TRABECULECTOMY COMPLICATIONS
(PART 1)
PRE-OPERATIVE CONSIDERATIONS:
- Stop topical cholinesterase inhibitors (e.g.
phospholine iodide) 2-3 weeks before surgery in order to reduce the chances of
hyphema and postoperative uveitis.
- Topical epinephrine products should be stopped 3
days before surgery.
- Miotics break down the blood-aqueous barrier and should be stopped 2 weeks preoperatively.
- Steroids: Topical steroids can be started prior to surgery (1-3 weeks before op: Barneby) (2-7
days preop: Pearls of glaucoma management). Oral steroids in
appropriate doses can be started in patients with high risk of failure due to
inflammation e.g. uveitic-glaucoma.
INTRA-OPERATIVE CONSIDERATIONS:
·
Limbus-based conjunctival flap:
o
Inadvertent injury to extra-ocular muscles and
anterior ciliary vessels may occur.
o
Excessive conjunctival manipulation can produce
button-holes, thin blebs and lead to scarring.
·
Fornix-based conjunctival flap:
o
There can be difficulty in locating posterior
sources of bleeding.
o
There can be increased possibility of aqueous
leakage at the limbus (especially if adjunctive anti-metabolites are used)
·
Scleral flap:
o
Be aware of the abrupt change in the curvature
of the globe at the limbus to avoid premature entry into the anterior chamber (AC).
o
It is important to maintain a uniform scleral
flap thickness.
o
If the lateral edges of the scleral flap are
‘feathered”, excessive aqueous may leak through poorly apposed wound edges postoperatively.
o
A very thin scleral flap can result in
dehiscence, maceration or avulsion during manipulation and suturing. The torn
scleral flap can be sutured with 10-0 or 11-0 nylon sutures on a non-cutting
needle. A plug of Tenon’s capsule can be sutured to close a scleral buttonhole.
If required, a donor scleral or autologous (dura mater or pericardium) graft
can be used to close a buttonhole or a new flap needs to be constructed after
closing the defect.
·
Conjunctival buttonholes:
o
These can be avoided by limiting dissection with
sharp instruments. If a large buttonhole is created early during the procedure,
choose a different site for surgery.
o
A 10-0 or 11-0 nylon/polyglactin suture on a
non-cutting vascular needle can be used to close the conjunctiva in a
shoestring or mattress fashion. Tenon’s capsule can be incorporated into the
defect. If the buttonhole is near the limbus the conjunctiva with the hole can
be excised, the cornea abraded lightly with a blade and the conjunctiva sutured
to the area by 10-0 nylon mattress sutures. A buttonhole noted near the end of
the surgery can be closed by an autologous conjunctiva graft from the inferior
conjunctiva. Amniotic membrane transplantation is also possible.
·
Hemorrhage:
o
Episcleral bleeding is common, especially those
on long-term antiglaucoma medications. Some suggest stopping the topical
treatment and putting the patient on Oral Acetazolamide a few days prior to
surgery. Damage to the ciliary body can also cause brisk bleeding. Cautery may
not work, but intraocular bipolar units on a low setting may be effective.
Alternatively, sustained, gentle pressure with a sponge on the fistula or an
air bubble in the AC may be attempted. Choroidal/expulsive hemorrhage can
result from sudden decompression causing rupture of a choroidal vessel. An
immediate inferior temporal scleral incision is practiced by some.
·
Choroidal effusion:
o
It can occur in patients with prominent
episcleral vessels, e.g. Sturge-Weber Syndrome. It is characterized by sudden
shallowing of AC or rotation of ciliary processes through the iridectomy into
the sclerostomy. It is managed by making a scleral incision to release
suprachoroidal pressure.
·
Other complications:
o
Vitreous
loss during creation of fistula or iridectomy, due to rupture of lens
zonules and hyaloid membrane due to excessive manipulation. It can be managed
by vitrectomy (manual or automated). Lens
injury and stripping of Descemet’s
membrane may occur.
·
Intra-operative suture manipulation to
control intra-ocular pressure (IOP):
o
Releasable scleral flap sutures can be applied
to prevent sudden lowering of IOP (hypotony) in the postoperative period. The
sutures can be removed 1-14 days after surgery.
o
Passage of a needle during suturing can cause
intraoperative laceration or disinsertion (amputation) of the scleral flap.
Injury to the lens, corneal endothelium or intra-ocular hemorrhage can occur if
the needle is misdirected. Scleral flap disinsertion can be avoided by making
the flap of atleast 1/3rd scleral thickness. Avoid exposed suture
ends or knots as they cause ocular irritation and act as a wick leading to
blebitis or endophthalmitis.
o
Scleral flap sutures can also be lysed postoperatively by Argon
laser. A topical anesthetic and phenylephrine to constrict the conjunctival vessels
can be applied. A Hoskins, Zeiss or Ritch lens can be used. The laser settings
are: 50µ spot size, 0.1 second duration and power between 200-600 mW. It may
occasionally be difficult to identify the suture due to overlying fibrosis,
edema or hemorrhage. Excessive manipulation of the contact lens during laser
suturelysis can cause conjunctival damage and buttonholes.
EARLY POST-OPERATIVE COMPLICATIONS:
(Occur within 4 weeks after surgery)
·
Hyphema:
o
Small intra-operative hyphemas usually resolve
within 24-48 hours and rarely require surgical intervention (AC washouts).
·
Iridocyclitis:
o
Postoperative uveitis is a common occurrence.
Corticosteroids and possibly cycloplegic agents should be given to avoid
formation of posterior synechiae and occlusion of sclerostomy site.
·
Elevated IOP with deep AC:
o
High IOP with a shallow or flat bleb and deep AC
in the early postoperative period suggests internal blockage of the sclerostomy
or tight scleral flap sutures. Immediate gonioscopy should be done (using a
lens with a diameter smaller than cornea, e.g. Zeiss). The sclerostomy can be
blocked by: incompletely excised Descemet’s membrane, iris, ciliary processes,
ciliary body, lens, lens capsule, fibrin, and vitreous or coagulated blood.
Retained viscoelastic, when used to form the AC, may also temporarily raise the
IOP. Blood and fibrin clots may also cause occlusion of the sclerostomy but
usually resolve with time and ocular massage. Tissue plasminogen activator
(TPA) can be used (5-10µ) for intracameral injection to help early lysis of the
clot. Entrapped tissue (iris, ciliary processes, lens capsule) can be disrupted
with argon or Nd:YAG laser.
o
If the internal ostium is found to be free of
obstruction, flap manipulation is required. This can be done by digital massage
or pressure to the edge of the scleral flap by a cotton tipped applicator
(cotton-bud). The scleral flap sutures should not be removed for the first 2-3
days to avoid over-filtration, hypotony, maculopathy or choroidal detachment
among others.
·
Low IOP and shallow AC:
o
Causes are: over-filtration, wound leak, aqueous
hyposecretion (temporary ciliary shutdown can occur due to over-cautery) and/or
choroidal effusion. Low IOP with shallow AC is common in early postoperative
period. The AC is shallowest on day 2-3 and gradually deepens over the next 2
weeks.
o
Postoperative AC depth is graded as follows:
GRADE
|
FEATURES
|
|
Grade 1
|
Peripheral iris-cornea touch
|
Usually AC forms simultaneously.
|
Grade 2
|
Iris sphincter-cornea touch
|
Requires conservative measures such as bed rest,
cycloplegia, pressure patch, Simmons shell/symblepharon ring/oversized
contact lens placement.
|
Grade 3
|
Lens-cornea or vitreous-cornea touch
|
A prolonged (1-2 weeks) Grade 3 AC requires
surgical intervention to prevent corneal endothelial cell loss and
decompensation, cataract, anterior/posterior synechiae and bleb failure.
Viscoelastic injection into the AC can be done as a temporary measure to wait
for the spontaneous resolution of the condition.
|
·
Aqueous hyposecretion=
Causes are: Iridocyclitis, ciliary body
detachment, cyclodialysis cleft, postoperative use of topical aqueous
suppressants in the operated eye, systemic carbonic anhydarse inhibitors,
excessive use of postoperative topical phenylephrine, ciliary body exhaustion
from an excessively large sclerostomy or leaking conjunctival wound. This leads
to a shallow or flat bleb.
·
Low IOP and deep AC:
o
A low IOP is common in the first week or two
after surgery.
·
Over-filtration:
o
It is characterized by an exuberant bleb. Such a
bleb can be avoided by releasable sutures. The condition is initially managed
by external tamponade (torpedo bandage). Gentamycin eyedrops may help by
producing some amount of scarring. Solcoceryl gel may also help. Prolonged
overfiltration may require surgically tightening of the scleral flap.
·
Wound leak:
o
Common in the early postoperative period and
characterized by a positive Seidel’s test. Non-invasive treatments include:
pressure patch, topical antibiotic, aqueous suppressants, Simmon shell or large
contact lens. Definitive therapy is surgical closure.
·
Choroidal effusion:
o
Can cause a persistently low IOP and flat AC.
This may resolve within 1-2 weeks spontaneously. A persistent flat AC or
choroidal hemorrhage requires surgical management. The AC is entered through
the old/new paracentesis. An AC maintainer is preferably inserted. Fluid is
drained from the inferior temporal quadrant. If the suprachoroidal fluid is
excessive, a scleral incision in the same quadrant is required. If eye remains
soft or AC doesn’t form, a conjunctival buttonhole should be looked for. The
scleral flap should also be tightened by additional sutures. The scleral
incision is not sutured and only the overlying conjunctiva is closed with a
running absorbable suture.
·
High IOP with shallow AC:
o
This situation may result from:
Pupillary block
|
Ciliary block (“malignant glaucoma”)
|
Suprachoroidal hemorrhage
|
Ø Pupillary
block is rare in presence of a patent peripheral iridectomy.
Ø Malignant
glaucoma (MG) =
o
There is posterior pooling of aqueous within or
behind the vitreous. It causes forward movement of the lens-iris or
hyaloid-iris diaphragm. The AC is very shallow uniformly or flat. IOP is
usually high, unless there is a choroidal detachment and/or functioning
filtration bleb. Ultrasound biomicroscopy can show fluid in suprachoroidal
space. B-scan will show fluid-filled pockets in vitreous. Risk factors for MG
include: Patients with chronic angle closure glaucoma, peripheral anterior
synechiae and uncontrolled glaucoma. It
may occur immediately following surgery or after cycloplegic agents are
discontinued. If MG occurs in one eye, there is a high risk of the condition
developing in the other eye.
o
Management of MG= Initial management is with
topical Atropine 1% (or Scopolamine 0.25%) every 6 hours, topical 2.5%
phenylephrine every 6 hours, topical and/or systemic aqueous suppressants and
systemic hyperosmotic agents. Nearly 50% of the cases resolve with medical
treatment. However, the patients may require cycloplegic therapy for the
remainder of their lives.
o
If AC doesn’t form in 3-5 days, further
treatment is required. Argon treatment of visible ciliary processes, Nd:YAG
anterior hyaloidectomy or posterior capsulotomy in aphakic/pseudophakic eyes is performed.
In case above measures fail, then surgical intervention in the form of
vitrectomy with rupture of anterior hyaloid face in apahkic/psuedophakic eyes
combined with lensectomy in phakic eyes is sufficient.
Ø
Suprachoroidal hemorrhage= It can occur
intraoperatively or in the first few postoperative days. It is characterized
by: pain, a firm eye, shallow AC and a dark mass visible in the pupil. It is
commoner in: old patients with systemic vascular disease and eyes with advanced
glaucoma, high pre-operative IOP, aphakia/pseudophakia and eyes which have
undergone previous surgical procedures including vitrectomy. Reduction of IOP
and control of hypertension prior to surgery may prevent the occurrence of a
suprachoroidal hemorrhage.
·
Loss of central fixation:
o
Early postoperative sudden loss of vision may
occur in advanced glaucoma (“snuff-out” or “wipe-out” syndrome).
o
Incidence: <0.5%
o
Patients with extensive glaucomatous damage, a
remaining small (≤5 degrees) central island of vision or VF splitting fixation
are most susceptible. This wipe out occurs with medical therapy also with equal
frequency, so surgical treatment is not a contraindication for surgery.
o
Other causes of visual deterioration include:
cystoid macula edema, hyptonic maculopathy, choroidal folds, retinal vascular
occlusion and anterior ischemic neuropathy.
·
Retinal complications:
o
Sudden lowering of IOP leads to decompression
retinopathy consisting of intraretinal, subretinal and occasional
suprachoroidal hemorrhages. Dot and blot hemorrhages mimicking CRVO are present
in mid-periphery. Prognosis for visual recovery is usually good. Early
postoperative non-rhegmatogenous serous retinal detachment can occur in
hypotonous eyes with choroidal detachment. This resolves with normalization of
IOP. Persistent surface-wrinkling maculopathy and tears in the retinal pigment
epithelium have been reported.
·
· Postoperative Endophthalmitis (POE):
o
Early POE is very rare (o.1%).
