Download The Boston Keratoprosthesis Type II: The Massachusetts Eye and

CLINICAL SCIENCE
The Boston Keratoprosthesis Type II: The Massachusetts
Eye and Ear Infirmary Experience
Siddharth Pujari, MS(Oph), MPH, Sana S. Siddique, MD, Claes H. Dohlman, MD, PhD,
and James Chodosh, MD, MPH
Purpose: To report the long-term outcomes of Boston keratoprosthesis type II implantation in the management of severe ocular surface
disease and corneal blindness through a retrospective interventional
case series.
Methods: This retrospective review included medical records of
patients who underwent Boston keratoprosthesis type II implantation at
the Massachusetts Eye and Ear Infirmary from January 1, 2000 through
December 31, 2009. The main outcome measures analyzed were visual
acuity, keratoprosthesis retention, and postoperative complications.
Results: A total of 29 eyes of 26 patients received a Boston
keratoprosthesis type II during the study period. Patients undergoing
operation had corneal blindness because of mucous membrane
pemphigoid (51.7%), Stevens–Johnson syndrome/toxic epidermal
necrolysis (41.4%), or other ocular surface disease (6.9%). Visual
acuity after surgery improved to 20/200 or better in 23 eyes (79.3%)
and to 20/30 or better in 10 eyes (34.5%). In patients with at least 1
year of follow-up (n = 21), visual acuity of 20/200 or better was
maintained in 12 eyes (57.1%). Of 13 eyes followed-up for more than
5 years, 6 eyes (46.2%) had visual acuity of 20/200 or better at the last
follow-up examination. Eyes that did not improve to 20/200 or lost
vision during the follow-up had end-stage glaucoma, previous retinal
detachment, or age-related macular degeneration. Of the total of 29
eyes, 17 devices (58.6%) were retained without extrusion or
replacement during a total follow-up time of 107.9 person-years.
Conclusions: The Boston keratoprosthesis type II is a viable option
for corneal blindness from severe autoimmune ocular surface
diseases.
Key Words: Boston keratoprosthesis, mucous membrane pemphigoid, Stevens–Johnson syndrome, long-term outcomes
(Cornea 2011;30:1298–1303)
Received for publication December 11, 2010; revision received January 16,
2011; accepted February 5, 2011.
From the Department of Ophthalmology, Massachusetts Eye and Ear
Infirmary, Harvard Medical School, Boston, MA.
Supported in part by an unrestricted grant to the Department of
Ophthalmology, Harvard Medical School from the Research to Prevent
Blindness, New York, NY.
The authors state that they have no proprietary interest in the products named
in this article.
Reprints: James Chodosh, Massachusetts Eye and Ear Infirmary, 243 Charles St,
Boston, MA, 02114 (e-mail: [email protected]).
Copyright Ó 2011 by Lippincott Williams & Wilkins
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K
eratoprosthesis implantation is primarily reserved for
patients with corneal blindness in whom standard corneal
allograft surgery has a poor prognosis.1 The development of
a keratoprosthesis was first proposed in 1789.2 The Boston
keratoprosthesis, a collar button–shaped device composed of
polymethylmethacrylate, was approved for marketing by the
Food and Drug Administration in 1992 and is now the most
commonly used keratoprosthesis in the world.3 The Boston
keratoprosthesis type I is used in patients with repeated corneal
allograft failure, corneal opacity with extensive neovascularization, and other indications in which conventional allograft
surgery would likely fail, such as aniridia. In contrast, patients
with severe autoimmune ocular surface diseases, such as
Stevens–Johnson syndrome/toxic epidermal necrolysis (SJS/
TEN), mucous membrane pemphigoid (MMP), and end-stage
keratoconjunctivitis sicca, and those after severe chemical
burns require a modified device, the so-called type II
keratoprosthesis, which is designed with an anterior extension
to allow implantation through surgically closed eyelids. On
practical grounds, the Boston keratoprosthesis type II (Fig. 1)
is generally reserved for patients with significant symblepharon or ankyloblepharon, ocular surface keratinization, and
absence of normal lid function. Several studies in the literature
report outcomes for the Boston keratoprosthesis type I,3–5 but,
to our knowledge, no similar report exists regarding the less
commonly implanted Boston keratoprosthesis type II. Here,
we report outcomes of type II keratoprosthesis surgery
performed at the Massachusetts Eye and Ear Infirmary over
the past decade.
MATERIAL AND METHODS
Patient Selection
The Human Studies Committee of the Massachusetts
Eye and Ear Infirmary approved this study. The project did not
fall under the Health Insurance Portability and Accountability
Act requirements because no protected health information was
recorded or linked by code to data.
We retrospectively reviewed the records of all patients
who underwent implantation of the Boston keratoprosthesis
type II at the Massachusetts Eye and Ear Infirmary from
January 1, 2000 through December 31, 2009 (n = 26). The
year 2000 was chosen as the start of our study because in 1999,
the device was modified to include holes in the keratoprosthesis back plate6,7 and topical vancomycin was added to
the postoperative regimen. These changes dramatically
reduced the incidence of corneal melting7 and Gram-positive
Cornea Volume 30, Number 12, December 2011
Cornea Volume 30, Number 12, December 2011
Boston Keratoprosthesis Type II Implantation
FIGURE 1. Before (L) and after (R)
photographs of a patient with
SJS who received implantation of
a Boston keratoprosthesis type II.
endophthalmitis,8 respectively. Additionally, a previous study
focused on SJS patients who received Boston keratoprosthesis
implantation and showed a marked improvement in outcomes
after 2000.9 We included only eyes in the study that had never
previously had a type II keratoprosthesis.
Surgical Technique
The details of Boston keratoprosthesis type I implantation have been previously described.10 Implantation of the
type II keratoprosthesis requires several additional steps. All
ocular surface mucosa is removed, including tarsal and
forniceal conjunctiva, before implantation of the device. Once
the keratoprosthesis is in place, a notch is fashioned in the
upper eyelid to accommodate the anterior extension of the
keratoprosthesis and a complete tarsorrhaphy is performed,
leaving only the anterior-most part of the keratoprosthesis
exposed (Fig. 1). Topical fluoroquinolone and vancomycin
drops are routinely used in patients after type II keratoprosthesis implantation to reduce bacterial colonization of the
perioptic skin and to prevent infection.
prekeratoprothesis and postkeratoprosthesis surgical procedures, and postoperative complications and outcomes were
recorded.
Main Outcome Measures
The main outcome measures were postoperative visual
acuity, device retention, and time to complications.
Statistical Analyses
All analyses were performed using commercial statistical software (Stata version 9.1; Stata Corp, College Station,
TX). Cumulative functional success, defined as the ratio of the
cumulative years with visual acuity of 20/200 or better to total
duration of time since implantation, was calculated. The
Kaplan–Meier method was used to study maintenance of
visual acuity of 20/200 or better if achieved after surgery and
retention of the device. Multiple logistic regression was used
to analyze continuous and categorical covariates potentially
affecting retention.
RESULTS
Data Collection
Data were collected by 2 physicians with experience in
ophthalmology, by retrospective chart review, and were
recorded in a Microsoft Access database (Microsoft, Redmond, WA). Nonidentifying patient demographics,
Baseline Characteristics
A total of 26 patients (29 eyes) underwent type II Boston
keratoprosthesis implantation. The demographics and clinical
characteristics are summarized in Table 1. The mean age at
TABLE 1. Pre–Boston Keratoprosthesis Type II Conditions
MMP
No. patients (eyes)
Female, n (%)
Mean age (SD), yr
Duration of inflammation (SD), yr
Systemic immunosuppression, n (%)
Prednisone
Antimetabolities
Alkylating agents
Intravenous immune globulin
Total on immunosuppression
Eye-specific characteristics, n (%)
Visual acuity 20/200 or worse
Advanced glaucoma
Previous glaucoma surgery
Previous retinal detachment repair
Previous Boston keratoprosthesis type 1
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SJS/TEN
13
6
70.2
16.6
(15)
(46.2)
(12.7)
(20.3)
11
8
50.5
11.4
(12)
(72.7)
(18.2)
(9.8)
3
1
2
1
7
(11.5)
(3.9)
(7.7)
(3.9)
(6.9)
1
1
1
0
3
(3.9)
(3.9)
(3.9)
(0)
(11.5)
14
8
10
1
4
(48.3)
(27.6)
(34.5)
(3.5)
(13.8)
12
1
2
0
1
(41.4)
(3.5)
(6.9)
(0)
(3.5)
Other
2
1
58.6
3.0
(2)
(50.0)
(29.9)
(0.9)
Total
26
15
61
13
(29)
(57.7)
(18.4)
(15.3)
—
—
—
0 (0)
0 (0)
4
2
3
1
10
(15.4)
(7.7)
(11.5)
(3.9)
(38.5)
2
1
1
0
0
28
10
13
1
5
(96.6)
(34.6)
(44.8)
(3.5)
(17.3)
(6.9)
(3.5)
(3.5)
(0)
(0)
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Cornea Volume 30, Number 12, December 2011
Pujari et al
implantation was 61 years (SD, 18.4 years). Patient gender was
approximately equally distributed (women, 57.7%). MMP
was the most common diagnosis (15 eyes; 51.7%), followed by
SJS/TEN (12 eyes; 41.4%) and other ocular surface
disease (6.9%), with the latter including 1 patient with
a chemical burn and 1 patient with severe radiation keratopathy
after treatment for lymphoma. The patients with MMP were
older than the patients with SJS/TEN. Seven patients (26.9%)
with MMP and 3 patients (11.5%) with SJS/TEN were using
immunosuppressive therapy at the time of implantation.
Nearly all eyes (96.6%) had a visual acuity 20/200 or worse
before Boston keratoprosthesis type II implantation (Table 1).
Thirteen eyes (44.8%) had previous glaucoma surgery, and 10
(34.6%) were known to have advanced glaucoma at the time of
keratoprosthesis surgery.
Concomitant Procedures
Procedures performed at the same time as Boston
keratoprosthesis type II implantation are summarized in
Table 2. Of the 29 eyes that underwent surgery, 11 eyes
(37.9%) had lens extraction and 4 eyes (13.8%) additionally
underwent anterior vitrectomy. Ten eyes (34.5%) had a tube
shunt placed for glaucoma: 7 eyes (24.1%) with SJS/TEN that
had not previously undergone glaucoma surgery and 3 eyes
(10.4%) with MMP that had previous tube implants. Nine eyes
(31.0%) had concurrent pars plana vitrectomy.
Visual Acuity Outcomes
Visual acuity after surgery improved to 20/200 or better
in 23 eyes (79.3%) (Table 3). Ten eyes (34.5%) recovered
a visual acuity of 20/30 or better. Cumulative functional
success, defined as the ratio of the cumulative years with visual
acuity of 20/200 or better to total duration of time since
surgery (Table 4), was calculated for those patients who
achieved at least 20/200 for each subgroup. Patients with
SJS/TEN had a higher cumulative functional success (0.91)
than those with MMP (0.64) or other ocular surface disease
(0.45). In those patients with 1 year of follow-up (n = 21;
overall mean follow-up time, 3.7 6 2.8 years), visual acuity of
20/200 or better was maintained in 12 eyes (57.1%). Thirteen
eyes were followed-up for more than 5 years, and 6 (46.2%)
had visual acuity of 20/200 or better at the last examination
(Fig. 2). Visual acuity was maintained beyond the average
TABLE 2. Concomitant Procedures Performed With Boston
Keratoprosthesis Type II Implantation
Concomitant
Procedures
Lensectomy
Lensectomy/vitrectomy
Pars plana vitrectomy
IOL removal
IOL insertion
Iridectomy
Tube shunt
Other (blepharoplasty)
MMP,
n (%)
5
1
8
2
1
2
3
4
(33.3)
(6.7)
(58.3)
(13.3)
(6.7)
(13.3)
(20.0)
(26.7)
IOL, intraocular lens.
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SJS/TEN,
n (%)
4
3
1
0
2
4
7
0
(33.3)
(25.0)
(8.3)
(0)
(16.7)
(33.3)
(58.3)
(0)
Other,
n (%)
2
0
0
0
1
1
0
1
(100.0)
(0)
(0)
(0)
(50.0)
(50.0)
(0)
(50.0)
Total,
n (%)
11
4
9
2
4
7
10
5
(37.9)
(13.8)
(31.0)
(6.9)
(13.8)
(24.1)
(34.5)
(17.2)
follow-up times (MMP 3.3 years and SJS/TEN 4.2 years) in 2
eyes (13.3%) with MMP and in 4 eyes (33.3%) with SJS/TEN.
Six eyes (20.7%) of 29 did not improve to at least 20/200
because of preexisting conditions. In eyes with SJS/TEN (n =
4), end-stage glaucoma (n = 1), occult retinal detachment (n =
1), and age-related macular degeneration (n = 2) were the main
reasons for failure to improve to 20/200, whereas occult retinal
detachment was the cause in 1 eye with MMP. The cause could
not be determined by chart review in 1 eye with MMP.
Postoperative Complications
and Management
Retroprosthetic membranes were the most common
complication after type II keratoprosthesis implantation. Fourteen
eyes (48.3%) required treatment with the neodymium-doped
Nd:YAG laser for a total of 17 procedures. One eye required
surgical membranectomy. Eight eyes (27.6%) had retinal detachment develop; 3 eyes (10.3%) underwent retinal detachment
repair. The mean time (in years) to retinal detachment could
be accurately assessed in 6 eyes and was longer in MMP (n = 2;
6.1 6 0.67 years) than in SJS/TEN (n = 4; 3.8 6 1.81 years).
Two SJS/TEN patients had retinal detachment develop after
replacement of the first keratoprosthesis or tectonic corneal patch
graft (revision surgery). One patient had endophthalmitis develop
on the fourth postoperative day after type II implantation and
underwent pars plana vitrectomy and injection of intraocular
antimicrobial medications, but that patient never regained useful
vision. Details of other complications and procedures are listed in
Tables 5 and 6, respectively.
Nine eyes (60%) with MMP and 6 eyes (50.0%) with
SJS/TEN retained the device without requiring reimplantation
or repair before their last follow-up (Fig. 3). Eight eyes (53.3%)
with MMP required either reimplantation of the keratoprosthesis
(n = 5; mean follow-up time, 3.5 6 1.7 years) or corneal patch
graft repair (n = 2; mean follow-up time, 1.1 6 0.4 years).
Similarly, 6 eyes (50.0%) with SJS/TEN required either
reimplantation (n = 5; mean follow-up time, 4.0 6 1.4 years)
or corneal patch graft repair (n = 1; follow-up time, 4 years).
One eye (8.3%) with SJS/TEN required a second reimplantation
of the keratoprosthesis. Of 6 eyes (MMP = 2, SJS/TEN = 4) that
had 20/200 or better vision for more than 5 years, 3 required
replacement or revision surgery. Ten of the 29 eyes (34.5%) had
a wound leak develop after a mean of 3.4 6 2.25 years after
primary implantation of the Boston keratoprosthesis type II.
Eyes afflicted with MMP had wound leaks develop earlier
(n = 4, 2.9 6 1.78 years) than in those with SJS/TEN (n = 6,
3.7 6 2.63 years), but there was no statistically significant
difference between the mean times to wound leaks between the
groups (P = 0.59). Eight of the 10 eyes that had wound leaks
develop underwent subsequent surgery; the implant fully
extruded in 1 eye, and all visual potential was lost before
repair could be attempted. One eye (3.5%) had recurrent leak
develop after the first repair. Three eyes (10.4%) presented with
early extrusion of the implant, and it is presumed that they had
wound leaks develop between follow-up visits. Of the total of 29
eyes, 12 eyes (41.4%) either underwent reimplantation of the
keratoprosthesis or experienced partial or total extrusion of their
keratoprosthesis during a total follow-up time of 107.9 years,
corresponding to a hazard rate of 0.11 per person-year.
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Cornea Volume 30, Number 12, December 2011
Boston Keratoprosthesis Type II Implantation
TABLE 3. Preoperative and Postoperative Best-Corrected
Visual Acuity After Boston Keratoprosthesis Type
II Implantation
One Year
At Last
Preoperative, Postoperative, Postoperative, Examination,
BCVA ($)
n (%)
n (%)*
n (%)
n (%)
20/20
20/25
20/30
20/40
20/50
20/60
20/70
20/80
20/100
20/200
20/400
CF
HM
LP
1
4
9
15
—
—
(3.4)
—
—
—
—
—
—
—
—
(13.8)
(31)
(51.7)
8 (27.5)
1 (3.4)
1 (3.4)
—
4 (13.8)
1 (3.4)
1 (3.4)
5 (17.2)
—
2 (6.9)
1 (3.4)
2 (6.9)
1 (3.4)
2 (6.9)
3
3
1
2
2
1
3
1
5
(10.3)
(10.3)
(3.5)
(6.9)
—
—
(6.9)
—
—
(3.4)
(10.3)
—
(3.4)
(17.2)
1 (3.4)
—
4 (13.8)
—
2 (6.9)
—
—
1 (3.4)
—
1 (3.4)
1 (3.4)
4 (13.8)
2 (6.9)
13 (44.8)
FIGURE 2. Kaplan–Meier survival curve for retention of 20/200
vision or better after Boston keratoprosthesis type II implantation, by preoperative diagnosis.
essentially zero. In a subsequent study conducted between
2000 and 2005 in SJS/TEN eyes (n = 16) at our institution
(some of these patients are included in our study) by Sayegh
et al,9 visual acuity of 20/200 or better was maintained for
a mean period of 2.5 6 2.0 years in 12 eyes (75%). In our
study, 6 eyes (50.0%) with MMP and 5 eyes (62.5%) with
SJS/TEN that achieved a vision of 20/200 or better maintained
it for more than 2 years. The results of our study are difficult to
compare with those previously published because patients in
previous studies were not categorized by the type of Boston
keratoprosthesis.
Glaucoma is an important problem after implantation
of a Boston keratoprosthesis.11,12 Preexisting glaucoma may
worsen after surgery, especially in eyes with chronic inflammation. Furthermore, eyes with no history of glaucoma
may have elevated pressures develop because of subsequent
inflammation and progressive angle closure from peripheral
anterior synechiae. A total of 20 eyes (70.0%) in our study had
a glaucoma drainage device implant before or at the time of
first implantation of a Boston keratoprosthesis type II. Despite
these efforts, 2 eyes (9.1%) that achieved 20/200 or better did
not maintain the improvement because of progressive
glaucoma. Because of increased ocular rigidity after keratoprosthesis implantation, currently available instrumentation
does not accurately detect intraocular pressure, and digital
palpation remains the best method in such eyes. Serial
evaluations of the optic nerve and visual fields are important
when possible.3 Oral medications may be the only effective
way to treat elevated intraocular pressure in eyes immediately
after Boston keratoprosthesis type II, followed by placement of
an Ahmed valve or cyclophotocoagulation if medical treatment
fails. Unfortunately, postoperative glaucoma procedures, such
The patient with preoperative visual acuity of 20/30 had a Boston keratoprosthesis type I
implant but had complications necessitating replacement with a keratoprosthesis type II.
*BCVA at any time after surgery.
BCVA, best-corrected visual acuity; CF, count fingers; HM, hand motion; LP, light
perception.
A search for factors affecting postoperative wound leak
after Boston keratoprosthesis type II implantation using
multiple regression analysis (including age at surgery, sex,
type of ocular inflammation, preceding glaucoma surgery, and
previous Boston keratoprosthesis type I surgery) did not show
any statistically significant associations. One must interpret
these results with caution given the small size and limited
number of variables in this retrospective study.
DISCUSSION
This is the first reported study to our knowledge focused
specifically on the long-term outcomes after implantation of
the Boston keratoprosthesis type II. Reported success rates for
implantation of a Boston keratoprosthesis (either type I or II)
in high-risk patients with severe ocular surface diseases, such
as MMP, SJS/TEN, and chemical burns, have been moderate.
Yaghouti et al11 in 2000 reported success in maintaining at
least 20/200 vision after 2 years of follow-up after Boston
keratoprosthesis implantation in eyes with MMP, SJS/TEN,
and chemical burns at 72%, 33%, and 64%, respectively; after
5 years of follow-up for SJS/TEN patients, the success rate was
TABLE 4. Eyes That Lost 20/200 Visual Acuity After Boston Keratoprosthesis Type II Implantation
No. Eyes
Preoperative Diagnosis
MMP
SJS/TEN
Other
Cumulative Years
Total
No. That Failed to
Retain 20/200 or Better Acuity
Postoperative
With Acuity of
20/200 or Better
13
8
2
9
3
2
46.4
32.8
7.6
27.3
29.7
3.4
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Cornea Volume 30, Number 12, December 2011
Pujari et al
TABLE 5. Complications Leading to Loss of More Than 20/
200 Visual Acuity After Boston Keratoprosthesis Type
II Implantation
Type of Complication
MMP
SJS/TEN
Other
Endophthalmitis
End-stage glaucoma
Retinal detachment
Choroidal detachment
Unknown
0
1
3
2
3
1
0
1
0
1
0
1
0
0
1
Total No. Eyes (%)
1
2
4
2
5
(4.3)
(8.7)
(17.4)
(8.7)
(21.7)
Total number of eyes (n) = 23.
as valve implant or cyclophotocoagulation, necessitate opening
the medial and lateral tarsorrhaphies to expose the globe,
which can be difficult because of the loss of normal tissue
planes after the union of ocular surface and eyelid submucosal
tissues. Preplacement of a glaucoma drainage device during
primary Boston keratoprosthesis type II may be justified given
the risk of glaucoma in such cases, but existing drainage
devices may not function well in the absence of conjunctiva.
Autoimmune diseases remain the worst prognostic
category for Boston keratoprosthesis implantation because
of ongoing ocular inflammation leading to tissue necrosis and
melting, which can result in leakage, choroidal effusion, and
even retinal detachment.13 Retroprosthetic membrane (48.3%)
was the most common complication in patients in our study,
and it can be managed conservatively with laser membranectomy in most cases. However, retinal and choroidal detachments (26.1%) together were the most common causes for the
failure to maintain visual acuity of 20/200 or better. A previous
study of outcomes after Boston keratoprosthesis type I
reported a retinal detachment rate of 3.5% (n = 141).3 In an
article reporting vitreoretinal complications after Boston
keratoprosthesis types I and II, the retinal detachment rate
was 12% (n = 110).13 Such differences may be related to the
type of Boston keratoprosthesis or the specific indications for
surgery or both. We speculate that chronic inflammation in
patients with autoimmune disease contributes to vitreoretinal
traction and subsequent retinal detachment.
Eyes with MMP and SJS/TEN are equally prone to
development of tissue melts, potentially requiring revision or
replacement. The introduction of vancomycin eyedrops to the
postoperative keratoprosthesis regimen has significantly
reduced the risk of stromal infection by Gram-positive bacteria
and also has reduced the rate of endopthalmitis,8 but the
numbers of patients are too low to determine a positive effect
of vancomycin in Boston keratoprosthesis type II patients. One
eye in our study with SJS/TEN had severe culture-negative
endophthalmitis develop, and the vision could not be salvaged,
despite aggressive treatment; tissue melt was a possible
predisposing factor. Regular examinations with aggressive
management of tissue melts are particularly important for
patients with a type II Boston keratoprosthesis. As the
pathogenesis of MMP and SJS/TEN becomes better understood, newer immunomodulating agents14–16 may be found
to enhance retention. Various methods to achieve biointegration of the keratoprosthesis in the future may also reduce tissue
melts and increase retention rates.17
Our study comes with certain caveats. We have no data
regarding which patients should receive a Boston keratoprosthesis type II versus a type I. Patients with cicatricial ocular
surface disease and corneal blindness are generally considered
for a Boston keratoprosthesis type II when a significant loss of
conjunctival fornices, extensive symblepharon, severe aqueous tear deficiency, and/or ocular surface keratinization make
type I surgery seemingly unlikely to succeed. The inability to
wear a contact lens because of forniceal foreshortening can be
a reason for the failure of a type I keratoprosthesis and
eventual replacement with the type II. The data in our modest
patient series also were insufficient, and the patient population
was too heterogeneous to determine the potential roles of total
iridectomy, vitrectomy, and intentional aphakia in successful
outcomes after keratoprosthesis implantation. Finally, comparisons between the Boston keratoprosthesis type II and other
types of keratoprosthesis currently in use around the world for
those with severe cicatricial blindness18,19 are difficult because
of differences in underlying patient populations and environment and ongoing incremental improvements over the past
decade in the Boston keratoprosthesis device. Implantation of
the Boston type II keratoprosthesis may be technically easier
than other methods in such patients. Perhaps, in the future,
diverse keratoprosthesis devices can be directly compared
among similar patients in the same clinical center.
In conclusion, Boston keratoprosthesis type II implantation in selected patients can provide sustained recovery
of vision. However, challenges clearly remain. Type II
keratoprosthesis complications may be reduced by further
advances in device design and materials, new approaches to
TABLE 6. Additional Procedures Required After Boston Keratoprosthesis Type II Implantation
Procedures
Nd:YAG laser retroprosthetic membranectomy
Surgical retroprosthetic membranectomy
Tube shunt
Wound leak repair
Retinal detachment repair
Skin revision*
MMP, Eyes
(No. Procedures)
6
1
0
4
1
5
(8)
(1)
(0)
(5)
(1)
(7)
SJS/TEN, Eyes
(No. Procedures)
6
0
2
5
2
4
(7)
(0)
(2)
(7)
(2)
(9)
Other, Eyes
(No. Procedures)
2
0
0
0
0
1
(2)
(0)
(0)
(0)
(0)
(1)
Total, Eyes
(No. Procedures; %)*
14
1
2
9
3
10
(17; 48.3)
(1; 3.5)
(2; 6.9)
(12; 31.0)
(3; 10.3)
(17; 34.5)
*Most common reason for skin revisions was skin overgrowth over the nub, causing visual impairment.
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Cornea Volume 30, Number 12, December 2011
FIGURE 3. Kaplan–Meier survival curve for retention of first
Boston keratoprosthesis type II implant, by preoperative
diagnosis.
immunomodulatory therapy, improvements in perioperative
and postoperative care, and perhaps by a better appreciation
for higher-risk subgroups within the larger heading of
SJS/TEN and MMP patients.
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