Viscodissection reduces posterior capsular rupture during phaco

With otherwise identical technique, incidence of rupture was reduced in a large series of patients.

Issue: September 15, 2006

BySabrina Nicolich, BS

ByRichard Mackool Jr., MD

ByRichard J. Mackool Sr., MD

Hydrodissection is routinely performed in order to loosen the nucleus prior to phacoemulsification.

Richard J. Mackool

Viscodissection has been reported to reduce the risk of vitreous loss in eyes with posterior polar congenital cataracts and weak or deficient posterior capsules, to serve as an aid in the phacoemulsification of softer lenses by creating elevation of the nucleus and to act as a teaching tool that permits deep grooving of the nucleus.

One of us (Richard Mackool Jr., MD) theorized that viscodissection during phacoemulsification of routine cataracts might decrease the incidence of posterior capsular rupture by placing a thicker barrier between the capsule and lens, thereby preventing contact of instruments with the capsule. Because no previous studies have been reported, we designed and performed a prospective study of viscodissection during phacoemulsification.

We conducted a retrospective study to determine whether viscodissection using Viscoat (chondroitin sulfate, sodium hyaluronate, Alcon) performed after hydrodissection reduced the incidence of capsular rupture during phacoemulsification. The results were compared retrospectively to those obtained in patents undergoing phacoemulsification with hydrodissection only.

We found that viscodissection markedly decreased the incidence of posterior capsular rupture from 0.8% to 0.1%.

Methods

After performance of a circular capsulorrhexis, hydrodissection was performed in the axis perpendicular to the primary incision. For example, if a temporal clear corneal incision were made at the 9 o’clock position of the right eye, hydrodissection was performed at 12 o’clock and 6 o’clock.

In patients undergoing viscodissection, injection of Viscoat was then performed opposite the primary phaco incision immediately after hydrodissection. Approximately 0.15 cc of Viscoat was injected, using a side-to-side, sweeping motion for 180° (Figures 1 and 2). The viscoelastic was observed dissecting between the anterior capsule and cortex, as well as around the equator of the lens. In many cases it could also be seen passing beneath the nucleus, although the amount of posterior dissection was difficult to quantify.

All procedures were performed by one surgeon who had extensive experience in phacoemulsification. A previously reported technique was used for all procedures. In summary, the Alcon Infiniti Vision System was used to sculpt a central nuclear bowl, followed by horizontal chopping of the nucleus into multiple segments. Chopping was accomplished by impaling the nucleus using 250 mm Hg vacuum when the nucleus was of sufficient density. In eyes with softer lenses, manual chopping (no impaling) with the chopper and phaco tip was performed. Nuclear segments were then removed in standard fashion using a flow rate of 25-50 cc/min and maximum vacuum level of 250-750 mm Hg. Infusion bottle height was 130-140 cm. During removal of the last one or two nuclear segments, the chopper or a spatula was used to protect the posterior capsule from contact with the phaco tip.

Between Feb. 1 and Aug. 31, 2005 we developed the viscodissection technique by performing the procedure with different viscoelastics, varying the amount and area over which the injection was made. After standardizing the technique, 725 consecutive procedures were performed between Sept. 1, 2005 and Jan. 31, 2006.

A retrospective analysis was then performed by chart review of cases. The number of eyes experiencing posterior capsular rupture during phacoemulsification using only hydrodissection (the “control” group) was compared to the number of posterior capsular ruptures during phacoemulsification using hydrodissection and viscodissection. Eyes with pre-existing dislocated lenses, zonular disruption or pseudoexfoliation were excluded from the study.

Viscoat fills the capsular fornix (arrow) and dissects posteriorly to the region of the central posterior capsule.

Images: Mackool RJ

Viscoat is injected beneath the anterior capsule for approximately 180° (curved arrows).

Results

Seven hundred fifty-nine consecutive procedures using hydrodissection without viscodissection were performed. Posterior capsular openings occurred during phacoemulsification in six patients (0.8% of cases). Hydrodissection followed by viscodissection was performed in 725 consecutive patients. Posterior capsular rupture during phacoemulsification occurred in one patient (0.1% of cases). The difference in posterior capsular rupture rate between the two groups was significant at the 93% confidence level ( P < .07) using Fisher’s exact test.

Discussion

Hydrodelineation (injection of fluid between the nucleus and epinucleus) and hydrodissection (injection of fluid between nucleus and cortex and/or cortex and capsule) are commonly performed during phacoemulsification. Viscodissection (injection of viscoelastic material between capsule and cortex) has been recommended as a technique to prevent posterior dislocation of lens material and anterior prolapse of vitreous during phacoemulsification performed on eyes with congenital posterior polar cataracts because they may have a posterior capsular defect.

It was theorized that routine viscodissection might reduce the incidence of posterior capsular rupture during phacoemulsification by creating a barrier that would prevent inadvertent contact of the posterior capsule with the phaco tip or other instruments. We initially performed viscodissection with several viscoelastics and elected to perform the current study with Viscoat because it tends to resist aspiration and therefore remain in situ. The surgical technique (other than viscodissection) did not change during the course of the study, and a large sample was used.

Our results indicate that viscodissection with Viscoat significantly reduced the incidence of posterior capsular rupture during phacoemulsification. Because other variables did not change, it is our belief that viscodissection with chondroitin sulfate was the causative factor in the reduction of posterior capsular rupture.

Possible mechanisms for this beneficial effect include the creation of a buffer zone between instruments and the posterior capsule, including the equatorial region of the capsule opposite the phacoemulsification incision, with the viscoelastic also acting to physically prevent movement of the capsule toward the phaco tip during the procedure. Another possible mechanism is lubrication of the phaco chopping instrument. The latter is repetitively moved through the region of viscoelastic injection during the horizontal chopping technique, and chondroitin sulfate may therefore lubricate the tip. Should the chopper be dragged over the capsule, the lubrication may reduce the risk of posterior capsular rupture.

A weakness of this study is that patients in each group were operated consecutively and were therefore not randomly assigned to receive either hydrodissection alone or hydrodissection and viscodissection.

For more information:

Richard J. Mackool, MD, Richard Mackool Jr., MD, and Sabrina Nicolich, BS, can be reached at the Mackool Eye Institute, 31-27 41st St., Astoria, NY 11103; 718-728-3400; fax: 718-728-4882; e-mail: mackooleye@aol.com.

References:

Allen D, Wood C. Minimizing risk to the capsule during surgery for posterior polar cataract. J Cataract Refract Surg. 2002;28(5):742-744.

De Luise VP. Viscodissection as an adjunct to phacoemulsification. Ophthalmic Surg. 1988;19(9):682.

Hosny M, Eldin SG, Hosny H. Fluorescein-assisted viscodissection for easier phacoemulsification. Int Ophthalmol. 2001;24(5):257-258.

Mackool RJ. Personal phacoemulsification technique. In: Phacoemulsification Principles and Techniques. Buratto L, Werner L, Zanini M, Apple D, eds. Thorofare, N.J.: SLACK Inc.; 2003:363-376.