Transcript 859: Irish Experience with a PMMA Keratoprosthesis

Boston Keratoprosthesis – the Eye and Ear Experience
J Brady, W Power
The Authors have no financial interest in the subject matter of this poster
Royal Victoria Eye and Ear Hospital, Dublin
Background
Keratoprosthesis devices were initially developed to overcome the problem of multiple failed grafts. Although first time corneal grafts have a success rate of >95% over ten years, this diminishes with each successive graft.
Bersudsky et al. determined that survival rates for first time repeat grafts were 55% at 3.5 years, and 28% at 4.5 years (1). Second time regrafts had survival rates of 45% at 3.5 years and 20% at 4.5 years(2). Subgroups
of patients are a higher risk of graft failure such as those with a history of glaucoma, ocular surface disease or inflammation, stem cell defiency or multiple ocular surgeries.
The Boston Keratoprosthesis (Kpro) first received FDA approval in 1992 and there have been more then 3000 implantations to date. It has the advantage that only one procedure is required unlike other prostheses such
as AlphaCor or Osteo-Odonto-Keratoprosthesis. The Multicenter Boston Type 1 Keratoprosthesis Study (MBTKS), a prospective case series of 141 cases from 17 centres with an average follow up of 8.5 months, report
retention rates of 95% with visual acuity outcomes of greater than 20/40 in 23% of patients and greater than 20/200 in 57% of patients. Failure for visual acuity to improve from the Boston Keratoprosthesis was attributed
to underlying ocular disease such as advanced glaucoma, macular degeneration, or retinal detachment (3). Success rates depend on the preoperative diagnosis. According to Yaghouti et al the percentage of patients
obtaining a VA of 6/60 or greater was 33% at years in Stevens Johnson Syndrome compared with 64%over the same time scale in alkali burns, 72% in Ocular Cicatricial Pemphigoid and 83% in graft failure patients
Structure (5)
A Type I KPro consists of two PMMA plates which clamp a corneal graft. The back plate has 16 holes to communicate with aqueous
providing nutrition and hydration to the cornea (6). The assembly is locked with a titanium ring. It has an antero-posterior length of
approximately 3.7mm with a field of vision of 60 degrees.
A Type II KPro is used for patients with severe ocular surface disease who have no fornices to support the graft. has a 2 mm long
anterior nub off the front plate which penetrates skin or buccal mucosa.
Indications
•2 Failed Grafts with poor prognosis for further grafting
•VA < 20/200 in the affected eye
•No end stage glaucoma or retinal detachment
Assessment
•VA < 20/200 with reduced vision also in the other eye
•Intact light projection
•Intact lid/blink mechanism to retain a BCL
•Ocular Surface disease
•Slit Lamp exam including tonometry
•Comorbidities must be assessed such as Retinal detachment/end stage glaucoma (obvious contraindications)
•If iop control is suboptimal consider a shunt procedure pre Kpro implantation
•A scan to select the refractive power of the Kpro
1M
Diagnosis
69
L
Interstitial keratitis
Lens opacity
2F
3M
84
68
L
L
Salzmamn Keratopathy
Lime injury
stem cell failure
Blind in other eye from old perforation
CF
HM
4M
70
L
Explosion Right eye enucleated
Left corneal decompensation
2 failed grafts
HM
5F
79
Type II
R
Ocular cicatricial pemphigoid
L NPL
6M
63
R
7M
57
L
8F
Postoperative Followup
•Bandage Contact lens worn at all times: the irregular shape and material of the prosthesis induces evaporative
forces on the cornea. There is an increased risk of epithelial defects, stromal thinning, and dellen formation.
The BCL is very protective of corneal tissue hydration and reduces the chance of these complications (8).
•Lifelong prophylactic antibiotic drops (see below – in our unit we use Ofloxacin drops and in some high risk patients
rotate between vancomycin, chloromycetin and oflocacin every six weeks (9,10).
RVEEH Results
We present a series of 13 patients who have undergone Boston Keratoprosthesis insertion in our unit over the last five years. Mean follow-up was
32.3 months (range 11 - 60). The compares with an average follow-up of 8.5 months in the MBKTS trial.
Preoperative Diagnosis: 3 patients underwent Type II Kpros with cicatrizing conditions. 2 had Ocular Cicatricial Pemphigoid and one had Stevens
Johnson Syndrome. Three had a diagnosis of a previous alkali burn and one patient had a previous thermal injury. Three patients underwent the
procedure post graft failure and 4 had a preoperative diagnosis of interstitial keratitis.
Preoperative Visual Acuity: ranged from PL to 6/60. Of the group, 8/13 were CF or worse. 7/13 procedures were carried out in only eyes.
Preoperative Co-morbidity: 2/13 had coexistent glaucoma. This is lower than the quoted rate of 60% in MBKTS.
Postoperative Visual Acuity: ranged from NPL to 6/9. Of the twelve patients with recordable postoperative vision (excluding one patient with a
recently implanted Type II Kpro who has yet to have the tarsarraphy opened) nine have a visual acuity of 6/60 or better. 7/12 have visual acuity of
6/12 or better.Ten of the twelve registered a visual improvement. Two patients who did not register an improvement developed postoperative
glaucoma with subsequent optic nerve damage. MKBTS reported postoperative vision of 6/60 or greater in 57%
Postoperative Complications:There were two cases of postoperative endophthalmitis which occurred at two months in both patients. However at
last follow-up these patients had post treatment vision of 6/12 and 6/9 respectively. One patient developed a retroprosthetic membrane but
unfortunately passed away before treatment. Postoperative trauma with globe rupture limited the visual potential of another patient. Finally four
patients developed postoperative glaucoma which was controlled in three cases but unfortunately one patient did not respond to treatment and
became NPL. Graft retention was 100%.
Discussion
The Boston type 1 keratoprosthesis is a viable option after multiple keratoplasty failures or in conditions with a poor prognosis for primary keratoplasty.
Patients with autoimmune disease are at higher risk for complications. With regard to the main outcome measures of retention and visual acuity our
results compare well with those published in the largest study to date – the MBKTS trial.
Age at
81
Eye
Diagnosis
Preop
Comorbidities
BCVA
6/60
Postop
Complications
Follow-up
BCVA
6/9
nil
(months)
40
6/12
CF
nil
Postoperative trauma
Ruptured graft with iris prolapse
39
38
HM
Developed end stage glaucoma
23
6/60
6/12
Endophthalmitis at 2 months
26
Alkali burn 1999 L NPL
Previous failed R stem cell transplant
HM
6/12
Postoperative glaucoma
Controlled with topical therapy
22
R NPL
Left retinal detachment repair with
oil – corneal decompensation
HM
NPL
6 months post surgery admitted with
eye pain high IOP. Despite treatment
developed pale disc
50
Disc Pallor
Left amblyopia
Left glaucoma
x 27 years
R
Interstitial Keratitis
6/60
6/12
9M
80
L
Interstitial Keratitis
CF
6/30
Retroprosthetic membrane but RIP
before treatment
46
23
10 M
36
R
Alkali burns – stem cell failure
Failed stem cell transplant RE
6/120
6/9
High intraocular pressure one month post
surgery – Ahmed Valve- now controlled
25
11 F
80
Type II
L
Ocular cicatricial pemphigoid
Previous perforation and tectonic
graft R NPL
PL
6/60
Revision of Kpro plus scleral patch at 7 months
60
12 F
44
Type II
R
Stevens Johnson syndrome
L NPL
PL
13 M
62
L
Interstitial Keratitis
CF
Fig 1 Structure of Keratoprosthesis
Surgery
•Approx 90 minutes
Kpro is inserted into a corneal graft. The natural lens is removed but to avoid vitreous prolapse pseudophakes
retain their lens.
Complications
•Early problems of melt and extrusion have been virtually eliminated
•Retroprosthetic membrane: This occurred in 25% of the MBTKS cohort. Most do not require treatment and if it is necessary YAG laser is sufficient
to remove nonvascularised membranes. In the rare instances of vascularised membranes, VR intervention is required (11).
•Retinal Detachment: with a reported incidence in MBKTS of 3% 3,11)
•Endophthalmitis: Before the routine use of daily vancomycin drops, high incidences of bacterial endophthalmitis from gram positive cocci were
reported (10). It is fortunately very rare in the graft failure group as long as prophylactic antibiotics are used. Dohlman et al recommend prophylactic
vancomycin in high risk patients (Stevens Johnson Syndrome, Ocular Cicatricial Pemphigoid, only eyes). Khan et al. reports no cases of bacterial
endophthalmitis over a period of six years when utilizing prophylactic Vancomycin drops (9).
•Vitritis sudden painless sharp decrease in vision.It there is no pain or redness patients can be treated with peribulbar triamcinolone and
prophylactic antibiotics – they always clear up (12).
•Can worsen glaucoma. In the MBKTS 53% had glaucoma pre Kpro insertion. Unfortunately post Kpro insertion accurate tonometry is no longer
possible and assessment of glaucoma progression is carried out by monitoring discs and visual fields (3,13).
Patient
6/9
Tarsorraphy not opened yet
11
Postoperative endophthalmitis
17
Fig 2 Type I Keratoprosthesis in situ
References:
Fig 3 Retroprosthetic membrane
1.
Bersudsky V, Blum-Haeuveni T, Rehany U et al. The profile of repeated corneal transplantaion. Ophthalmology 2001;108:461-469
2.
Williams KA, Ash JK, Pararajasegaram P, et al. Long-term outcome after corneal transplantation. Visual result and patient perception of success. Ophthalmology.
1991;98:651-657
3.
Zerbe BL, Belin MW, Ciolino JB; Boston Type 1 Keratoprosthesis Study Group.1: Results from the multicenter Boston Type 1 Keratoprosthesis Study. Ophthalmology.2006
Oct;113(10):1779.e1-7.
4.
Yaghouti F, Nouri M, Abad JC, Power WJ, Doane MG, Dohlman CH.Keratoprosthesis: preoperative prognostic categories. Cornea. 2001Jan;20(1):19-23.
5.
Doane MG, Dohlman CH, Bearse G. Fabrication of a keratoprosthesis. Cornea.1996 Mar;15(2):179-84.
6.
Harissi-Dagher M, Khan BF, Schaumberg DA, Dohlman CH. Importance of nutrition to corneal grafts when used as a carrier of the Boston Keratoprosthesis. Cornea. 2007
Jun;26(5):564-8.
7.
Khan B, Dudenhoefer EJ, Dohlman CH. Keratoprosthesis: an update. Curr Opin Ophthalmol. 2001 Aug;12(4):282-7. Review.
8.
Dohlman CH, Dudenhoefer EJ, Khan BF, Morneault S. Protection of the ocular surface after keratoprosthesis surgery: the role of soft contact lenses. CLAO J. 2002
Apr;28(2):72-4.
9.
Khan BF, Harissi-Dagher M, Khan DM, Dohlman CH. Advances in Boston keratoprosthesis: enhancing retention and prevention of infection and inflammation. Int
Ophthalmol Clin. 2007 Spring;47(2):61-71
10.
Nouri M, Terada H, Alfonso EC, Foster CS, Durand ML, Dohlman CH.Endophthalmitis after keratoprosthesis: incidence, bacterial causes, and risk factors. Arch
Ophthalmol. 2001 Apr;119(4):484-9.
11.
Ray S, Khan BF, Dohlman CH, D'Amico DJ. Management of vitreoretinal complications in eyes with permanent keratoprosthesis. Arch Ophthalmol. 2002 May;120(5):55966.
12.
Nouri M, Durand ML, Dohlman CH. Sudden reversible vitritis after keratoprosthesis: an immune phenomenon?. Cornea. 2005 Nov;24(8):915-9.
13.
Birkholz ES, Goins KM. Boston Keratoprosthesis: An option for patients with multiple failed corneal grafts. March 9, 2009. Available from:
http://webeye.ophth.uiowa.edu/eyeforum/cases/94-Boston-Keratoprosthesis-Failed-Corneal-Graft.htm.