Thomas John
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Sutureless corneal transplantation surgery is sufficiently challenging in and of itself, so any improvement in the technique
that lowers the rate of reoperation because of a poorly positioned donor disc or disc detachment is worthy of discussion.
Instilling a drop of indocyanine green (ICG) (IC-Green, Akorn) or trypan blue 0.1% (Vision Blue, Dutch Ophthalmic Research
Co.), the latter of which is newly approved by the FDA, on the donor corneal stroma makes visualization and positioning of
the tissue markedly easier. This in turn facilitates proper centration, augments visualization of the host-donor interface,
and facilitates decreasing or elimination of any interface air bubbles, and thus, lowers the need for a second surgery to
adjust the position of the grafted tissue or reattachment of a detached disc.
Ernest W. Kornmehl, MD, editor of Anterior Segment Techniques, reviewed this column. He is medical director, Kornmehl Laser
Eye Associates, Boston, and is on the faculty of Harvard and Tufts medical schools and the Massachusetts Institute of Technology.
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When performing this transplantation surgery, the partial-thickness donor graft is placed in the host anterior chamber and
attached to the host cornea from the inside surface of the cornea. When the donor disc is placed in the anterior chamber of
the patient's eye, the disc must be properly oriented and attached in terms of centration and uniform attachment of the donor
disc to the recipient cornea. The host corneas in these cases are cloudy because of endothelial decompensation, resulting
in suboptimal visualization of the donor disc when it is placed in the host anterior chamber. Staining the donor disc stroma
with either ICG or trypan blue helps the surgeon properly orient the donor disc and minimizes the incidence of a second surgery.
This use of the two dyes grew out of their use to stain the lens capsule during cataract surgery.
There are two types of sutureless corneal transplantation surgery: deep lamellar endothelial keratoplasty (DLEK) and the newer
descemetorhexis with endokeratoplasty (DXEK). In the former, the deep stroma and the endothelium of the host cornea are removed
as a single disc; in the latter, only Descemet's membrane with the endothelium is removed. In DLEK, there is a coin-shaped
defect in the host cornea that is then plugged with the donor disc; since only Descemet's membrane is removed in DXEK, the
donor disc is attached to the host cornea much like a "pie on the ceiling."
Figure 1 The blue color from trypan blue 0.1% (Vision Blue, Dutch Ophthalmic Research Co.), recently approved by the FDA,
helps in centering the donor corneal stroma disc.
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The donor cornea is first placed in an artificial anterior chamber and the chamber then is pressurized. An automated microkeratome
(Moria Inc., Doylestown, PA) is used to remove the anterior portion of the donor cornea to a depth of 350 m. Removal of the
donor cap exposes the deep donor corneal stroma. At this point in the procedure, while the donor tissue is in the pressurized
chamber, either ICG or trypan blue can be applied to the stroma. The donor cap is returned into position and the entire donor
is removed as a unit from the artificial anterior chamber and placed epithelial side down into a donor punch (Moria).
A disposable trephine (Moria) with a diameter based on surgeon preference is used in a guillotine fashion to punch the donor
disc. The donor disc is then folded in a manner resembling a taco. The surface of the taco is either blue or green depending
on which dye was used.
Figure 2 Blue-stained disc is to the right.
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A small amount of a viscoelastic agent is placed inside the taco to protect the endothelium. The taco is then inserted inside
the patient's anterior chamber. The folded taco is better visualized through the cloudy cornea because of the stain.
Air is then used to unfold the taco inside the anterior chamber. If the donor disc is not properly centered after it is unfolded,
it can be moved easily into position onto the host inner corneal surface with a reverse Sinskey hook over an air bubble.
Figure 3 The descemetorhexis.
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Making this slight adjustment in the procedure has resulted in substantially better centration of the donor tissue and better
attachment of the donor disc to the host cornea compared with procedures done without staining the stroma.
A controlled study that evaluates patient outcomes with the use of stain versus without the use of dye should be undertaken
to quantitate the outcomes.
Figure 4 Scoring Descemet's membrane.
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After almost 4 years of follow-up using ICG during sutureless corneal transplantation, no adverse effects of using the dye
are evident. Trypan blue only recently became available and follow-up time is too short to make adefinitive statement regarding
any potential complications. None of the eyes with trypan blue-stained donor corneal disc has shown any complications thus
far. In this regard, the use of dye seems to be safer in corneal transplantation procedures, although there is only anecdotal
evidence to support this.
Use of dyes in corneal transplantation differs from that in cataract surgery. In the latter, the dye is injected into the
anterior chamber and the ocular tissues are directly exposed to the dye.
Figure 5 Final position of the disc with trypan blue 0.1% (Vision Blue, Dutch Ophthalmic Research Co.) and air. (Photos courtesy
of Thomas John, MD)
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In sutureless corneal transplantation, the dye stains the exposed donor corneal stroma and hence there is no free-floating
dye in the eye.
By the end of the transplantation procedure, about 40% of trypan blue has disappeared from the eye compared with about 5%
of ICG.
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Both ICG and trypan blue are equally effective in facilitating visualization of the donor disc.
Thomas John, MD, is clinical associate professor of ophthalmology, Loyola University at Chicago, and in private practice in Tinley Park and
Oak Lawn, IL, and Merrillville, IN. He is thought to be first to report the use of ICG during sutureless corneal transplantation
surgery. Dr. John has no proprietary interest in any aspect of this report. Readers may contact him via e-mail at cornea999@aol.com
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