All cataract surgeons use ophthalmic viscosurgical devices (OVDs) daily in surgery. Most of us run into problems occasionally.

In this article, I'll review the seven most common errors in viscoelastic use, and explain how to avoid them.

1. Poor injection: inappropriate filling of the target space

If we underfill the target space, usually the anterior chamber, the result is an underpressurized eye and viscoelastic floating in residual aqueous in the eye. An underpressurized anterior segment means that the posterior pressure caused by the constant pull of the extraocular muscles exceeds the pressure in the anterior chamber. The capsulorhexis will then tend to extend peripherally because it's performed on a convex anterior surface with pressure behind it. Injection of more viscoelastic equalizes the anterior and posterior pressure and permits a pressure-equalized capsulorhexis to be done with no tendency to extend peripherally.

Similarly, underfilling the capsular bag prior to intraocular lens (IOL) implantation results in wrinkles in the posterior capsule. These may catch on the unfolding IOL haptics, resulting in a posterior capsule tear.

On the other hand, if we overfill the target space with a lower viscosity OVD, we'll have viscoelastic leakage from the wound. If we overfill the target space with a higher viscosity agent, we may have overpressurization of the anterior chamber, or globs of OVD burping out when the wound is entered for a subsequent step. Anterior chamber overpressurization could result in posterior subluxation of the lens in cases of pseudoexfoliation, or other unstable conditions.

The solution to inappropriate filling is to fill the anterior chamber only through the primary incision, not the side port. Begin at the opposite angle of the anterior chamber, away from the incision, as you depress the wound lip to permit egress of aqueous while filling with OVD. You should use a large enough bore cannula to permit excellent tactile feedback sensation of the ocular inflation pressure, so that both visual and tactile filling are apparent.

2. Waiting too long before adding more OVD

Many situations have the potential to be disastrous when you delay stabilizing the anterior segment with more OVD. Don't wait to inject more OVD:

�         if the capsulorhexis begins to go astray

�         if the free flap of the capsulorhexis becomes tangled

�         if the iris is unintentionally frayed with the phaco tip

�         if a strand of vitreous strays into the field from around the lens equator

�         if a small hole is punched in the posterior capsule

�         if the anterior chamber appears filled with OVD, but the capsulorhexis rim isn't clearly delineated just prior to IOL implantation.

All of these circumstances (and I can think of more) are indicative of an unstable situation in the surgical field, and one of the best uses of OVDs is to stabilize. Surgical maneuvers are always easier in a viscoelastic-stabilized environment.

3. Getting tangled in viscoelastic

Sometimes a surgeon is unaccustomed to working in a high-viscosity environment. The surgeon, trying out a new super-viscous cohesive OVD, may unintentionally become tangled in viscoelastic. This usually occurs during performance of the capsulorhexis. You can prevent tangling of the capsulorhexis flap by dropping the grasped piece of capsule centrally, within the diameter of the rhexis, before releasing and attempting to regrasp the flap nearer to the tearing vertex.

When tangling occurs, you can correct it in two ways. First, you can inject more OVD, aiming at the tearing vertex of the capsule and pushing the flap to flatten it out. If that fails, you can flatten out the capsule by removing the OVD with the irrigation/aspiration (I/A) tip and subsequently refilling the anterior chamber with OVD.

The most important step, however, is to stop as soon as you sense that the flap isn't clearly visible, and perform the steps above. Otherwise you may extend the tear.

4. Failure to fill the capsular bag adequately with OVD before implanting the IOL

Sometimes, after I/A but before IOL implantation, the capsular bag won't fill easily when the OVD fills the anterior chamber. This is usually due to positive vitreous pressure and resultant collapse of the posterior capsule anteriorly against the anterior capsule and rhexis, obliterating the endocapsular potential space. Failure to observe this could result in implanting the IOL in front of the bag, or having the unfolding haptics catch on a fold in the rhexis or posterior capsule, tearing the rhexis or posterior capsule -- or both.

The solution to this problem is easy. Always inject the OVD into the center of the rhexis, at first horizontally to separate the bag from the cornea, then posteriorly, directly into the bag, to push the posterior capsule backwards and completely fill the bag. As you complete this, you'll see the capsulorhexis ring come forward and delineate beautifully. If you're careful to always fill the bag and deepen the anterior chamber in this deliberate fashion, incomplete filling of the bag will never occur.

5. Burping the OVD out of the wound

Sometimes we see higher viscosity cohesive OVDs burp out of the wound in a mass. Many surgeons see the burping out as a sign of OVD inadequacy. These surgeons don't like this because they don't understand what is happening.

We know that lower viscosity dispersives are easily diluted by balanced salt solution (BSS). Consequently, the dispersives leak out with the BSS, but we don't notice the loss of OVD because it's gradual and smooth. With a higher viscosity cohesive OVD, this dilution and leakage doesn't occur. Instead, one of two things can occur.

�         The irrigation of BSS can remain beneath the OVD mass. In this case the BSS doesn't push the OVD mass around the eye, and the case proceeds uneventfully, without expelling OVD.

�         The irrigation can fall behind the OVD mass, causing it to move in the anterior chamber until it blocks fluid egress from the incision. As fluid infusion continues, the intraocular pressure (IOP) then increases until one of the following events takes place:

�        burping out of the OVD, if the incision is too large

�        displacement of the lens into the vitreous, in a case of pseudoexfoliation with impaired zonular support.

Neither of these events is desirable. You can prevent both by clearing an egress path for the BSS as the irrigation cannula enters the eye to perform hydrodissection. All you need to do is wiggle the cannula tip gradually from side to side in the incision, while slowly injecting BSS as the cannula enters the eye. You can easily observe the BSS egress.

6. Failure to ask for a second syringe of OVD

All of us try to be economical in surgery. However, ask for a second syringe if -- for some reason -- an extra injection of OVD is required early in the case, and there is barely enough or not enough OVD for use later in the procedure.

Too many times, surgeons try to save time and a few dollars by refusing a second syringe. This can result in having to fix a bigger problem later, sometimes requiring an additional surgical procedure, more time or more money for other devices (and more OVD). It also increases the risk of complications.

When in doubt, use more OVD to repressurize the eye. The rest of the case then becomes easy. It's better to finish the case quickly and uneventfully, and to return a 90% full syringe of OVD, than for your patient to suffer a serious problem.

7. Failure to completely remove the OVD

Once the case is completed, failure to remove the OVD completely can have a number of serious consequences:

�         A postoperative IOP spike may cause pain, possibly visual loss on a vascular or neurogenic basis, and pupillary sphincter infarction.

�         A capsulorhexis blockade syndrome may occur, with early postoperative myopia and possible secondary angle closure glaucoma.

�         Swelling of the OVD in the capsular bag may contribute to malpositioning of the IOL.

�         Retained OVD may increase the risk of postoperative intraocular infection.

Any one of these complications can be severe. However, you can easily avoid them with proper removal by using either the Rock 'n' Roll technique for OVD removal or the Two Compartment technique. (If you're unfamiliar with these techniques, see "For More Information,") Either one of these techniques is more effective than less organized methods of OVD removal.

All OVDs can cause these problems if left in the eye. You may recover from one of the first six sticky sins of OVD misuse, but leaving OVD in the eye in significant amounts is the seventh and probably the deadliest of these mistakes.

Steve Arshinoff, M.D., practices at Humber River Regional Hospital in Toronto, where he specializes in cataract and refractive surgery. He coined the viscoelastic terms "cohesive" and "dispersive."

For More Information

Arshinoff SA: Rock 'n' Roll Removal of Healon GV. Proceedings of the 7th annual National Ophthalmic Speakers Program (Ottawa, Canada, June 1996). Medicopea 1997.

Tetz MR, Holzer MP: Two Compartment Technique to Remove Ophthalmic Viscosurgical Devices. J Cataract Refractive Surgery 2000, 26: 641-643.