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Dr. Kershner has no financial or proprietary interest in any of the devices or techniques described in this article.
Successful cataract surgery depends upon the latest techniques, state-of-the art instrumentation, and latest advances in viscoelastic technology. To maximize the benefits of the various available viscoelastics such as Healon (sodium hyaluronate 1%, Pharmacia), Healon GV (sodium hyaluronate 1.4%, Pharmacia), and Healon 5 (sodium hyaluronate 2.3%, Pharmacia), surgeons must know the differences in their behavior and their unique handling characteristics. When performing the demanding techniques of advanced microincision cataract surgery, which viscoelastic should the surgeon select? Is one viscoelastic better than the other? Is more than one required?
How can a surgeon differentiate between unsubstaniated marketing claims and fact and effectively apply the appropriate medium to the proper procedure? If surgeons understand the differences in the various products, they will be more effective in choosing the right one.
To better understand the products, I categorize them by their performance characteristics and divide them into three different groups: dispersive, cohesive, and adaptive.
Dispersive viscoelastics tend to be loose and, as the name describes, disperse easily inside the eye. Ocucoat (hydroxypropyl methylcellulose 2%, Bausch & Lomb) and Viscoat (chondroitin sulfate, sodium hyaluronate, Alcon) are dispersive viscoelastics.
Cohesive viscoelastics such as Healon and Healon GV are of greater molecular weight, uniformity, and complexity and, therefore, are more dense and tend to stick together inside the eye.
Adaptive viscoelastics (e.g., Healon 5) are the most recent addition to the viscoelastics market. As a very large molecule with a complex structure, the viscoadaptive Healon 5 has unique handling and intraocular properties. The large molecular chain allows the viscoadaptive agent to actually change its characteristics depending on the environment in which it is placed.
Why is a viscoadaptive valuable to surgeons? The viscosity of a substance such as Healon 5 allows it to change its characteristics when injected. It can behave like a viscodispersive in circumstances such as filling the capsular bag for IOL injection or it can act like a viscocohesive to separate tissue, such as for phaco tip insertion. In this fashion, it is adaptive, creating better control of tissues during surgery depending on the circumstances in which it is used. Healon 5 can control tissue positioning, is optically clear, and creates and maintains space within the eye, without breaking apart or washing out. As surgeons have recognized with other viscoelastic products, these substances must be completely removed at the conclusion of the surgery to avoid lingering effects on postoperative intraocular pressure .
A cataract surgeon can apply Healon 5 at any time from the start of surgery. First, the surgeon’s preferred incision is made. I prefer a 2.8-mm clear corneal incision placed on the steep meridian, which can neutralize preexisting astigmatism (BD Clear Corneal Incision System, BD Ophthalmic Systems, Waltham, Mass). If the cornea is astigmatically neutral, a plane parallel cataract incision can be made on a clear cornea. The ideal self-sealing incision architecture is an external arcuate incision, which approximates an internal rectangular configuration. The ratio of incision width to incision length should be 3:2. An incision should always accommodate the techniques and instruments being used.
Clinical experience with many viscoelastics has allowed me to chose Healon 5 for general use in cataract surgery. I do not reserve it for only difficult cases, such as narrow chambers or dense cataracts. When properly applied, Healon 5 performs well under the most common circumstances, as well as in the most challenging cases. Because Healon 5 remains in the anterior chamber to protect the endothelium during phacoemulsification, it provides excellent control for difficult cases.
Following are seven tips for maximizing the benefits of Healon 5 in cataract procedures.
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Tip #1: Facilitate Capsulorrhexis
Healon 5 deepens the anterior chamber for capsulorrhexis and reduces stress on the capsule and zonules (Slide 1).
By inserting Healon 5 onto the center of the lens capsule prior to making the capsulorrhexis, the anterior lens capsule can be
pushed posteriorly reducing stretch on the zonules. Because it occupies space efficiently, it is important not to overfill the
anterior chamber with Healon 5. Overfilling the eye makes instrument introduction, capsulorrhexis, hydrodissection, and IOL
insertion more difficult. With Healon 5 in place, the one-step capsulorrhexis forceps (Rhein Medical, Tampa, Fla) can be used
to open the capsule and conduct the tear with a single instrument (Slide 2).
Next, hydrodissection can be performed with a Binkhorst cannula and balanced salt solution irrigation just under the incision to loosen the cortical attachments from the lens capsule.
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Tip #2: Aid Phaco Tip Insertion
Insert Healon 5 under the incisional lip to aid in insertion of the phaco tip at the start of the phaco procedure (Slide 3).
Healon 5 occupies space, allowing passage of the tip without catching the iris, Descemet's membrane, or the incisional lip.
Tip #3: Protect During Phaco
The phacoemulsification should be contained within the triangle of safety. Insert Healon 5 into the center of the anterior chamber
during the phaco procedure to separate pieces and keep the cataractous lens in the iris plane and away from the corneal endothelium.
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Tip #4: Fill the Bag
Enlarge and expand the capsular bag for controlled IOL implantation. There are several ways to accomplish this. First, the surgeon
can fill the capsular bag with classic Healon. Then, place a bolus of Healon 5 in the center of the capsulorrhexis to expand the
opening and protect the cornea during IOL injection (Slide 4). I believe that Healon 5 should not be used exclusively to fill the bag.
It is important that there is sufficient space remaining to displace the viscoadaptive when the IOL is injected into the lens capsule.
I have found Healon 5 to be ideal in protecting intraocular tissues and for positioning the IOL during implantation. However, it should
be used sparingly.
Tip #5: IOL Insertion
Healon 5 can be used to control the IOL during implantation. Advances in lens designs make Healon 5 an efficient addition to
clear-cornea cataract surgery especially when implanting single-piece or three-piece silicone or acrylic lenses. Since the invention
of the IOL by Harold Ridley in 1949, we have seen numerous advances in IOL design. Pharmacia’s new 911A is a good example
of the latest design advances in the three-piece silicone IOL. This IOL can fixate within the capsular bag and may result in less
postoperative capsular fibrosis due to its unique square-edge optic design and capsular loop haptics. However, implantation of
the 911A may be more challenging because of its design and, therefore, is ideal for use with Healon 5.
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Tip #6: Inject the IOL
Healon 5 can be used to inject the IOL (Slide 5). Because fluids are noncompressible, inserting the IOL into an
overfilled capsular bag can be difficult. But, the viscoadaptive properties of Healon 5 can be advantageous in inserting the IOL.
The lens can be placed within the injector cartridge with Healon 5 allowing movement of the lens down the cartridge barrel without
friction or force.
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Tip #7: Remove Healon 5
Healon 5 must be completely removed after implantation of the IOL (Slide 6). Leaving any viscoelastic in the eye
after the conclusion of intraocular surgery can be associated with a postoperative pressure rise. The adaptive nature of Healon 5
makes removal simple. Because the viscoelastic sticks together, the irrigation and aspiration tip can remove the substance in
a single piece. The surgeon need not irrigate under the IOL or move the irrigation and aspiration tip to retrieve all of the viscoadaptive.
If surgeons select and apply viscoelastics wisely, the outcomes of microincision cataract surgery can be improved.
