by C. Douglas Witherspoon, MD
published in "VitreoRetinal Surgery & Technology-The Newsletter
of Vitreoretinal Surgeons,"Volume 1, Number 1, January/February
(TKP) vitrectomy is a useful approach to the treatment of patients
with severe posterior segment disease combined with corneal opacification.
Such patients include those with severe combined anterior and posterior
segment trauma; retinal detachment combined with pseudophakic bullous
keratopathy or graft failure; and fulminant bacterial endophthalmitis....
We believe TKP deserves greater consideration relative to
the alternatives of no surgery, consecutive penetrating keratoplasty
and vitrectomy, limited vitrectomy, endoscopy or eneucleation.
After ultrasound/VEP/ERG evaluation and thorough patient counseling,
initial surgical steps include conjunctival peritomy and isolation
of the rectus muscles on traction sutures if scleral buckling is
anticipated. A Flieringa ring to aid in TKP emplacement is optional.
A 6-mm infusion cannula is secured to the sclera, 3.5mm posterior
to the limbus and usually in the inferotemporal quadrant, avoiding
abnormal anterior structures. If choroidal detachment, scarring
or retinal detachment is suspected anteriorly, insertion of the
infusion cannula is delayed until after trephination of the cornea
to allow for direct viewing of the anterior structures prior to
emplacement. In any case, the infusion cannula is not turned
on until it can be ascertained that the tip of the cannula is in
the vitreous cavity and free of any obstructing material. We
prefer the use of gas-forced liquid infusion to allow for rapid
and accurate changes in intraocular pressure often necessitated
by this procedure.
The recipient corneal bed is best created with a vacuum trephine.
The trephine is usually centered on the cornea, even in the
presence of freshly closed lacerations which will be contacted.
An 8-mm recipient bed is used for the Lnaders-Foulks-Mannis
keratoprosthesis (8.2mm, hard plastic); a 7-mm bed is used for the
7.5-mm Eckhardt silicone-rubber prosthesis. The Eckhardt TKP is
said to be disposable, although it may be reused several times.
It is relatively more difficult to insert, but upon insertion
it provides an excellent view of the peripheral vitreous cavity.
Emplacement of all keratoprosthesis requires an aphakic eye and
is best achieved with stabilization of the TKP by an assistant;
for example, slight downward pressure with a cotton-tipped applicator
as the Landers prosthesis is rotated....
Most injuries requiring TKP vitrectomy involve considerable disorganization
of the anterior segment in the form of iris loss, hyphema, lens
laceration and ciliary body laceration. Not infrequently,
the retina is highly detached and approaching the anterior segment.
After trephination of the cornea, meticulous open-sky reconstruction
of the anterior segment, including viewing of the infusion cannula,
is advisable prior to TKP emplacement.
Once the TKP is secured to the cornea, closed posterior vitrectomy
can take place as usual. The four-strut Landers TKP requires
no supplemental contact lens, but scleral depression is necessary
to completely view the retinal periphery. The Eckhardt TKP
requires a supplemental contact lens. Air-fluid exchange causes
the Landers prosthesis to fog with water vapor; however, a small
amount of viscoelastic material placed on the internal surface of
the prosthesis will provide an adequate view. Following vitrectomy,
scleral buckling may be performed in the usual fashion, preferably
prior to corneal transplantation.
Using optimal donor tissue, we have achieved late graft clarity
in over 80% of stable eyes, which is comparable to elective transplantation.
Silicone oil keratopathy has not been a significant
problem when the use of silicone oil has been essential for retinal
With proper attention to details, severely damaged eyes may be
salvaged with TKP techniques. Many of these eyes would otherwise
be lost because of delayed or inadequate surgery. The decision
for attempted reconstruction or for enucleation can then be made
in a timely manner, in keeping with the surgeon's experienced judgment
and the patient's perceived wishes....
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us at 205-933-2625 or 800-292-8166
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