Dr. Gulani
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Jacksonville, FL-The chances of pterygium
recurrence can be decreased substantially by removing the entire
pterygium, not simply the head. In cases of extensive excision,
amniotic membrane transplantation seems to provide excellent
results, according to Arun Gulani, MD.
"The part of the pterygium that
is visible is only the tip of the iceberg," said Dr. Gulani, chief
of cornea external disease and director, refractive sur-gery,
University of Florida, Jacksonville. "Removing only this visible
portion may confuse our understanding of extension of the same
pterygium as opposed to true recurrence and lead to baffling
recurrence rates.
"By removing only this visible
portion, the main pathology with its tentacles is not addressed and
remains hidden under the conjunctiva," he said. "Pterygium is one of
the oldest ocular pathologies known and its cause and effective
management are still being debated."
Theories about the etiology of
pterygia are diverse and range from hereditary, neurotrophic,
angioplastic, and immunologic causes to ultraviolet light exposure.
Regardless of the cause, the result is elastotic degeneration with
vesiculation of Bowman's membrane in the cornea and the formation of
epithelial islets (Fuchs' patches) as cysts around the pterygium
(seen as glovefinger appearance on histopathologic study), according
to Dr. Gulani.
He said that the expression of
vimentin (indicator of migration) by the keratoblasts and increased
P53 (protein accumulation due to defective tumor suppression gene)
make one think of the concept of a migrating limbus.
Anatomically, the pterygium is
composed of several segments, including Fuchs' patches and Stocker's
line (the iron line), the hood, the head, the body, and the superior
and inferior edges.
Pterygia can be classified into
three types, Dr. Gulani explained.
Figure 1 A pterygium may have to be
excised if it infringes on vision either directly or by
causing astigmatism or tear film abnormalities.
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Type 1
is the classic peripheral formation, type 2 involves the optic zone
and can infringe on vision directly or indirectly by causing
astigmatism or tear film abnormalities, and type 3 has tentacles and
scar-ring that produce oculomotor symptoms and fibrosis.
Dr. Gulani also suggested an
addition to this classification of a type 4 that is recurrent and
aggressively malignant.
Amniotic membranes, which are
composed of a monostratified epithelial (nonsticky) surface, a
basement membrane, and a stromal (sticky) side, have been used in
medicine for about 60 years. The advantages of the commercially
available membrane are that there is no immune reaction and it has
anti-inflammatory functions, is anti-adhesive and anti-bacterial,
encourages epithelial differentiation and growth, and has an
anti-tissue growth factor effect, Dr. Gulani explained.
"The basement membrane is a type
4 collagen with laminin," he said. "The beauty of this structure is
that it is similar to the basement membrane of the conjunctiva. The
epithelium has growth factors that encourage growth and
differentiation into conjunctiva and corneal epithelium. We apply
the membrane in a double-folded form, so that there is smooth
epithelium on both sides, superiorly for epithelialization and below
for smooth movement of the underlying extraocular muscle."
He uses three different criteria
to determine surgical intervention:
- The extent of the pterygium.
- Density of the pterygium.
- Involvement of adjacent structures.
Further, each of the four types
can be stationary or active; the knowledge of this also guides
treatment.
Because of the complex structure
of the pterygium, dissecting only the head is ineffective. The
underlying structures are the ones that actually grow and move the
head into the cornea, Dr. Gulani pointed out.
Figure 2 The postoperative amniotic
membrane graft following advanced pterygium excision.
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Thus
far, most treatments, such as copper sulfate, silver nitrate,
mitomycin-C, thiotepa, and 5-fluorouracil, have been ineffective and
associated with major side effects. Argon laser treatment has been
used to contract conjunctival tissue and treat blood vessels.
Radiation with strontium 90 has been used postoperatively, but
patients must be followed for years because of the potential side
effects such as scleral/corneal melting.
Indications for surgery include
correction of cosmetic defects; visual effects such as location
within the visual axis and induction of astigmatism or dry eye; and
recurrence of the pterygium in which patients present with scars and
extremely aggressive pterygia. Atrophic pterygia do not require
surgery.
After measuring corneal
pachymetry and refraction, Dr. Gulani also uses a special slit-lamp
video system along with the Orbscan to determine three-dimensional
involvement of the cornea along with the astigmatic component. This
also helps to educate the patients visually. The surgeon can
determine both if the pterygium is progressive and how far it has
pulled in the medial fold in the conjunctiva.
Also, the extraocular motility
will help determine whether the pterygium is in stage 3 or 4.
Iceberg concept
At the start of the procedure, the
head of the pterygium is lifted off the cornea. After smoothing the
cornea, topical epinephrine is used to create vascular hemostasis.
"The most important stage is
dissecting the pterygium," Dr. Gulani said. "The whole plane of the
pterygium is delineated subconjunctivally. When it is removed, it
resembles a spreading mass of tentacles. It is important to remove
the entire mass to avoid recurrence."
The pterygium is dissected
carefully superiorly, to avoid buttonholing the conjunctiva and
invading the orbital septum, and inferiorly, to avoid cutting the
underlying muscles, which is rechecked after the pterygium is
removed. He uses sharp dissection superiorly and resistive
separation inferior to the pterygium.
Figure 3 Iceberg concept: The pterygium
visibly removed (smaller piece) during pterygium surgery and
the real amount of pterygium that actually needs to be
removed. This picture shows the discrepancy in what actually
should be entirely dissected and removed as visualized on the
scale.
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He has designed the Gulani-Tseng
instrument set for this surgery.
Weck cell sponge pieces are
soaked in mitomycin-C 0.04% and placed under the conjunctiva (rolled
over these pieces) in the area of the dissection and left in place
for 1 to 2 minutes to prevent fibrosis as well as recurrence from
the subconjunctival tissue. After removing the sponges, the area is
flushed with balanced salt solution.
Dr. Gulani uses the cornea as an
illuminated receiving table to drape the amniotic membrane as he
receives it with a two-handed technique from the nitrocellulose
paper before folding it in a controlled fashion. At the same time,
with the retroillumination through the cornea (pupil is dilated by
now due to topical use of epinephrine for hemostasis) he can, in
cases of dehydrated amniotic membrane (such as Ambiodry), use this
to confirm readiness of application by looking for the disappearance
of what he calls "the waffle board sign."
"After folding the amniotic
membrane over a specially designed instrument, both the stromal
sides come together and the epithelial sides are facing up and
down," he said. "The central closed portion with the edges
positioned medially is then aligned to the limbus."
Dr. Gulani said he may fashion
slits at this juncture to milk any active folds for uniformed
draping.
Figure 4 Aggressive recurrent pterygium
referred for re-operation. Stage 4 with muscle
involvement.
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Excessive membrane is then removed.
Suturing with 10-0 nylon is started after the membrane has been
smoothed. Using a nonholding technique, both layers of the amniotic
membrane are engaged and the needle is pushed through the sclera and
episclera in a long central bite close to the limbus. Dr. Gulani has
designed a new needle to facilitate this step. When this is anchored
well, the process is completed along the limbus and the stitches are
buried in the sclera, according to Dr. Gulani.
The next step is spreading the
edges of the membrane under the conjunctiva. The bite goes through
the conjunctiva, both amniotic membrane layers, episclera and
superficial sclera, and then out in the same order; this is anchored
with 8-0 Vicryl. On the medial side, the membrane is stitched to the
conjunctiva and temporally to the limbus. After smoothing the
membrane and rechecking hemostasis, the procedure is finished.
He emphasized the importance of
long follow-up periods, minimally 2 years. He pointed out that in
addition to detecting a recurrence, one should also watch out for
any long-term complications.
Dr. Gulani has taught his
technique internationally and trains surgeons in this advanced level
of care.
Figure 5 Postoperative results with
freely mobile, clear eye with 20/20 uncorrected vision.
(Photos courtesy of Arun Gulani, MD)
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"The
procedure of amniotic membrane transplantation has a wide spectrum
of applications in ocular surface correction," Dr. Gulani said. "It
acts like a natural contact lens; it replaces tissue, acts as a
scaffold for tissue to grow, and is protective physically and
chemically. Amniotic membrane could literally be woven into a
contact lens or grown into a contact lens that could be used for an
emergent situation."
Bibliography
Gulani AC. Simultaneous
pterygiumand cataract surgery. J Postgrad Med 1995;41:8-11.
Gulani AC. "Dry Eye Matrix."
Innovator's Lecture, ASCRS, 2002.
