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Main Issue March 2009

Pearls for the Visco-Shell Technique

This technique facilitates phacoemulsification of the morgagnian cataract.

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A morgagnian cataract is a hypermature lens with a completely liquefied cortex. In these cataracts, the dense nucleus sinks inferiorly.1 In addition to causing remarkable visual impairment, serious sequelae, such as phacolysis, may result. Phacolysis breaks down the hypermature cataract, causing an antigenic reaction to the lens proteins released into the anterior chamber. The end result is severe inflammation. When paired with a long history of secondary glaucoma, phacolysis may cause irreversible visual damage.

To prevent such situations, morgagnian cataracts must be removed as soon as possible; however, surgeons often hesitate to perform phacoemulsification in these circumstances because it demands a high degree of skill and considerable experience. The fluctuating anterior capsule complicates creation of the continuous curvilinear capsulorrhexis (CCC), and lack of an epinucleus and cortex can result in a high rate of posterior capsule rupture during phacoemulsification.

Sodium hyaluronate 2.3% (Healon5; Advanced Medical Optics, Inc., Santa Ana, California) is a viscoadaptive ophthalmic viscosurgical device (OVD) that acts as a viscous, cohesive agent at low flow rates and as a pseudodispersive agent at higher flow rates.2-4 Use of Healon5 alone or in combination with the soft-shell technique preserves anterior chamber depth during creation of the CCC.3,4 Based on the characteristics of Healon5, I developed a technique to wrap the hard nucleus of the morgagnian cataract into a visco-shell for safe and effective phacoemulsification.

SURGICAL TECHNIQUE
It is important to perform phacoemulsification with proper fluidics settings and within the middle of the Healon5 visco-shell. In this article, I describe the method to create the visco-shell (Figure 1A through 1D).

First, Healon5 is injected into the anterior chamber as well as between the nucleus and the posterior capsule. An ample amount of Healon5 is injected above and beneath the nucleus so that the nucleus is stabilized without significant movement during phacoemulsification. Under lowered fluidics, phacoemulsification is performed within the visco-shell, which will retain its original form.

Figure 1E through 1M illustrates the surgical sequence in a typical morgagnian cataract eye. After topical anesthesia (ie, lidocaine HCl 4%), a conjunctival peritomy is made at the upper limbus. A bipolar coagulator tip is applied, blanching the exposed episcleral vessels. With a microkeratome, scleral pocket dissection is initiated approximately 1 mm behind the limbus.

A sideport incision is made with a 20-gauge microvitreoretinal knife. Subsequently, the soft-shell technique5 is initiated: After the anterior chamber is filled with Healon5, approximately 0.1 mL of trypan blue is injected under the OVD.

A 5-mm CCC is created with capsulorrhexis forceps. Because the liquefied cortex flows from the capsular bag during capsulorrhexis, hydrodissection is unnecessary, and the intracapsular color changes from white to brown instantly. Prior to phacoemulsification, Healon5 is gently injected between the lens nucleus and the posterior capsule to lift the entire nucleus and expand the capsular bag (Healon5 visco-shell technique). The nucleus is slightly subluxated out of the bag, and Healon5 is also injected between the cornea and nucleus to protect the corneal endothelium.

At this point, the nucleus is wrapped within the visco-shell, and therefore it is stabilized. Phacoemulsification is performed with lowered fluidics parameters (aspiration flow rate, 20 cc/min; phaco power, 70%; bottle height, 80 cm). With the phaco-chop technique,6 the nucleus is divided into fragments and removed. With scrupulous care, all the manipulation at this phase is performed in the middle of the visco-shell. Intracameral stability is extremely good.

After phacoemulsification, the OVD is injected into the anterior chamber, and a foldable acrylic IOL is implanted into the capsular bag. Using the two-compartment technique,7 the OVD is completely aspirated from both the capsular bag and the anterior chamber. Finally, a bipolar coagulator tip is applied to produce coagulation of the incised conjunctiva. One day after surgery, no postoperative complications were found. Postoperatively, topical diclofenac and levofloxacin are applied four times daily for 4 weeks.

CHOICE OF OVDS
The timing of the OVD injection is important. Due to the total liquefaction of the cortex, the hard and dense nucleus of the morgagnian cataract easily moves around within the anterior chamber during cataract surgery. Thus, phacoemulsification entails a higher risk of corneal endothelial damage, posterior capsular rupture, and nuclear displacement into the vitreous. The appropriate use of OVDs is highly effective in preventing such intraoperative complications. A viscoadaptive OVD is designed to change its behavior at flow rates of approximately 25 cc/min. Additionally, viscoadaptive OVDs have higher elasticity than other OVDs. Using proper flow parameters, a viscoadaptive OVD can act as a shell to wrap and sustain the dense nucleus of a morgagnian cataract, facilitating safer and more efficient phacoemulsification.

OTHER USABLE OVD
Sodium hyaluronate 1.65%, sodium chondroitin sulfate 4% (DiscoVisc; Alcon Laboratories, Inc.) is a viscous dispersive OVD reported to have an intermediate cohesive/dispersive index, facilitating space maintenance and tissue protection.8 A cataract surgery simulation study in porcine eyes demonstrated that, compared with Healon5, DiscoVisc was better retained during phacoemulsification and more easily removed after IOL implantation.9 Another simulation study found that DiscoVisc was closest to the ideal OVD because it remained in the eye when necessary and was easy to remove at the end of surgery.10 Based on these reports, DiscoVisc may be an appropriate substitute for Healon5 in the visco-shell technique.

APPLICATION TO OTHER CATARACT TYPES
The visco-shell technique may also be applied in various types of cataract, especially in rock-hard cataracts with no cortical materials. In a typical rock-hard cataractous eye, it is inappropriate to inject Healon5 under the entire nucleus before phacoemulsification because acute intraocular pressure elevation may cause complications, such as posterior capsule dehiscence followed by nuclear displacement into the vitreous cavity. In an eye with a large CCC and complete hydrodelineation, Healon5 may be injected at the early stage of phacoemulsification.

The visco-shell technique is highly effective in phacoemulsification of a morgagnian cataract. The nucleus is wrapped and well stabilized during the procedure. Proper fluidics settings are important to appropriately conduct the visco-shell technique using a viscoadaptive OVD. This technique may also be applied in rock-hard cataracts with no cortical materials.

Masaki Sato, MD, PhD, is an Associate Professor, Department of Ophthalmology, Mito Regional Medical Education Center, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan. Professor Sato states that he has no financial interest in the products or companies mentioned. He may be reached at tel/fax: +81 29 853 3148; e-mail: masasato@md.tsukuba.ac.jp.

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