressure first on one side of the nucleus and then again in a location 180º opposite. These steps should ensure a freely rotating nucleus. If the nucleus does not turn freely, then the hydrodissection was incomplete, and the surgeon should repeat the procedure.
If repeated or full hydrodissection is impossible, the surgeon must exercise greater care during phacoemulsification so as not to stress the zonules or approach the equatorial cortical material too closely. A nick in the anterior capsule or a discontinuous capsulorhexis (eg, one that extended toward the equator and had to be finished from the other side) are good reasons not to complete hydrodissection. The addition of too much fluid will cause a capsular tear that extends to the equator or, worse, into the posterior capsule. Another reason surgeons might hesitate to complete hydrodissection is poor visualization due to a small pupil. Additionally, some might forego complete dissection in cases of pre-existing weak zonules caused by earlier zonular trauma, zonular tears, or pseudoexfoliation. Although it is difficult to hydrodissect and fully rotate the nucleus in these cases, I believe they actually require extra hydrodissection. If the surgeon can continue to work carefully until the nucleus is completely free within the capsular bag, then emulsifying the endonucleus, epinucleus, and cortex will be easier and less likely to further damage the zonules.
A Torn Capsule
Whether caused by incomplete hydrodissection leading to a torn equatorial bag, a discontinuous capsulorhexis, or a capsular block, the end result may be a torn capsule. The surgeon must then choose whether to convert to extracapsular surgery or to complete the case with phacoemulsification. The decision depends on his level of comfort when performing phacoemulsification in the presence of a torn capsule.
In this situation, many surgeons use a dispersive viscoelastic (Viscoat; Alcon Laboratories, Inc.) to elevate the nucleus to the level of the iris, close the phaco wound, and open an extracapsular wound through which to deliver the nucleus. I prefer to continue with phacoemulsification. First, I inject a dispersive viscoelastic behind the nucleus in order to secure it and over the nucleus to protect the endothelium. I call this maneuver a Viscoat sandwich. If I believe that the posterior capsule has blown out due to a posterior capsular block, I often enlarge the anterior capsulotomy so that I may float the nucleus up to the level of the iris. I emulsify the nucleus over a Sheets Glide. I try to keep the nucleus in one piece and emulsify it with a carousel technique.
CONCLUSION
Often overlooked as an important prerequisite to successful phacoemulsification, the hydrosteps are vitally important. When performed well, good cortical cleavage will make the entire phacoemulsification procedure safer and more efficient. It will also shorten the time needed for I/A and increase its safety. Finally, in the presence of a torn posterior capsule, thorough cortical cleavage will facilitate the removal of residual cortex without placing additional stress on the damaged capsule.
An awareness of the fundamentals of hydrodissection and the gentle, cautious performance of the procedure can avert complications. It is well worth the time and effort to master this technique.
William J. Fishkind, MD, FACS, is Codirector of the Fishkind and Bakewell Eye Care and Surgery Center in Tucson, Arizona, and a clinical professor of ophthalmology at the University of Utah in Salt Lake City. He holds no financial interest in any products mentioned herein, but he is the editor of Complications in Phacoemulsification: Avoidance, Recognition, and Management, published by Thieme Medical Publishers. Dr. Fishkind may be reached at (520) 293-6740; wfishkind@earthlink.net.
