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High-viscosity OVD helpful in microincision cataract surgery
The ophthalmic viscosurgical device aids in chamber stability and corneal protection.
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The evolution of cataract surgery has bestowed a significant improvement in visual quality following surgery, a quick postoperative recovery and return to normal lifestyle activities, and, for the most part, a painless surgical procedure that our patients have come to enjoy and expect from their operating surgeons. The bar for cataract surgery has clearly been raised.
As important as the ocular surface is to visual quality, so is the choice of ophthalmic viscosurgical device (OVD) and operative wound size for optimal phacoemulsification and IOL implantation. Wound size continues to shrink with modern-day microincision cataract surgery (MICS) using all of the leading phacoemulsification platforms, and this change in surgical focus has negated, for the most part, iatrogenically induced astigmatism and offers better wound stability. In addition, a well-sealed microincision would obstruct and prevent harmful ocular surface bacteria from gaining access to the anterior chamber. Once inside the eye during the phacoemulsification procedure, two important aspects include protecting the corneal endothelium and maintaining anterior segment stability, such that unwanted tissue damage to the iris, lens and cornea can be prevented or minimized. There is a continued emphasis on IOL technology to keep pace with the shrinking surgical wound size, such that there is no need to expand the initial corneal wound to permit safe IOL implantation.
In this column, Rosa Braga-Mele, MD, FRCSC, an OSN Cataract Surgery Board Member, describes the surgical steps in modern coaxial MICS and the preferred OVDs for improved postoperative surgical outcomes.
Thomas John, MD
OSN Surgical Maneuvers Editor
Modern coaxial MICS is described as any coaxial surgical procedure that can be performed with an incision of 2.4 mm or less. This small-incision surgery aids in increased anterior chamber stability and reduces complications. Creating less traumatic, astigmatically neutral incisions also helps get patients closer to their refractive target and results in improved visual outcomes. Because smaller wounds seal tightly, potentially less leakage results postoperatively and the risk for endophthalmitis is lower.
OVDs are essential tools for MICS, as with any phaco procedure. Using the high-viscosity OVD Healon GV (sodium hyaluronate 1.4%, Abbott Medical Optics) enables surgeons to achieve good space maintenance in the anterior chamber in the majority of MICS cases and also provides the necessary corneal protection.
Rosa Braga-Mele
Several platforms can be used for the coaxial MICS procedure, including the WhiteStar Signature for 2.4-mm incision surgery with implantation of the Tecnis IOL (both AMO) and the Infiniti Vision System with OZil IP with implantation of the AcrySof IQ, toric and ReSTOR portfolios (all Alcon) through a 2.2-mm incision.
With smaller-incision surgery, surgeons are looking for a more controlled system that has fluidic advantages to minimize the amount of turbulence within the anterior segment. This results in a quieter eye with crisp vision 1 day postop. Studies, such as those by Masket, show that with a smaller 2.2-mm incision, surgically induced astigmatism is reduced compared with larger coaxial cataract surgery incisions. This is especially important in the area of presbyopia-correcting IOLs or refractive IOLs because the less astigmatism that is induced, the better the visual outcomes. Additionally, MICS has a reduced risk of endophthalmitis and other postop complications due to the smaller incision size.
Surgical procedure
To begin MICS, I use a side-port incision that is either 0.7 mm or 0.9 mm in size. I then inject an intracameral non-preserved lidocaine and phenylephrine cocktail through the side port, which allows for anesthesia and pupil dilation. I tend not to insert an OVD at this time because, with MICS procedures, I find better control of making the initial keratome incision. For an incision that is 2.2 mm or 2.4 mm in size, I proceed using a bevel-up keratome (Figure 1), which I find to be better than a double bevel at producing a good two-step wound. Therefore, I make the incision in a two-step fashion without any OVD in the eye. Then, for the majority of my cases, I use a cohesive OVD. Available options include Healon GV, Healon5 (sodium hyaluronate 2.3%, AMO), DuoVisc (1% sodium hyaluronate and 3% sodium hyaluronate, 4% chondroitin sulfate, Alcon), DiscoVisc (4% sodium chondroitin sulfate, 1.65% sodium hyaluronate, Alcon) and AmVisc (sodium hyaluronate 1.2%, Bausch + Lomb). I prefer Healon GV, which I believe to be one of the gold standards in OVDs and excellent for most standard phaco cases. It allows good space maintenance in the anterior chamber and also provides the necessary corneal protection. It is a cohesive OVD that also has some dispersive properties, and removal is relatively easy.
I then perform my capsulorrhexis, hydrodissection and phacoemulsification as in routine cases with a microincision system. It is important to note that with these 2.2-mm or 2.4-mm incisions, surgeons do not need to change any of their techniques. Because everything is exactly the same, no new instrumentation is required and the surgeon’s procedure does not vary. There are not even any changes needed to the surgeon’s fluidic parameters with both the WhiteStar Signature and the Infiniti with OZil IP.
Figure 1. Using a bevel-up keratome, the incision is made in a two-step fashion without any OVD in the eye.
Images: Braga-Mele R
Figure 2. The OVD is removed by rock and rolling the IOL to get the OVD from behind the lens.
Next, after cortex removal, I put the OVD into the bag and then insert the IOL using a modified wound-assist technique. (For the 2.2-mm and the 2.4-mm incision, I place the inserter just within the lip of the wound so it is a modified wound-assist procedure for IOL implantation.) Then I remove the OVD by rock and rolling the IOL to get the OVD from behind the lens (Figure 2). I finish by hydrating the wound and having a formed, controlled chamber.
Additional pearls
In most MICS cases, I use Healon GV. However, I use a different OVD in some microincision or general cases. For instance, in patients with small anterior chambers, I will use a combination of Healon GV and Healon5. I layer the Healon5 over the iris and put a dollop of Healon GV in the center to help keep back the iris and maintain the chamber. I find that because Healon5 is a viscoadaptive agent, it is excellent at maintaining the chamber and controlling the iris during surgical procedures.
In cases in which there are any corneal endothelial abnormalities, such as guttata or Fuchs’ corneal dystrophy, I use a combination of Healon GV and Healon EndoCoat (sodium hyaluronate 3%, AMO) or Viscoat (4% chondroitin sulfate, 3% sodium hyaluronate, Alcon). I use the EndoCoat or Viscoat, both dispersive OVDs, to coat the corneal endothelium, and then I use Healon GV in the center of the eye in a soft shell technique, as described by Arshinoff.
Conclusion
Coaxial MICS is a key procedure in a surgeon’s armamentarium today, and it will continue to be an evolving and important part of modern cataract surgery. The use of OVDs aids surgeons in maintaining a quiet and stable eye and helping patients achieve the best visual outcomes possible.