Download Glaucoma Associated with Keratoprosthesis

Glaucoma
Peter A. Netland,
Associated with Keratoprosthesis
MD, PhD, Hisao Teruda, MD, Ches H. Dohlman,
MD, PhD
Objective:
This study aimed to review the authors clinical experience with glaucoma associated with keratoprosthesis in patients with severe cornea1 disease.
Design:
The study design was a retrospective review of case series.
Participants:
The authors studied 55 eyes in 52 patients with keratoprostheses
with follow-up of 21 ? 16
months (range, 3-77 months).
Intervention:
Glaucoma drainage devices were implanted in 36 eyes (35 Ahmed valves, 1 Krupin valve) with
21 ? 15 months’ follow-up (range, 3-64 months).
Main Outcome
Measures:
Clinical outcome assessment
included vision, intraocular pressure (IOP), visual
fields, optic disc appearance, and identification of complications.
Results:
Glaucoma was found in the majority (64%) of eyes treated with keratoprostheses,
identified in 20 eyes
(36%) before surgery and an additional 15 eyes (28%) after surgery. Of the 36 eyes treated with glaucoma drainage
devices, IOP was controlled in 29 eyes (81%), with 9 eyes (25%) requiring additional medications. Continued
progression of glaucoma occurred in 5 (14%) of 36 eyes with keratoprostheses
and glaucoma drainage implants (4 of
these eyes had advanced glaucomatous optic nerve damage before surgery). There were nine nonvision-threatening
complications due to drainage implants. Compared with the preoperative visual acuity, vision was markedly improved
in 63%, unchanged in 17%, and worse in 20% of eyes after keratoprosthesis
surgery.
Conclusion:
Elevation of IOP is common in patients with keratoprosthesis,
and prevention or treatment with
glaucoma drainage implants is effective. Ophthalmology 7998; 705757-757
Despite advances in transplantation techniques using human cornea, the prognosis for standard keratoplasty remains poor in patients with severe past or ongoing chronic
inflammation of the ocular surface. This poor prognosis
group includes patients with Stevens-Johnson
syndrome,
ocular cicatricial pemphigoid, end-stage dry eye, and severe chemical burns.‘,* In addition, some patients with
repeated graft failures due to immune reaction have a poor
prognosis for subsequent keratoplasty.
Keratoprosthesis
surgery is an alternative for visual rehabilitation of these
patients. However, earlier attempts using keratoprosthesis
in humans were plagued by precipitous and severe complications, usually related to necrosis of the tissue surrounding the prosthesis that could lead to leakage of aqueous, infection, or extrusion.
Recent improvements of techniques and modification
of the postoperative regimen have improved the prognosis
after keratoprosthesis
surgery.” Necrosis of the tissue
around the device and extrusion are now less common
because of temporary postoperative coverage of the de-
Originally
received:
June 2, 1997.
Revision accepted: September 18, 1997.
From the Department of Ophthalmology, Massachusetts Eye and Ear
Infirmary,
Harvard
Medical
School,
Boston,
Massachusetts.
Presented in part as a poster at the American Academy of Ophthalmology Annual Meeting, Chicago. Illinois, October, 1996.
Supported by Mr. Sa’ad A. A. Al-Rashed, Kuwait.
The authors have no propriety interest in the devices used In this study.
Reprint requests to Peter A. Netland, MD, PhD, The University of
Tennessee, Memphis,
Department
nue, Memphis,
TN 38163.
of Ophthalmology,
956 Court
Ave-
vice with conjunctiva or skin and topical administration
of collagenase inhibitors.4 Postoperative uveitis has been
minimized by use of moderate-dose steroid regimens.
Retroprosthesis membranes that form despite steroid
therapy generally are mild and may be opened with the
neodymium:yttrium-aluminum-garnet
laser.5 With reductions of these complications, other long-term visionthreatening problems have become more important, especially glaucoma.” The purpose of this study was to review
our own clinical experience with glaucoma in patients
with keratoprosthesesand to describe the useof glaucoma
drainage implants in this setting.
Methods
Patients treated with keratoprosthesis
and glaucoma
drainage
implant gave verbal consentand signedan informed consent
form approvedby the Institutional Review Board. Eyes with
keratoprostheses
were from a consecutive
series of cases per-
formed from March 1990to June 1996.No eyes with keratoprosthesis implanted during this period were excluded from the
analysis. Glaucoma drainage implants were performed in eyes
with keratoprosthesis from February 1991 to June 1996. The
surgical procedures have been described in detail elsewhere.’
The Dohlman-Doane
polymethylmethacrylate
keratoprosthesis type I or II was used in all patients.* The type I device was
used except in extremely dry eyes, in which the longer nub in
the type II design was used for a through-the-lid
approach. If
present, the lens was removed using extracapsular technique,
and total iridectomy often was performed. In patients with preexisting glaucoma or those with chronic inflammation and a
high risk of subsequently developing glaucoma, a glaucoma
drainage implant was included at the time of keratoprosthesis
Ophthalmology
Volume 10.5, Number 4, April 1998
Table 1. Patient Characteristics
Without Glaucoma
Drainage Implant
With Glaucoma
Drainage Implant
19
18
36
No. of eyes
No. of patients
Race [N (%)I
White
Black
Aslan
Indian
Arabic
24 (66)
5 (14)
1 (3)
Sex [N (%)I
Mean ? SD
Range
Follow-up
(mos)*
Mean ? SD
Range
Keratoprosthesls
design [N (%)I?
Type 1
Type II
Lens status [N (%)I
Pseudophakic
Aphakic
Adluncnve
surgical procedures [N (%)I
Vitrectomy
lridectomy
Lensectomy
Diagnosis [N (%)I$
SD = standard
2 (4)
4 (7)
(11)
21 (58)
15 (42)
28 (51)
27 (49)
64 + 22
24-93
63 + 18
26-91
64 i 19
24-93
t_ 17
t 15
21
4-77
? 16
21
3-64
3-77
16 (84)
3 (16)
18
18
(50)
(50)
34 (62)
21 (38)
1 (5)
18 (95)
4 (11)
32 (89)
5 (9)
50 (91)
18 (50)
21 (58)
27 (75)
24 (44)
27 (49)
37 (67)
15 (42)
18
7
13
3
14
6 (32)
6 (32)
10 (53)
Pemphigoid
6 (11)
1 (2)
7 (37)
12 (63)
21
3
1
5
3
7
Stevens-Johnson
Chemical burn
Herpetic keratitis
Graft failure
42 (76)
2 (6)
4
Age (yrs)
55
52
34
18 (95)
1 (5)
-
Male
Female
Total
(16)
(5)
6 (17)
(26)
8 (22)
0 (0)
(16)
(37)
7 (19)
(33)
(13)
(24)
(5)
(25)
deviation.
* Follow-up
period was until the most recent appomtment,
death (N = l), or keratoprosthesis
removal (N = 6), mcludmg retmal detachment
(N =
3) or enucleation
(N = 2). Patients wieh and without glaucoma dratnage Implants were not slgmficantly
different m their age or follow-up period (P
= 0.88 and 0.99, respectively,
unpaired t test).
t Patients
with
and without
glaucoma
drainage
implants
were slgnlficantly
dlfferent
(P = 0.013,
chi-square).
$ Patients
with
and without
glaucoma
drainage
Implants
were significantly
different
(P = 0.027,
chl-square).
surgery. In other patients who subsequently developed glaucoma, the device was implanted at a later time. The drainage
implant was preferentially positioned superotemporally
or superonasally. In one patient, a second Ahmed drainage implant
was positioned superotemporally
when the patient developed
progressive visual field changes after the keratoprosthesis procedure with the first drainage implant that had been positioned in
the superonasal quadrant. The implant tube and, in many patients, the device plate were covered with eye bank sclera. The
keratoprosthesis then was covered with conjunctiva (type I) or
lid skin (type II).
After surgery, a moderate-dose steroid regimen was used,
including topical, systemic, and, in particular, peribulbar routes
of administration.’
Eyes were imaged with B-mode ultrasound
during the immediate postoperative period. The conjunctiva or
skin was opened at approximately 2 months after surgery. Systemic oral antibiotics were administered during the immediate
postoperative period, and topical prophylactic antibiotics were
administered indefinitely after surgery. Anticollagenase medications, such as 1% medroxyprogesterone
and 1% tetracycline,
were used for months or years after surgery.
752
Visual Outcome
Improved
83%
Glaucoma
Present
84%
Figure 1. Summarv of visual outcome and glaucoma m eyes treated with
keratoprosthesls.
The visual ouecome was improved from hght perceptlon,
hand movements,
or finger counting to between 20/200 and 20/20 in the
majority
(63%) of eyes at the most recent follow-up
exammatlon
after
keratoprosthesls
surgery. Glaucoma, characterized
by consistently elevated
intraocular pressure or progressive glaucomatous changes of the vtsual field
and optic nerve head, was found m the malorlty (64%) of eyes. (Values
shown are the proportion
of all eyes with keratoprosthests,
n = 55.)
Netland et
al * Glaucoma
Associated
with
Keratoprosthesis
A
appearance of the Dohlman-Deane
keraroprostheses. A, type I keratoprosthesls
in the left eye of a patlent
wth a history of repeated graft fadure and glaucoma. The scleral patch graft covermg the aqueous shunt tube 1s vwble through the conlunctwa
In the
superonasal area B, type II keratoprosthesls
(through the hd) In a burn patlent. The aqueous shunt tube LSunder the hd skm and LSnot vwble.
Figure 2. Examples of the postoperatwe
The intraocular
pressure (IOP) was assessed before surgery
by tonopen, pneumotonometer, or tactile estimation, depending
on the severity of the cornea1 disease. After surgery, IOP was
assessed by tactile estimation by two independent observers
(PAN and CHD). The IOP was characterized as low, normal,
or elcvatcd (IOP > 21 mmHg was considcrcd elevated when
measurement by tonopen or pneumotonometer was possible).
Agreement between observers was found for all cases characterized as elevated. Visual fields were measured by automated
perimetry or Goldmann perimetry (the visual field extends to
up to 70” and 40” in eyes with keratoprosthesis type I and type
II, respectively). The optic nerve was assessed by stereophotography or by clinical biomicroscopic examination, which can be
performed through both the type I and type II keratoprostheses.
Glaucoma was defined as elevated IOP on at least two visits
or progressive glaucomatous changes of the visual field and
optic nerve head. In addition, four eyes in four patients were
found to have end-stage glaucomatous optic disc cupping and
visual field loss after the tissue covering the keratoprosthesis
was opened and were included in the glaucoma group. In some
cases, the anterior segment was examined using the ultrasound
biomicroscope (UBM, Humphrey Systems, San Leandro, CA).
However, many cases could not be assessed by UBM because
of the thickness of the overlying tissue.
The vision was light perception (21 eyes), hand movements
(24 eyes), or finger counting (10 eyes) in all patients before
surgery. The postoperative vision was considered improved if
the Snellen visual acuity was in the range between 201200 to
20120. The vision was considered the same if the vision was
unchanged or did not improve to between 201200 and 2Of20.
The vision was considered worse if there was any change in
the following order: finger counting, to hand movements, to
light perception, to no light perception.
Patients with keratoprostheses with and without glaucoma
drainage implants were compared using the unpaired t test and
the chi-square test. Probability values less than 0.05 were considered statistically significant.
Results
The characteristics of the patients are listed in Table 1. A total of
55 keratoprostheses were implanted in 52 patients. The mean ?
standard deviation age was 64 t 19 years, with a range of 24 to
93 years. The follow-up period was 21 2 16 months, with a range
of 3 to 77 months. Glaucoma drainage devices were implanted in
36 eyes (65% of total) in 34 patients (65% of total). The type of
keratoprosthesis was significantly different in the patients with and
Table 2. Patients with Keratoprosthesls Treated with Glaucoma
Draillage Implant
No of eyes*
No of patients
Type of Implant [N (%)]
Ahmed valve
Krupm valve
Locxlon of Implant [N (%)I
Superotemporal
Superonasdl
lnferotemporal
Tlmlng of Implant [N (%)I
With keratoprostheala
After keratoprosthesrs
Antenor chamber dnglet [N (%)I
Open
Closed
Unknown
Postoperative IOP [N (%)I
Low or nonet
Normal
Elevated
Postoperatwe progressmn of
glaucoma [N (%)I$
Postoperatwe
medlcanona
[N (%)I
36
34
35 (95)
1 (5)
16 (44)
19 (53)
1 (3)
29 (81)
7 (19)
5 (14)
3 (8)
28 (78)
5 (14)
29 (81)
2 (6)
5 (14)
9 (25)
* One eye had a second Ahmed glaucoma dramage Implant poaltmned
superotemporally
for progressmn of glaucoma, which was not Included m
the analysla m this table.
t Includes preoperatwe assessment and postoperauve
sound hmnucroscope (UAM).
evaluation
by ultra-
$ Inrraocular pressure (IOP) at most recent follow-up
“Low or none”
Includes three patients who had keratoprosthesls
removal due to ussue
necroslb or mfectwn and two patwnts wth ret&
detachment.
§ Progresswn of glaucoma by elevation of mtraocular pressure or changes
of the waudl field and optic nerve head. The majority of these eyes (4 of
5, 80%) had pre-exlstmg glauconu wrth advanced optic nerve damage.
753
Ophthalmology
Volume105,Number4, April 1998
Figure 3. Ultrasound biomicroscopy in a patient with keratoprosthesis
and glaucoma. The anterior chamber anele (asterisk) is ooen. The iris and
retroprosthesls membrane form a smgle sheet (arrow) that 1sadherent to
the ciliary body (cb) at one end and the keratoprosthesis at the other. C
= cornea; the central area of the cornea (not shown) contains the type
I keratoprosthesis.
without glaucoma drainage implants (P = 0.013, &i-square), with
the type II through-the-lid keratoprosthesis used in a greater proportion of the patients with glaucoma drainage devices (50%)
compared with those without such devices (16%). Comparison of
the diagnoses between the patients with and without glaucoma
drainage implants was significantly different (P = 0.027, chisquare). A greater proportion of patients with pemphigoid and
Stevens-Johnson syndrome were treated with glaucoma drainage
implants, whereas patients with herpetic keratitis or graft failure
were more likely to have been treated without glaucoma drainage
devices. The proportion of patients with chemical bums was similar in patients with and without glaucoma drainage implants (22%
and 26%, respectively).
As shown in Figure 1, the postoperative vision was improved
to between 20/200 and 20120 from the preoperative vision (light
perception, hand movements, finger counting) in the majority
(63%) of the 55 eyes treated with keratoprosthesis. The postoperative vision was the same or only slightly improved in 17% and
worse in 20%, including those eyes that developed vision-threatening postoperative complications. Glaucoma was found in the majority of eyes (64%) treated with keratoprosthesis, occurring before
surgery in 36% of eyes and after surgery in another 28% of eyes
(Fig 1). In a minority of eyes (36%), no evidence of glaucoma
was found before surgery or during the postoperative follow-up
period. Examples of the postoperative appearance of the type I
and type II keratoprostheses are shown in Figure 2.
Of the patients with keratoprosthesis and glaucoma drainage
implant, the majority of implants were Ahmed valves (9.5%), and
most (97%) were positioned in the superior quadrants (Table 2).
The majority of patients (81%) had glaucoma drainage devices
implanted at the same time as the keratoprosthesis; however, 19%
of patients underwent two separate procedures, with later glaucoma
drainage device implantation for the treatment of postkeratoprosthesis glaucoma. Although the angle was not examined in the majority of patients (78%), preoperative assessment and postoperative
754
evaluation by ultrasound biomicroscopy showed an open angle in
14% and a closed angle in 8% of eyes (Fig 3). In patients with
functioning glaucoma drainage implants, B-mode ultrasound
showed a collection of fluid (aqueous) in the pseudocyst around
the drainage implant plate (Fig 4).
The postoperative IOP by tactile estimation was normal in 81%
and elevated in 6% of eyes (Table 2). The IOP was low or none
in 14% (5 eyes), including three patients who had keratoprosthesis
removal due to tissue necrosis or infection and two patients with
retinal detachment. Postoperative antiglaucoma medications were
used in 25% of eyes, usually systemic carbonic anhydrase inhibitors, for treatment of elevated IOP or progressive visual field or
optic nerve changes in the eye with the keratoprosthesis or the
fellow eye. Despite the use of drainage implants, postoperative
elevation of IOP or progressive glaucomatous visual field and optic
nerve head changes were observed in five eyes (14%). Most of
these eyes (4 of 5, 80%) with progressive glaucoma after surgery
had advanced glaucomatous optic nerve damage before placement
of the glaucoma drainage implant (Fig 5).
As listed in Table 3, there were nine complications attributable
to the glaucoma drainage implants in five separate eyes (14% of
eyes with drainage implants). The most common complication was
obstruction of the tube, which occurred in four eyes (11%). Of
the patients who developed blocked tubes, two tubes were repaired
surgically and two were treated with antiglaucoma medications.
Erosion of the conjunctiva and the scleral patch graft over the tube
was found in one eye (3%). This required several revisions with
scleral and pericardial patch grafts, which ultimately resulted in
stable coverage of the tube. The B-mode ultrasound performed
during the immediate postoperative period showed three eyes with
anterior choroidal effusions and one eye with limited suprachoroida1 hemorrhage, all of which resolved without clinical sequelae.
In the eyes with keratoprosthesis and drainage implant, several
vision-threatening complications developed that were not attributed to the drainage implant. These included two eyes with retinal
detachment, two eyes with retinal detachment and infection, and
one eye with infection, which required removal of the keratoprosthesis in three eyes.
Discussion
Keratoprosthesis
may be the only option for visual rehabilitation
of certain patients with severe ocular surface
Figure 4. A B-mode ultrasound m a patlent wth keratoprosthesls and
glaucoma dramage Implant. A collectmn of low-echogemc flutd (aqueous)
IS present wthm the pseudocyst around the glaucoma dramage Implant
plate (arrow).
Netland et al * Glaucoma Associated with Keratoprosthesis
Intermittent responses to V&E
disease, including those with ocular cicatricial pemphigoid, Stevens-Johnson syndrome, end-stage dry eye, severe chemical burns, and repeated failure of penetrating
keratoplasty. However, these patients may have a high
incidence of glaucoma even before keratoprosthesis implantation. In a series of 111 patients (none with keratoprosthesis) with ocular cicatricial pemphigoid, 29 patients
(26%) were found to have glaucoma, mostly in the ad-
& SC
Figure 5. Progressive visual
field loss in a patient with keratoprosthesis
and glaucoma
drainage implant. A 61-yearold man with bilateral blmdness due to chemical burn and
elevated mtraocular
pressure
was treated with type I keratoprosthesis
and an Ahmed
valve placed m the superonasal area. After surgery, the
tactile estimation
of the intraocular pressure was Judged
to be 15 to 20 mmHg. After
opening the conlunctiva
over
the keratoprosthesis
optic,
Goldmann
perimetry
showed
advanced
glaucomatom
vrsual field loss (A). Six months
later, the visual field had
worsened
despite treatment
with systemic carbonic anhydrase inhibitors
(B). A second Ahmed glaucoma valve
was implanted
supertemporally, and 6 months later, the
field had not worsened.
vanced stage.” We found glaucoma before surgery in 36%
of eyes in our patient population.
The long-term problem of glaucoma after keratoprosthesis implantation is becoming increasingly recognized. At a meeting of the Keratoprosthesis Study Group
in 1992, the moderator expressed the general consensus
that “a major disappointment was the frequency of intractable glaucoma, resulting in loss of vision after prelimi-
755
Ophthalmology
Table
3. Complications
Associated
Implant
in Patients with
with Glaucoma
Keratoprosthesis*
Volume 10.5, Number 4, A@
Drainage
No. (%)
Blocked tube?
Erosion of conjunctiva
over tube and aqueous leak
Choroidal
effusion$
Suprachoroidal
hemorrhage+
4
1
3
1
Total
9 (25)
complications
(11)
(3)
(8)
(3)
* Total N = 36. Complications
in this group that were not attributable
to the glaucoma drainage implant included three patients with removal
of keratoprosthesis
(one retinal detachment,
one infection
with retinal
detachment,
and one Infection)
and two others with retmal detachment
(one following infecnon).
t Of the patients with obstructed tubes postoperanvely,
two were repaired
surgically and two were treated with antiglaucoma
medications.
$ Observed
by B-mode
period; resolved without
ultrasound
sequelae.
during
the immediate
postoperative
nary success with a keratoprosthesis.“”
In a series of
osteo-odontokeratoprostheses,
41% of the patients had
glaucoma before surgery and another 33% developed it
after surgery.” Other investigators have discussed the
problem of glaucoma in eyes with keratoprosthesis.12.‘3
One report mentions the use of a small silicone tube for
treatment of intractable glaucoma.14 Without treatment
of postoperative glaucoma, the long-term prognosis for
preservation of vision is poor for many patients with keratoprosthesis.
In addition to the eyes with glaucoma before keratoprosthesis, we also observed the postoperative appearance
of glaucoma in another 28% of eyes, bringing the prevalence of glaucoma to approximately two thirds in eyes
with keratoprosthesis. In our clinical experience, we
found that a glaucoma drainage device can be readily
implanted together with a keratoprosthesis or at a later
date. Glaucoma drainage implants prevent the severe elevation of IOP that occurs in some patients treated with
keratoprosthesis alone. Postoperative complications attributable to glaucoma drainage implants have not been
common in our patients with keratoprosthesis. Although
progression of end-stage glaucoma can occur despite use
of glaucoma drainage implants, these implants are effective in reducing the IOP and preventing glaucomatous
optic nerve or visual field changes in the majority of
patients.
In eyes with keratoprosthesis and glaucoma, we observed both open angles and angles closed due to formation of peripheral anterior synechiae by preoperative assessment using biomicroscopy and postoperative evaluation using ultrasound biomicroscopy. Total removal of
the iris during keratoprosthesis surgery was intended to
decrease the likelihood of subsequent secondary angleclosure glaucoma. However, glaucoma was not eliminated in 21 (58%) of the 36 eyes treated with total removal
of the iris during the surgical procedure. It is likely that
multiple mechanisms of glaucoma, including both openand closed-angle mechanisms, can occur in glaucoma as756
1998
sociated with keratoprosthesis, which may be comparable
to the heterogeneous causes of glaucoma associated with
penetrating keratoplasty.”
In our patients with keratoprosthesis and glaucoma,
treatment with glaucoma drainage implants effectively
reduced the IOP in nearly all patients, some requiring
additional antiglaucoma medications. Because topical
antiglaucoma medications are of little or no use in these
patients, systemic carbonic anhydrase inhibitors were
preferentially used when medical therapy was required to
further reduce the IOP. Cyclodestructive procedures have
been recommended in the past for patients with keratoprosthesis and elevated IOP, and pars plana filter has
been recommended for select patients.6 In our patients,
however, filtration surgery usually was not possible because of complete removal of conjunctiva in type II
through-the-lid keratoprosthesis or severely scarred conjunctiva in type I keratoprosthesis procedures.
Complications directly attributable to the glaucoma
drainage implant developed in nine eyes (25%) in patients
with keratoprosthesis and drainage implant. The majority
of patients were treated with the Ahmed valve, in which
a tapered chamber valve provides resistance to aqueous
flow. This implant is associated with fewer complications
of overfiltration in the immediate postoperative period
compared with other drainage devices.16 The complications in our patients were repaired surgically or treated
medically. Our complication rate may have been relatively low because of the aqueous flow-resistance of the
Ahmed valve, adequate coverage of the drainage devices
with sclera and in many instances skin, and the removal
of intraocular contents (lens, vitreous, and iris) that could
potentially block the tube. We did not assess these patients
for motility disturbances, which, if found, could be caused
by multiple factors and would be of little or no functional
significance for the patient. Focal or diffuse cornea1
edema, which can account for nearly one fifth of the
complications after glaucoma drainage implants,17 cannot
occur after replacement of the cornea with the polymethylmethacrylate keratoprosthesis.
We observed continued progression of glaucoma in 5
(14%) of 36 eyes with keratoprosthesis and glaucoma
drainage implant. The majority of these eyes (4 of 5)
with progressive postkeratoprosthesis glaucoma had preexisting glaucoma with advanced glaucomatous optic
nerve damage, which had been obscured from view before
surgery. In the eyes with elevation of IOP despite drainage
device implantation (2 of 5), this may have been caused
by increased resistance to aqueous flow through the pseudocapsule around the drainage implant plate, unrecognized blocked tube, or other failures of the drainage implant procedure. In eyes with continued optic nerve or
visual field changes and apparently normal IOP (3 of 5),
there may have been unrecognized elevation of the IOP
or intermittent elevation of the IOP, which could occur
with episodes of uveitis. In addition, the eyes with preexisting glaucomatous damage may have been abnormally sensitive to otherwise normal levels of IOP, which
has been termed “low-tension glaucoma equivalent.” ‘*
A limitation of our study was that IOP was difficult
Netland et al * Glaucoma Associated with Keratoprosthesis
to measure, particularly in those patients with type II
through-the-lid
keratoprosthesis.
Although the McKayMarg tonometer used on the sclera has been suggested,6
we have found use of tonometers of little value after type
I keratoprosthesis
and of no value after type II keratoprosthesis. Attempts to use the pneumotonometer and the
tonopen on the sclera of our patients with type I keratoprosthesis showed considerable overestimation
of the
IOP. In our patients with keratoprosthesis,
digital palpation of the globe was the most practical available method
for assessment of IOP.
Despite its uncertainties, digital palpation of the globe
is useful for identifying a marked increase of the IOP. In
a study of tactile assessment of 138 eyes, palpation did
not indicate an IOP greater than 30 mmHg for any eye
in which the applanation pressure was below 30 mmHg.lg
However, palpation did not identify two (29%) of seven
of eyes with an applanation pressure greater than 30
mmHg.lg This degree of failure to detect elevated IOP by
digital palpation could have influenced the success rate
after glaucoma drainage implant determined in our study
of eyes with keratoprosthesis.
Up to 8 (29%) of 29 “successes” in our study of eyes with keratoprosthesis
and
drainage implants actually may have had elevated IOP,
which would decrease the success rate from 81% (29 of
36 eyes) to 58% (21 of 36 eyes).
In conclusion, preoperative elevation of IOP is common in patients who are candidates for keratoprosthesis.
Many additional patients develop glaucoma after keratoprosthesis surgery. With improvements in management
of inflammatory and infectious complications of keratoprosthesis, glaucoma emerges as an important long-term
complication of this procedure. Glaucoma associated with
keratoprosthesis
is treated effectively
with glaucoma
drainage implants, which can control the IOP in most
patients, with some requiring additional antiglaucoma
medications. Progression of glaucoma can occur despite
use of glaucoma drainage implants, usually in patients
with advanced glaucomatous optic nerve damage. Postoperative monitoring of the optic nerve and visual field is,
therefore, recommended even in those patients with keratoprosthesis who have been treated with glaucoma drainage implants.
Acknowledgment.
The authors thank Dr. C. Stephen Foster for patient referrals.
References
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2. Soong HK. In: Krachmer JH, Mannis MJ, Holland EJ, eds.
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Cornea: Surgery of the Cornea and Conjunctiva. St. Louis,
Missouri: Mosby-Year Book, Inc, 1997; chap. 145, pp.
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