CATARACT/ IOL |
Understanding and learning the PAL technique by Maxine Lipner Senior EyeWorld Contributing Editor |
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Best method for rescuing a descending nucleus after capsular rupture  
With the PAL technique practitioners are able to rescue the nucleus before it descends posteriorially, bringing it forward into the anterior chamber when possible Source: David F. Chang, M.D.
In the stressful
situation of posterior capsular rupture, the Viscoat PAL (posterior
assisted levitation) technique can help surgeons to save the day.
When the posterior capsule ruptures while the nucleus is still present,
the surgeon’s immediate priority becomes extracting the
nucleus before it descends posteriorly, according to David F. Chang,
M.D., clinical professor, University of California, San Francisco. However, this often presents even very experienced surgeons with significant
challenges. “The pupil and the capsulorrhexis may be small, which
may have been contributing factors to the antecedent capsular rupture,
and the nucleus may have been divided into multiple smaller fragments,” Dr.
Chang said. “In addition, vitreous prolapse may block access to
the lens material and will become ensnared by the aspiration instruments.”
Keeping the nucleus from sinking is difficult. “Recognizing the
danger of chasing the nucleus with the phaco tip, most surgeons understand
the need to bring it forward into the anterior chamber if possible,” Dr.
Chang said. “However, this becomes very difficult if the nucleus
or the nuclear fragments have partially descended.” Dr. Chang explained. “Particularly
if the pupil or capsulorhexis diameters are small, the steep angle of
approach required by directing a cannula through the phaco incision may
make it very difficult to get an ophthalmic viscosurgical device [OVD]
behind the lens,” he said.
Posterior assisted
levitation techniques
The posterior assisted levitation technique, or “PAL,” solves
this problem by using a pars plan sclerotomy for instrument access. “Charles
Kelman, M.D., popularized this [PAL technique] using a cyclodialysis
spatula through the pars plana as a mechanical lever to lift a partially
descended nucleus up into the anterior chamber,” Dr. Chang said. “Richard
Packard, M.D. [London], advocated using a dispersive OVD, such as Viscoat
[chondroitin sulfate 4%/ sodium hyaluronate 3%, Alcon, Fort Worth, Texas]
to levitate the nucleus from a pars plana approach,” Dr. Chang
said. This technique allows the surgeon to approach the nucleus from
below. As a result, it can be pushed anteriorly rather than pulling it
forward with aspiration, Dr. Chang explained. If the surgeon succeeds in levitating the residual nucleus, cautiously
continuing phacoemulsification is an option if there is no vitreous prolapse
and if a trimmed sheet glide can be positioned behind the nucleus. “As
popularized by Marc Michelson, [M.D., Birmingham, Ala.] this artificial
posterior capsule can simultaneously prevent the pieces from falling
posteriorly and shield the aspirating tip from ensnaring vitreous,” Dr.
Chang said. “The alternative is to enlarge the incision in order
to manually extract the nucleus with a lens loop—a safer option
with a large or dense nucleus or if vitreous prolapse has already occurred.”
In 2003, Dr. Chang together with Dr. Packard published a combined series
of eight cases managed with the Viscoat PAL technique in the October
2003 issue of the Journal of Cataract and Refractive Surgery. They were
able to retrieve the partially descending nucleus in all eight consecutive
cases and were able to implant a posterior chamber IOL in seven eyes
following either phaco (50%) or manual ECCE (50%) removal of the nucleus.
They reported no posterior segment complications during the minimum 18-month
follow-up period.
Mastering the method Dr. Chang believes that a combination of the Kelman and Packard principles
works the best. “The first priority is to stabilize and support
the nucleus that is threatening to sink.” He finds that the pars
plana provides the ideal angle of approach to quickly inject a dispersive
OVD such as Viscoat or Healon D (sodium hyaluronate 3%, Advanced Medical
Optics, Santa Ana, Calif.) behind the nucleus to support it and prevent
further descent. “If necessary, subsequent injections of OVD can
hydraulically maneuver the pieces into a central position from which
they can be mechanically lifted with the OVD cannula tip,” Dr.
Chang said. “Additional OVD aliquots can be injected whenever the
need to reposition the pieces arises.”
Dr. Chang recommends using a dispersive OVD rather than a cohesive one
in this situation. “It tends to stay where it is injected, rendering
it most effective as an OVD safety net,” he said. “Secondly,
it better resists being aspirated or burped out, which is a desirable
property in these situations.” Finally, he notes that because much of the posteriorly injected OVD will
not be surgically removed, the smaller molecular weight dispersive OVD
is less likely to cause a severe IOP rise. In performing the PAL technique, Dr. Chang uses a disposable MVR blade
to make the pars plana sclerotomy 3.5 mm behind the limbus in the oblique
quadrant which best aligns with the surgeon’s dominant hand. “The
peritomy, the cautery, and the sclerotomy can be performed with the patient
still under topical anesthesia alone if necessary,” he said. “If
there is a more urgent time frame, placing a disposable 25-gauge needle
on the OVD syringe and directly injecting through the conjunctiva and
the pars plana can save valuable time.”
During the procedure it is important to keep the cannula tip in view
as much as possible . “This maneuver is not appropriate once the
nucleus has descended to the posterior half of the vitreous cavity,” Dr.
Chang said. He cautions that it is also important to avoid excessive
OVD injection because this can raise the intravitreal pressure to dangerous
levels and cause tissue expulsion through an incision.
Overall, Dr. Chang acknowledges that many cataract surgeons will not
be comfortable performing these techniques. “Many anterior surgeons
will understand, embrace and feel comfortable applying these principles
in appropriate cases,” he said. “However it is important
that individual cataract surgeons not overstep the boundaries of their
experience and skill set. Removing retained lens material from the posterior
segment can always be done in a second and appropriately timed procedure
by a vitreoretinal surgeon with an excellent prognosis.” Editors’ note:
Dr. Chang’s
consultant fees from Advanced Medical Optics (Santa Ana, Calif.)
and Alcon (Fort Worth, Texas) are donated to the Himalayan Cataract
Project. Contact information |
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