New OVD strategies for toric IOL implantation

“Once I insert
the lens into the
bag and achieve
its proper align ment, it stays
in place
”
David M. Kwiat, M.D.


“This technique
has greatly
improved my
post-operative
results
”
Richard Burns, M.D.

Premium lenses, such as an AcrySof IQ Toric, placed inside a bag of BSS can unfold faster and see less rotational forces due to
the decreased need for OVD removal from the bag

As the popularity of toric IOLs continues to grow, so does the pool of surgeon brainpower working on innovative ways to make implantation as efficient as it is safe. One area of interest has been the rotation of the implant beyond the desired final axis that can occur as viscoelastic is removed from the eye at the conclusion of the procedure. To help ensure the IOL ends up at the intended axis, some surgeons initially place it as far as 30 degrees shy of the desired location. Others use a second instrument through the sideport incision to hold the IOL in place while removing the OVD. In cases where the lens does over-rotate, the surgeon must spin it nearly an additional 360 degrees. Recently, several surgeons have been devising strategies that keep the lens in the desired position without the need for extra maneuvers.
David V. Leaming, M.D., Palm Springs, Calif., devised what he calls the snowman technique. Originally, the technique involved“building a snowman” out of three balls of DisCoVisc OVD (sodium chondroitin sulfate, sodium hyaluronate, Alcon, Fort Worth, Texas) stacked from the capsular bag to the anterior chamber and then to the wound. He later modified the technique based on the ultimate soft shell approach of Steve Arshinoff, M.D., clinical instructor of ophthalmology, University of Toronto, in which the surgeon seals off the capsulorhexis with viscoelastic and fills the capsular bag with balanced salt solution. Dr. Leaming found replacing the viscoelastic at the base of the snow man with BSS solution (Alcon) allowed the IOL to unfold more quickly. In addition, because the BSS solution, not viscoelastic, is removed from the bag at the end of the case, the IOL remains in place.

Modified snowman technique

Around the same time, Richard Burns, M.D., California Eye Professionals, Temecula, Calif., was also looking for ways to keep toric IOLs stable during OVD removal. He adopted the snowman technique but, thinking along the lines of “less is more,” he made modifications. He begins by placing a small amount of Viscoat OVD (sodium chondroitin sulfate, sodium hyaluronate, Alcon) at the entrance of the temporal corneal wound. “I don’t put any in the bag. I use just enough so I see it goes through to approximately a millimeter beyond the incision site.” Then, using a 27-gauge syringe through the paracentesis, Dr. Burns puts BSS solution into the anterior chamber so it slightly deepens the capsule. “The visco ‘plug’ at the temporal wound keeps the chamber intact,” he said. “I’m careful to put just a little BSS solution into the chamber so as not to force viscoelastic through the incision site.”
Next, Dr. Burns goes through the paracentesis to layer viscoelastic directly under the endothelium, keeping it entirely in the superior portion of the chamber. This pushes the BSS solution down into the bag a little deeper. “Once I see the bag deepen slightly, I stop putting the OVD into the chamber,” he said. “This is key. If I don’t put enough OVD in, the BSS solution does not push the bag open and there is no room to place the lens. If I put too much OVD in, it will blow out the plug and I will lose the chamber and/or OVD will enter the bag and displace the BSS. As you get used to it, it’s easy to see the BSS start to enter the bag.”
Dr. Burns then inserts the AcrySof IQ Toric IOL (Alcon) into the capsular bag, lining up the lens exactly with his pre-op corneal markings. “Because the lens is in BSS solution, it has a slight proclivity to rapidly open and sometimes invert, so I use a Sinskey hook to keep it level at the iris plane,” he explained. “Since there is very little viscoelastic in the chamber and none behind the implant, the lens stays where I put it, even after removing the OVD. It’s still in the same position the next day. This technique has greatly improved my post-operative results.” A study published in the February issue of the American Journal of Ophthalmology showed that using a dispersive OVD, as Dr. Burns does, rather than a cohesive OVD, provides greater rotational stability of the IOL during cataract surgery. 1 In the study, mean intra operative rotation of a single-piece hydrophobic acrylic IOL (model SA60AT or SA60NT, Alcon) was 7.42 degrees when Viscoat OVD was used, and 13.8 degrees when Healon GV (sodium hyaluronate, Abbott Medical Optics, Santa Ana, Calif.), a cohesive OVD, was used. During Viscoat removal, the IOL maintained alignment within 10 degrees in 70% of cases compared with 30% during Healon GV removal.

Helmet technique

David M. Kwiat, M.D., Kwiat Eye and Laser Surgery, Amsterdam, N.Y.,
tried several different techniques for implanting the AcrySof IQ Toric IOL but wanted to find a way to achieve optimal lens steadiness during OVD removal while maintaining anterior chamber stability and, therefore, safety. His solution is what he calls the helmet technique.
Once the nucleus and cortexare completely removed from the capsular bag, he fills the anterior chamber with DisCoVisc OVD at the iris plane and anterior. “This OVD provides the stability I need for the anterior chamber, but it can also be removed very efficiently,” he said. While filling the chamber with viscoelastic, Dr. Kwiat places the cannula at the anterior iris plane at a slight upward angle.
“Once the visco ‘helmet’ is in place, it effectively stabilizes the anterior chamber, fully protects the corneal endothelium, and seals the incision,” he said. Next, he fills the capsular bag with BSS solution. “At this point I have a very stable system. In other approaches, the presence of only BSS in the anterior chamber can cause collapse or shallowing with lens insertion, and the capsule can migrate anteriorly, increasing the risk for posterior capsular damage. With the helmet technique the visco helmet facilitates filling the bag with BSS because it directs all of the saline into the bag.” Dr. Kwiat also said it’s OK to see some migration of OVD toward the wound. The surgeon can use this as an endpoint and assurance that the bag is adequately inflated.
“Once I insert the lens into the bag and achieve its proper alignment it stays in place,” Dr. Kwiat said. “Since there is no need to insert the I/A tip behind the lens to remove any viscoelastic, I can finish the case without any need to manipulate the lens. One modification I have made is that I will at times gently irrigate the viscoelastic from the main incision with a cannula, which provides an alternative method for achieving removal with lens stablility.”
While Dr. Kwiat designed the helmet technique specifically for toric lens implantation, he now routinely uses it for all of his cases regardless of the type of implant. However, he may not use the technique when the capsular bag is stretched or unstable, or in some cases of pseudoexfoliation. “It’s a clinical decision that really depends on how the bag is behaving during surgery,” he explained.
For surgeons who want to use the modified snowman or helmet technique, both Drs. Kwiat and Burns recommended they try it first in a few non-toric cases. “That way you can focus on the process with out having to worry about aligning the lens at any particular orientation,” Dr. Kwiat said. Dr. Burns added, “With my technique there are subtle amounts of OVD used, so it helps if you figure that out first in a non-toric case. Once you do that a couple of times, you’ll be ready to go.”

Contact information

Burns: 951-296-9300; rburns9md@gmail.com
Kwiat: 518-265-1610; kwiatmd@yahoo.com

Reference

1. Joon Young Hyonab, Hwan Eok Yeoc. Rotational stability of a single-piece
hydrophobic acrylic intraocular lens dur ing removal of ophthalmic viscosurgical
devices. Am J Ophthalmol 2010;149(2):253-257.