corneal transplantation is generally successful for reversing corneal blindness.
There are, however, some patients who are not amenable to such transplantation.
They typically have severely dry eyes and the only procedure that may work
is keratoprosthesis. Strampelli described the original technique of osteo-odonto-keratoprosthesis
(OOKP) surgery nearly forty years ago, using the patient's own tooth root
and alveolar bone as vital support to an optical cylinder 1.
Early British followers of his technique reported poor retention results
Falcinelli modified the technique in a stepwise fashion 3-6
and the improved technique was re-introduced into Britain, at our hospital,
1996 7. The Falcinelli OOKP, where adequately performed, is
now recognised internationally to give the best long term visual and retention
results amongst all keratoprosthesis, especially in a dry eye.
with bilateral corneal blindness resulting from severe Stevens-Johnson
syndrome, ocular cicatricial pemphigoid, chemical burns, trachoma, dry
eyes or multiple corneal graft failure may be considered. The better, or
only, eye should have poor vision such as PL, HM or at best CF. One eye
only will be rehabilitated. In suitable cases, there would be no need to
go through unsuccessful penetrating keratoplasty with or without limbal
stem cells transplantation and amniotic membrane grafting beforehand. Previous
history of retinal disesase, glaucoma and other optic nerve disease, ocular
perforation, as well as pre-phthisis may compromise outcome.
OOKP assessment clinic
joint clinic is run by an ophthalmologist (CL) and a maxillo-facial surgeon
(JH). Pre-operative assessment includes ascertaining an intact and functioning
retina and optic nerve by relatively accurate projection of light in quadrants,
a normal B-scan (also for axial length), and in selected cases flash ERG
and VEP. Following oral examination and radiography, a choice is made as
to which tooth (usually a canine) to harvest depending on the length and
girth of the root, the state of surrounding alveolar bone, and the amount
of gum recession. In the absence of a suitable single-rooted tooth, the
use of an HLA-matched relative's tooth is possible, but prolonged immunosuppression
with cyclosporine will be necessary. The patient and their relatives are
counselled regarding the complexity of surgery, success rates, possible
complications and their management (see Table 1) and that they should consider
the procedure as irreversible. A new optical cylinder we developed is shorter
and wider than the original Italian design providing a much wider but still
restricted field of view (circa 100 degree), which has been found to be
beneficial in patients with age related macular degeration 8.
surgery is performed usually in two stages spaced two to four months apart.
The gap allows soft tissue to grow around the osteo-odonto lamina and for
ocular surface reconstruction with buccal mucous membrane grafting to become
1: Potential complications of OOKP surgery
mucous ulceration in the early post operative period (especially in smokers)
malposition and loss of fornix
of optical cylinder
to adjacent tooth
of cyclosporine treatment
stage takes approximately six hours and special anaesthetic precautions
are necessary 9. Prior to OOKP surgery, it is important to treat
pre-existing glaucoma by cyclodestruction. Fornix reconstruction, where
necessary, can be carried out beforehand or at the time of stage 1 procedure.
1 involves ocular surface reconstruction and fashioning of an osteo-odonto
lamina and its optical cylinder. A large circular piece of buccal mucosa
is harvested from the cheek. The graft is trimmed of excess fat and soaked
in cefuroxime solution. A lateral canthotomy is performed, followed by
division of symblephara and superficial keratectomy. The buccal mucous
membrane graft is sutured to the sclera bounded by the insertion of the
rectus muscles to create a new ocular surface. The crown of the harvested
tooth is used as a handle; whilst the attached tooth root and surrounding
bone is worked into a lamina with dentine on one side and bone on the other.
Periosteum is conserved and where possible glued back with fibrinogen adhesive.
A hole is drilled through the dentine to accommodate a PMMA optical cylinder,
which is cemented in place. The resultant osteo-odonto lamina is placed
into a sub-muscular pocket under orbicularis oculi, usually in the lower
lid of the fellow eye, in order to acquire a soft tissue covering.
2 starts with retrieval of the osteo-odonto lamina from its sub-muscular
pocket and excess soft tissue is removed from the bone surface. On the
dentine surface, no soft tissue is allowed to remain. The lamina is reinserted
into its pocket until the eye is ready to receive it. The buccal mucosal
graft is reflected to allow access to the cornea. A Flieringa ring is sutured
in place. The centre of the cornea is marked, and a small hole is trephined,
the diameter of which corresponds to that of posterior part of the optical
cylinder. Relieving incisions are made and total iridodialysis, lens extraction
and anterior vitrectomy are performed. The posterior part of the lamina
is inserted through the central corneal hole and the lamina is sutured
onto the cornea and sclera. The eye is re-inflated with filtered air. The
mucosal flap is replaced after cutting a hole to allow the protrusion of
the anterior part of the optical cylinder (Figures 1 and 2) 10.
reported excellent long term retention results (85% in 18 years) with 75%
of patients seeing 6/12 or better 10. In our unit, 9 out of
15 cases (60%) have a post operative vision of greater or equal to 6/24
and in 7 out of 15 cases (46.66%) post operative vision was greater or
equal to 6/12. Eighty percent of patients achieved improvement of vision.
In general, patients with compromised visual outcome have had pre-existing
optic nerve and retinal comorbidity.
surgery is complex and requires meticulous care at each step to ensure
the overall success rate. Therefore, surgeons must not attempt to provide
a service without first having undergone adequate training. Oral structures
have to be sacrificed. All patients experience glare and a restricted visual
field. The cost of OOKP surgery to the NHS is in the region of eight to
ten thousand pounds and formal cost benefit analysis has confirmed its
cost effectiveness (unpublished data). Although it is far from perfect,
modern OOKP surgery is the only hope for restoring sight in the long term
for desperate cases of corneal blindness not amenable to conventional corneal
Liu, Padmanabha Pillai Syam, Jim Herold and Simon Thorp, Sussex Eye Hospital,
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