ABSTRACT
Objective: To report a previously unpublished complication of CyPass® glaucoma stent placement in a patient undergoing combined cataract and glaucoma surgeries. This case occurred prior to voluntary withdrawal of the CyPass® device from the market.
Case Description: A 70-year-old Hispanic male with a history of advanced pseudoexfoliation glaucoma left eye (OS) > right eye (OD) presented to the North Texas Veterans Affairs Medical Center with disease progression despite escalation to maximum medical therapy. His maximum intra-ocular pressure (IOP) prior to treatment was 29 mm Hg in OD and 60 mm Hg in OS. Given the presence of a visually significant cataract in OS with advanced glaucoma that was progressing despite maximum medical therapy, a decision was made to pursue cataract phacoemulsification in conjunction with insertion of a CyPass® stent device in OS. The patient was consented prior to surgery. Postoperatively, his IOP dropped to as low as 4 mm Hg, followed by hyphema as well as a dense vitreous hemorrhage. Appropriate placement of the stent was confirmed by ultrasound biomicroscopy, gonioscopy, and anterior segment optical coherence tomography (OCT). The hypotony, hyphema and vitreous hemorrhage all resolved with conservative medical management by the time the patient was seen again one month later.
Conclusions: It is important for surgeons to be aware of even less common complications of micro invasive glaucoma surgery (MIGS) procedures. In our case, the patient developed a complication that had previously not been described. While this case resolved with conservative medical management, this case illustrates that it is important to appropriately assess pre-operative risk factors and confirm appropriate placement of a MIGS device postoperatively.
Keywords: CyPass®, vitreous hemorrhage, minimally invasive glaucoma surgery.
JRMS August 2020; 27(2): 10.12816/0055813
Introduction
Previously, when advanced glaucoma necessitated the use of incisional surgery to achieve better IOP control, fewer options were available, which included filtering and tube shunt procedures (1). However, over the past several years, a new class of surgeries – termed minimally invasive glaucoma surgery (MIGS) – have emerged which share five common advantageous
Qualities,
as described by Saheb and Ahmed (2): minimal trauma to the target
tissue, ab interno clear corneal approach, IOP lowering ability, high safety profile,
and rapid recovery time. Some of the primary stent technologies currently
approved for use in the US are the iStent® (Glaukos, Laguna Hills,
CA, USA), and XEN® stent (Allergan plc, Dublin, Ireland). The iStent®
bypasses the trabecular meshwork and is inserted directly into Schlemm’s canal.
Finally, the XEN® stent drains aqueous humor into the subconjunctival
space. (2).
Of particular interest to us in this case
study is the CyPass® device (Figure 1) (3), which was
used in conjunction with cataract surgery. The CyPass® created a
conduit for outflow into the suprachoroidal space. The stent was made of flexible polyimide material containing 64 fenestrations and is
injected just below the junction of the scleral spur and the ciliary body. There is currently a large,
multi-center, randomized controlled trial – the COMPASS trial – studying the
safety and efficacy of this device (3). The published two-year
results detailed multiple adverse side effects, including subconjunctival
hemorrhage and hyphema (3). More recently, the device was
voluntarily withdrawn by the manufacturer due to the five-year data
demonstrating a significantly higher rate of endothelial cell loss (4).
However, previously there had been no reports of vitreous hemorrhage following
CyPass® stent implantation. In this report, we aim to detail
perioperative factors which may have contributed to the patient’s postoperative
course.
Figure 1: Gonioscopic view of CyPass Stent device.
Case Report
Our patient was a 70-year-old Hispanic male who
presented to the North Texas Veterans Affairs Medical Center in August 2017, with
a history of advanced pseudoexfoliation glaucoma (OS > OD). His glaucoma
progressed despite adherence to maximum medical therapy. Maximum pre-treatment IOP
was 29 mm Hg OD and 60 mm Hg OS. Gonioscopy confirmed open angles in both eyes (OU).
At the time of presentation, he was already on a regimen of latanoprost 0.005% (Xalatan®)
at bedtime (qhs) OU, dorzolamide-timolol 2%,0.5% (Cosopt®) twice
a day (BID) OU, and brimonidine 0.2% (Alphagan®) three times a day (TID)
OU, and acetazolamide (Diamox®) 250 mg four times a day orally (QID).
The only other intervention prior to incisional surgery was selective laser
trabeculoplasty (SLT) of the left eye in December 2016.
Visual fields by Humphrey Field Analyzer 3
(Humphrey Instruments, CA, USA) were unremarkable in the right eye (central 24-2
threshold test) and showed significant global depression in the left eye (central
10-2 threshold test), revealed significant progression from central island (Figure
2A).
OCT
of the retinal nerve fiber layer performed in June 2017 was borderline (average
of 86 µm) in the right eye and showed significant diffuse thinning in the left
eye (average of 27 µm) (Figure 2B).
Figure 2A
Figure
2B
Figure 2. Pre-operative glaucoma
testing.
(A)
Humphrey Visual Field testing
from 7/2017 and 11/2017. (B) OCT retinal nerve fiber layer images from 4/2016
and 6/2017.
In November 2017, patient’s right eye visual
acuity with spectacle correction was 6/9.5 (20/30) with evidence of 2+ nuclear
sclerotic and 2+ cortical cataract. In his left eye, the visual acuity with
spectacle correction was 6/24 (20/80) pinhole to 6/19 (20/70) with evidence of 2+
relative afferent pupillary defect and 2+ nuclear sclerotic and cortical
cataract. Additionally, the left optic nerve was noted to have a cup to disc
ratio of 0.9, compared to 0.3 in the right eye. IOPs in the right and left eyes
had stabilized to 14 mm Hg and 15 mm Hg, respectively. Given the presence of a
visually significant cataract in the left eye with advanced progressive glaucoma,
a decision was made to pursue cataract phacoemulsification in conjunction with
insertion of a CyPass® stent device.
In January 2018, the patient was consented
prior to surgery and underwent an uncomplicated cataract phacoemulsification
with insertion of an Alcon SN60WF 12.5D single piece intra-ocular lens into the
capsular bag as well as successful implantation of a CyPass® stent device into
the nasal angle. On postoperative day 1, the patient’s left eye vision was 6/60
(20/200) and his IOP was 6 mm Hg. The corneal exam was significant for 2+
stromal edema with 2+ Descemet’s folds, and the anterior chamber was noted to have
trace white blood cells as well as 4+ red blood cells with a layering 0.33 mm
hyphema. He was started on routine postoperative therapy which included 1%
prednisolone acetate (Pred-Forte®) four times a day, moxifloxacin
(Vigamox®) four time a day, and bacitracin zinc and
polymyxin B sulfate ophthalmic ointment
(Polysporin®) at night. On postoperative day 4, visual acuity had
worsened to light perception, and IOP had decreased to 4 mm Hg. Corneal edema
was stable and the layered hyphema had worsened to 1.5 mm. There was no view by
funduscopic exam, and so a B-scan was performed which did not reveal any
choroidal effusions. On postoperative day 11, visual acuity remained stable at
light perception and IOP had increased slightly to 5 mm Hg. Corneal and anterior
chamber exams were stable. There was still no view for a funduscopic exam, and
a repeat B-scan revealed a small new choroidal effusion with vitreous
hemorrhage. Atropine 1% twice a day was
initiated in the left eye, prednisolone was maintained at QID, and antibiotics
were stopped. At his postoperative week 3 appointment, his visual acuity remained
stable at light perception and IOP had increased to 10 mm Hg. A repeat B-scan
showed that the choroidal effusion had resolved but the vitreous hemorrhage
persisted.
Figure 3: Post-operative anterior segment imaging.
(A) Anterior
segment OCT and (B) Ultrasound biomicroscopy of the iridocorneal angle showing
appropriate placement of the CyPass stent (white arrow) in the supraciliary
space.
Discussion
To our knowledge, this is the first reported case of a phacoemulsification/CyPass®
stent implantation surgery being complicated by post-operative vitreous
hemorrhage in the setting of hypotony. While suprachoroidal hemorrhage have
been known to occur with intraocular surgical procedures (5), there
were no clinical findings concerning for suprachoroidal hemorrhage in our
patient. Additionally, we would expect such a hemorrhage to be limited to the
suprachoroidal space and not spill over into the vitreous cavity. A
communication between the two spaces could have been created by inaccurate
placement of the CyPass device, but appropriate placement was confirmed by
multiple methods including gonioscopy, anterior segment OCT (Figure 2A), and
ultrasound biomicroscopy (Figure 2B).
One
possible alternative mechanism that we considered was spill-over hemorrhage
from the anterior chamber hyphema. As was noted previously, the COMPASS trial
has shown that hyphema is a known complication of CyPass implantation (3).
Furthermore, pseudoexfoliation has been associated with zonular instability,
including zonular dialysis (6), which would allow for communication
between the anterior and posterior segments. We therefore posit the possibility
that a post-operative hyphema carried over into the posterior segment through
such an opening. However, the vitreous hemorrhage that we observed was dense,
causing light projection vision and likely cannot be fully explained by
spill-over hemorrhage alone.
Another
possibility is occult retinal neovascularization that was unmasked in the
setting of hypotony and manifested as hemorrhage. However, the patient’s only
risk factor prior to surgery was hypertension and pre-operative funduscopic
exam did not note any evidence of hypertensive retinopathy. In a similar vein,
alternative mechanisms for hypotony-mediated hemorrhage have been proposed. One
mechanism is a mechanically induced retinal vein occlusion caused by anterior
shifting of the lamina cribrosa and blockage of axonal transport, leading to retinal
vein compression (7,8). An additional mechanism is a hemorrhagic
posterior vitreous detachment caused by the vitreous body being suddenly pulled
forward (9,10).
Finally,
although less likely, a phenomenon known as acute ocular decompressive
retinopathy has been described. This condition is characterized by retinal
hemorrhages which can include vitreous and subhyaloid hemorrhages that occur
shortly following a rapid drop in IOP such as that associated with tube
shunt and filtering surgeries (101. This is thought to occur when a
sudden drop in IOP leads to a sudden increase in blood flow through retinal
vessels with impaired autoregulation, thereby overwhelming the normal
capacitance of these vessels (10). One review of 32 studies found
that the average IOP drop associated with this condition was 33 mm Hg but
ranged from 4-57 mm Hg. Given that the patient’s pre-operative intraocular
pressure was 15 mm Hg and dropped to as low as 4 mm Hg postoperatively, this is
certainly a consideration.
While
it is unclear what caused the dense post-operative vitreous hemorrhage observed
in our patient, it is likely related to the post-operative hypotony. Per the COMPASS
trial, hypotony was one of the more common adverse events encountered after
CyPass stent placement (3). As such, our case shows that it is
important to be prepared for the possible sequela of prolonged hypotony. The
differential diagnosis for hemorrhage triggered by hypotony is diverse, and the
various possibilities should be prioritized and investigated based using an
individualized approach that considers a patient’s unique perioperative risk
factors.
Conclusions
In summary, this case illustrates a
complication of CyPass® stent placement that had not been previously
published. There were no pre-operative findings on exam that would have
suggested this patient would have been at risk for developing a post-operative
vitreous hemorrhage. This complication was therefore most likely due to
post-operative hypotony created by stent placement or by spillover of blood
from the anterior chamber to the vitreous cavity through zonular defects
commonly seen in pseudoexfoliation. As hypotony is not an uncommon complication
after incisional glaucoma surgery, it is important to be prepared for it as
well as any associated sequela. Furthermore, while this patient did not have
pre-operative risk factors for developing vitreous hemorrhage, such as
retinopathy, it is important to conduct a thorough pre-operative examination
and be cognizant of such risks factors if they are present.
Patient Consent
As no identifying
information is disclosed, patient consent was not obtained.
Acknowledgements and Disclosures
Supported in part by the Research to Prevent
Blindness, New York, NY and Visual Sciences Core Grant EY020799.
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