Neovascular Glaucoma
- Author: Jacqueline Freudenthal, MD; Chief Editor:
Hampton Roy Sr, MD
Background
Neovascular glaucoma (NVG) is
classified as a secondary glaucoma. First documented in 1871, historically, it
has been referred to as hemorrhagic glaucoma, thrombotic glaucoma, congestive
glaucoma, rubeotic glaucoma, and diabetic hemorrhagic glaucoma. Numerous secondary
ocular and systemic diseases that share one common element, retinal
ischemia/hypoxia and subsequent release of an angiogenesis factor, cause NVG.
This angiogenesis factor causes new blood vessel growth from preexisting
vascular structure. Depending on the progression of NVG, it can cause glaucoma
either through secondary open-angle or secondary closed-angle mechanisms. This
is accomplished through the growth of a fibrovascular membrane over the
trabecular meshwork in the anterior chamber angle, resulting in obstruction of
the meshwork and/or associated peripheral anterior synechiae.
NVG is a potentially devastating
glaucoma, where delayed diagnosis or poor management can result in complete
loss of vision or, quite possibly, loss of the globe itself. Early diagnosis of
the disease, followed by immediate and aggressive treatment, is imperative. In
managing NVG, it is essential to treat both the elevated intraocular pressure
(IOP) and the underlying cause of the disease.
Pathophysiology
Retinal ischemia is the most common
and important mechanism in most, if not all, cases that result in the anterior
segment changes causing NVG. Various predisposing conditions cause retinal
hypoxia and, consequently, production of an angiogenesis factor.
Several angiogenesis factors have
been identified as potential agents causing ocular neovascularization. Recent
studies suggest that vascular endothelial growth factor (VEGF) might play a
central role in angiogenesis.
Once released, the angiogenic
factor(s) diffuses into the aqueous and the anterior segment and interacts with
vascular structures in areas where the greatest aqueous-tissue contact occurs.
The resultant growth of new vessels at the pupillary border and iris surface
(neovascularization of the iris [NVI]) and over the iris angle
(neovascularization of the angle [NVA]) ultimately leads to formation of
fibrovascular membranes. The fibrovascular membranes, which may be invisible on
gonioscopy, accompany NVA and progressively obstruct the trabecular meshwork.
This causes secondary open-angle glaucoma.
As the disease process continues,
the fibrovascular membranes along the NVA tend to mature and contract, thereby
tenting the iris toward the trabecular meshwork and resulting in peripheral
anterior synechiae and progressive synechial angle closure. Elevated IOP is a
direct result of this secondary angle-closure glaucoma.
Epidemiology
Frequency
United
States
Incidence of NVG is rare.
Mortality/Morbidity
Treatment of NVG is difficult.
Maintaining visual acuity in patients with NVG also is difficult.
Age
NVG is more prevalent in elderly
patients.
History
A careful and detailed ocular and
systemic history is imperative in diagnosing both neovascular glaucoma (NVG)
and the underlying problem causing it.
Physical
A complete ocular examination of
both eyes, particularly of the posterior segment, will almost certainly provide
the etiology of neovascularization. Of the 3 most common causes of NVG, ocular
ischemic syndrome presents as a diagnostic dilemma and, thus, deserves special
mention.
The typical clinical presentation
of NVG is the same regardless of the underlying cause. The typical clinical
presentation can be divided into the following 2 stages: the early stage and
the advanced stage. These stages generally follow each other in progression,
and the early stage is subdivided further into rubeosis iridis and secondary
open-angle glaucoma.
Early stage (rubeosis
iridis)
- Normal IOP
- Presence of
tiny, neovascular, dilated capillary tufts at pupillary margin
- High magnification
on slit lamp (to view earliest finding in NVG)
- NVI
(irregular, nonradial vessels usually not in the iris stroma)
- NVA (can
occur with or without NVI)
- Careful
gonioscopy in all eyes at high risk for NVG even without pupillary and
iris involvement
- Poorly
reactive pupil
- Ectropion
uvea
Early stage (secondary
open-angle glaucoma)
- Elevated
IOP
- NVI
continuous with NVA
- Proliferation
of neovascular tissue over the angle
- Fibrovascular
membranes (develop circumferentially across the angle, blocking the trabecular
meshwork)
Advanced stage
In this stage, secondary
angle-closure glaucoma is characterized by some or all of the following:
- Acute
severe pain, headache, nausea, and/or vomiting
- Photophobia
- Reduced
visual acuity (counting fingers to hand motion)
- Elevated
IOP (≥ 60 mm Hg)
- Conjunctival
injection
- Corneal
edema
- Plus/minus
hyphema
- Aqueous
flare
- Synechial
angle closure
- Severe
rubeosis
- Distorted,
fixed, mid-dilated pupil and ectropion uveae
- Retinal
neovascularization and/or hemorrhage
- Optic nerve
cupping (possibly)
Ocular ischemic
syndrome
Ocular ischemic syndrome occurs in
the presence of more than 90% of patients with carotid artery stenosis, but it
can occur as a result of aortic arch disease (eg, syphilis, Takayasu arteritis,
dissecting aneurysm), in which case the presentation may be bilateral.
Symptoms include a dull
periocular/periorbital pain that can be secondary to the ischemia and/or NVG.
Signs include the following:
- Vision can
vary from 20/20 to no light perception.
- Midperipheral
intraretinal hemorrhage (in contrast to diabetic retinopathy and CRVO
where the hemorrhage is mostly situated in the posterior pole)
- IOP can be
elevated secondary to NVG, decreased secondary to ciliary body
hypoperfusion, or normal as a result of both processes.
- Other signs
include corneal decompensation, iritis, iris atrophy, cataract, and
spontaneous pulsations of the central retinal artery.
- Intravenous
fluorescein angiogram will demonstrate prolonged choroidal filling and
increased arteriovenous transit time.
Causes
Relatively frequent causes of NVG
include the following:
Less frequent causes of NVG
include the following:
Imaging
Studies
- Intravenous fluorescein angiogram and
electroretinography (ERG) to assess retinal ischemia
- B-scan ultrasound
- Optical coherence tomography[2] -
Images observed per grade of neovascular glaucoma
Grades are as follows:
- Grade 1: No modification
- Grade 2: A slightly hyper-reflective linear iris
secondary to neovascularization
- Grade 3: A thickened hyper-reflective iridocorneal
angle with possible iridocorneal synechiae
- Grade 4: Closed iridocorneal angle associated with iris
contraction and uveae ectropion
Medical
Care
General principles for treating
patients with neovascular glaucoma (NVG) include the following:
- Identifying the underlying etiology is fundamental in
the management of NVG.
- CRVO, diabetic retinopathy, CAOD, and CRAO require
systemic workup and appropriate intervention to prevent further complications.
- The management of NVG is approached through the
following 4 stages that reflect the progression of the disease:
prophylactic treatment, early-stage treatment, advanced-stage treatment,
and end-stage treatment.
Prophylactic
treatment
Most patients are either at high
risk for developing NVI/NVG or have early NVI with normal IOP. Prevention of
NVG is the single most important aspect in its management.
Reducing the amount of viable retina
is known to inhibit and even to reverse new vessel proliferation in the
anterior segment. The mainstay in prevention is retinal ablation achieved via
panretinal photocoagulation (PRP) or cryophototherapy because of media
opacities (ie, corneal edema, cataract, vitreous hemorrhage) or other patient
factors. Other treatment options in this stage include goniophotocoagulation.
PRP can be delivered in the
following 3 ways: slit lamp delivery system, indirect laser, or endolaser at
time of vitrectomy.
The amount of PRP required varies.
The Diabetic Retinopathy Study (DRS) guidelines recommend 1200-1500 burns, with
a spot size of 500 µm to be applied to the peripheral retina. Many retina
specialists recommend 1500-2000 burns, with a spot size of 500-800 µm, using a
wide-angle fundus contact lens (eg, Rodenstock). The types of laser include
argon, krypton (better with media opacities and retinal hemorrhages), and diode
(same utility as krypton laser).
To begin, a 360° peritomy is
performed with isolation of the 4 recti muscles. A 2.5-mm retinal cryoprobe is
used to create cryoapplication burns just anterior to the equator. Three spots
are placed between each rectus muscle. Two additional rows of application are
performed posterior to the first so that the third row is just outside the
major vascular arcades. In total, 32 cryoapplications are performed under
direct visualization. The probe tip remains in contact with the sclera until
70° has been maintained for 5-10 seconds. This procedure causes considerable
inflammation, and complications (eg, tractional and exudative retinal
detachment, vitreous hemorrhage) can occur.
Goniophotocoagulation, another laser
therapy, is performed directly to NVI before the development of NVG. Its role
in management of NVG is unclear, and it has not proven to be beneficial in
preventing synechial closure of angle or advanced NVG.
All patients should undergo
fluorescein angiography to delineate nonischemic CRVO from ischemic CRVO.
Virtually no patients with nonischemic CRVO develop NVG. Overall incidence of
NVG is 40% for an ischemic CRVO. NVI and NVG can appear from 2 weeks to 2
years. More than 80% of patients with NVI/NVG present within the first 6
months. Of patients with nonischemic CRVO, 15% can convert to ischemic CRVO
within 8 months. The strongest predictors of NVI/NVG following CRVO include
extensive retinal capillary nonperfusion of intravenous fluorescein angiography
(IVFA), extensive retinal hemorrhages, short duration of occlusion, and male
sex. In the Central Retinal Vein Occlusion Study, PRP was indicated for IVFA
confirmed ischemic CRVO if development of 2 clock hours of NVI occurred or any
NVA was present.[3] No
benefit occurred when prophylactic PRP was performed prior to the development
of NVI or NVA when frequent follow-up care was provided.
Prophylactic PRP still is
recommended by many retinal specialists before the development of NVI or NVA,
especially in case of the following: clear extensive capillary nonperfusion,
extensive systemic vascular disease, patient who is monocular, and/or
noncompliance or poor follow-up results. Preoperative care is fundamental for
all types of cataract surgery, capsulotomy, and vitreous surgery.
For patients with diabetic
retinopathy, ensure frequent follow-up care and tight glycemic control. If
proliferative diabetic retinopathy exists, then complete PRP is recommended as
treatment.
Early-stage
treatment
This stage is characterized by the
development of a fibrovascular membrane across some or all of the angle,
obstructing the trabecular meshwork, and an increase in IOP.
With secondary open-angle glaucoma,
treatment is identical to prophylactic treatment and includes PRP (filler PRP
if already performed initially), panretinal cryotherapy, and medical therapy.
The most important medical therapy
for this stage includes topical atropine 1% to decrease ocular congestion and
topical steroids (eg, prednisolone [Pred Forte, Inflamase Forte]) to decrease
inflammation. Standard antiglaucoma medications to treat secondary open-angle
glaucoma are recommended. Other agents include topical beta-blockers (eg,
levobunolol [Betagan], timolol [Timoptic]), topical brimonidine (Alphagan),
topical carbonic anhydrase inhibitor (eg, dorzolamide [Trusopt], brinzolamide
[Azopt]), and oral carbonic anhydrase inhibitor (eg, acetazolamide [Diamox]).
Topical pilocarpine is contraindicated because it may increase inflammation.
The role of topical latanoprost (Xalatan) is unclear in the treatment of early
NVG.
The successful use of photodynamic
therapy with verteporfin directed at the iris and the angle to obliterate
neovascularization and to reduce IOP has been reported.
Advanced-stage
treatment
This stage is characterized by
synechial closure of the angle and secondary angle-closure glaucoma.
PRP is still the initial and most
important treatment, both to prevent further NVI/NVA and angle closure and to
prepare the eye for surgical intervention (see Surgical Care). Surgical
intervention is indicated in eyes with potential for useful vision.
Medical therapy is indicated, with
topical atropine and steroids being the most important agents. Antiglaucoma
medications, topical beta-blockers, and carbonic anhydrase inhibitors are also
recommended. The role of topical brimonidine and latanoprost in advanced
disease is unclear. Topical pilocarpine and echothiophate iodide are
contraindicated (may cause increased inflammation and hyperemia). Oral glycerol
and intravenous mannitol are recommended only if IOP is elevated
symptomatically.
Anti-VEGF
therapy
Antivascular endothelial growth factor is frequently used for various conditions in which VEGF
release is induced in response to retinal ischemia. It is still under study as
an adjunct[4] or
alternative treatment for NVG. Anti-VEGFs such as bevacizumab (Avastin),
pegaptanib sodium (Macugen), and ranibizumab (Lucentis) block angiogenic
factors that promote the formation of new vessels, reversing the
neovascularization process. The initial use of anti-VEGF agents for the
treatment of retinal neovascularization has been expanded to include other
pathology such as neovascular glaucoma.[5] The
quantity of growth factors in the aqueous decrease after intraocular injection
of anti-VEGFs, decreasing further progression of angular damage secondary to
IOP increments.[6] However,
other investigators have reported a lack of efficacy of intravitreal
bevacizumab in the treatment of neovascularization of theiris and iridocorneal
anglebut support its use for diabetic retinopathy and central vein occlusion.[7]
Several studies propose the use of
anti-VEGF agents with traditional treatments such as panretinal
photocoagulation (PRP), with or without additional surgery and vary in the
timing, combination, and place of injection (intracameral or intravitreal, or
both simultaneously). The most frequent recommendation by various authors for
treatment is the adjunct combination of intravitreal bevacizumab/panretinal
photocoagulation for the treatment of neovascular glaucoma (NVG) instead of PRP
alone or as alternative treatment when visibility of the posterior segment is
difficult due to opacities of the media (eg, hemorrhage).[8]
Although intravitreal, and less
commonly intracameral, delivery of anti-VEGF agents is preferred for the
management of NVG, several authors describe different protocols of treatment
according to the stage of disease and the possible underlying cause as
standardized guidelines of NVG treatment with anti-VEGFs have not yet been
established.
Several reports about the favorable
response to intravitreal anti-VEGF agents in NVG have been published. In a
review of 26 original papers between 2006 and August 2008, efficacy and safety
of the procedure in 127 eyes was analyzed in a series of cases: None had been
performed in a clinical randomized controlled assay. The efficacy calculated in
the sample was 68.7%, and the recurrence rate was 18.6% at 4.2 months of
follow-up. Ophthalmic complications were under 0.78%, and no systemic
complications were found.[9]
Intravitreal bevacizumab is the most
frequent anti-VEGF adjunct treatment used for NVG due to the lower cost.
Systematic review of the efficacy and safety of intravitreal bevacizumab (IVB)
in the treatment of neovascular glaucoma (NVG) establishes bevacizumab is well
tolerated, effectively stabilizes INV activity, and controls IOP in patients
with INV when used alone and at an early-stage of NVG.[10]
Randomized clinical trials are now
being reported. Intraocular doses described for treatment with bevacizumab are
1 mg/0.05 mL, 1.25 mg/0.05 mL, or 2.5 mg/0.05 mL, according to the stage and
recurrence of NVG.
In a case of ocular ischemic
syndrome, a single injection of intravitreal bevacizumab (1.25 mg/0.05 mL
injection) detained all signs of neovascularization just one day after
injection but failed to control IOP.[11]
Postintravitreal injection of a
single dose of bevacizumab (1.25 mg) promotes quick response of pain relief 1
week postinjection;[12]
this safely facilitates further surgical intervention to lower IOP
when treating refractory NVG.
End-stage
treatment
This stage is characterized by
complete angle closure by peripheral anterior synechiae with no remaining
useful vision.
The primary goal of treatment in
this stage is pain control. Medical therapy includes topical atropine 1% and
steroids. If corneal decompensation occurs, use a bandage contact lens.
Cyclodestructive procedures are performed if medical therapy fails to provide
symptomatic relief. With cyclocryotherapy, the IOP-lowering effect is achieved
by destroying secretory ciliary epithelium and/or reducing blood flow to the
ciliary body. It is indicated as a last resort only if relief of pain is the
main goal. In a large series, 34% of eyes achieved IOP of less than 25 mm Hg;
however, 34% of eyes became phthisical and 57% of eyes lost all light
perception. Other complications include sympathetic ophthalmia and anterior
segment ischemia.
With Nd:YAG laser transscleral
cyclophotocoagulation, 2 approaches, contact and noncontact, are used. In the
contact approach, one study reported a 40% decrease in IOP to less than 19 mm
Hg in eyes with NVG. In the noncontact approach, out of 27 eyes with NVG, only
15% achieved satisfactory IOP control.
The results of diode laser
transscleral cyclophotocoagulation are similar to Nd:YAG cyclophotocoagulation.
Direct laser cyclophotocoagulation
is performed under direct observation using the argon laser. Two approaches,
transpupil or with endoscopy, are used. Its role in NVG management is
secondary. Success in controlling IOP is limited (may have less inflammation
and pain versus cyclocryotherapy).
Retrobulbar alcohol injection is
indicated after all medical and surgical options have been explored and the
patient does not want an enucleation. Complications include external
ophthalmoplegia and blepharoptosis. Enucleation is indicated only if
intractable pain is not relieved by any other treatment modality.
Surgical
Care
Surgical care is indicated in
patients with remaining useful vision. Preoperative care is fundamental to the
postoperative success of any surgical intervention.
- With surgical care, ensure that adequate PRP is
completed to reduce vasoproliferative stimulus. Atropine and steroids are
indicated to decrease inflammation, and antiglaucoma medication is
indicated to decrease IOP. Wait approximately 3-4 weeks to allow the eye
to quiet down.
- Surgical modalities include trabeculectomy with or
without an antifibrotic agent and valve implant surgery.
- Trabeculectomy with the antifibrotic agents
mitomycin-C and 5-fluorouracil (5-FU) is one modality. Trabeculectomy in
NVG has a significant failure rate. Using standard trabeculectomy
(without antifibrosis), an IOP of less than 25 mm Hg on one medication or
less has been reported to occur in 67-100% of patients in 3 studies.
Using injections of 5-FU subconjunctivally in the postoperative period,
the surgical success has been reported to be 68% over 3 years. Inject 0.1
mL of 5 mg/mL 5-FU subconjunctivally either superiorly above the bleb or
inferiorly (just above the lower fornix). Mitomycin-C used
intraoperatively has been shown to be more effective than 5-FU in routine
trabeculectomies. No significant follow-up studies exist on the use of
mitomycin-C with trabeculectomy in NVG.
- A retrospective cohort study from January 1994 to
March 2007 of 101 eyes found that the prognostic factors for failure of
trabeculectomy with MMC for NVG were younger age and previous vitrectomy
in patients with NVG, having a fellow eye with NVG in patients with
disease caused by diabetic retinopathy, and persistent proliferative
membrane and/or retinal detachment after vitrectomy.[13]
- Valve implant surgery is another modality and is
indicated when trabeculectomy fails or extensive conjunctival scarring
exists, thereby preventing a standard filtering procedure. Molteno,
Krupin, and Ahmed valve implants commonly are used. One large series
using the Krupin valve reported 79% of eyes with NVG had a 67% success
rate in controlling IOP (< 24 mm Hg) with mean follow-up of 23 months.
Long-term results are mixed. Using the Molteno implant, 60 eyes with NVG
achieved a satisfactory IOP (< 21 mm Hg) and maintenance of visual
acuity over 5 years of only 10.3%. If combined with the need for
vitrectomy, consideration of pars plana tube-shunt insertion may reduce
anterior segment complications.
- Complications include postoperative hypotony with
associated complications, blockage of internal fistula, blockage of
external filtration site (fibrosis of the filtering bleb), and corneal
endothelial loss.
- Adjunct anti-VEGF therapy
- In a short case series, the use of intracamerular
bevacizumab prior to trabeculectomy with MMC improved NVG.[14]
- The postoperative inhibition of angiogenesis after
glaucoma surgery has also been described. Possible routes of bevacizumab
administration are subconjunctival application during trabeculectomy,
postoperative needling, or intravitreal injection during a filtrating
procedure.[15]
- Bevacizumab has also been injected into the silicone
oil in eyes with neovascular glaucoma after vitrectomy for advanced
diabetic retinopathy with favorable outcomes.[16]
- Intravitreal bevacizumab is useful to safely and
effectively implant an aqueous shunting tube in eyes with severe NVG and
intractable IOP, in addition to postoperative panretinal photocoagulation
that reduces the recurrence of neovascular activity improving the success
rate of aqueous shunting surgery.[17]
·
Medication Summary
·
The most important medications include a regimen
of topical steroids and atropine. Antiglaucoma medications include both topical
and oral agents.
·
Cycloplegic drugs
·
Class Summary
·
Paralyze ciliary muscle, preventing ciliary
muscle spasm; provide pain relief; and decrease ocular congestion.
·
·
Acts at parasympathetic sites in smooth muscle to
block response of sphincter muscle of iris and muscle of ciliary body to
acetylcholine, causing mydriasis and cycloplegia.
·
Steroidal anti-inflammatory
·
Class Summary
·
Decreases ocular inflammation.
·
·
Treats acute inflammations following eye surgery
or other types of insults to eye. Decreases inflammation and corneal
neovascularization. Suppresses migration of polymorphonuclear leukocytes and
reverses increased capillary permeability. In cases of bacterial infections,
concomitant use of anti-infective agents is mandatory; if signs and symptoms do
not improve after 2 days, reevaluate patient. Dosing may be reduced, but advise
patients not to discontinue therapy prematurely.
·
Alpha2-adrenergic agonists
·
Class Summary
·
Decrease IOP by reducing aqueous humor
production.
·
·
Selective alpha2-receptor that reduces aqueous
humor formation.
·
Carbonic anhydrase inhibitors
·
Class Summary
·
By slowing the formation of bicarbonate ions
with subsequent reduction in sodium and fluid transport, it may inhibit
carbonic anhydrase in the ciliary processes of the eye. This effect decreases
aqueous humor secretion, reducing IOP.
·
·
Used concomitantly with other topical ophthalmic
drug products to lower IOP. If more than one ophthalmic drug is being used,
administer drugs at least 10 min apart. Reversibly inhibits carbonic anhydrase,
reducing hydrogen ion secretion at renal tubule and increasing renal excretion
of sodium, potassium bicarbonate, and water to decrease production of aqueous
humor.
·
·
Inhibits enzyme carbonic anhydrase, reducing
rate of aqueous humor formation, which, in turn, reduces IOP. Used for
adjunctive treatment of chronic simple (open-angle) glaucoma and secondary
glaucoma and preoperatively in acute angle-closure glaucoma when delay of
surgery desired to lower IOP.
·
Prostaglandins
·
Class Summary
·
Used to reduce IOP in patients who are
intolerant or resistant to other IOP-lowering medications. They are
contraindicated in glaucomas in which inflammation is a prominent ocular
finding.
·
·
Prostaglandin analog that selectively mimics
effects of naturally occurring substances, prostamides. Exact mechanism of
action unknown but believed to reduce IOP by increasing outflow of aqueous
humor through trabecular meshwork and uveoscleral routes.
·
·
Prostaglandin F2-alpha analog and selective FP
prostanoid receptor agonist. Exact mechanism of action unknown but believed to
reduce IOP by increasing uveoscleral outflow.
·
·
Prostaglandin F2-alpha analog and selective FP
prostanoid receptor agonist. Exact mechanism of action unknown but believed to
reduce IOP by increasing uveoscleral outflow and facilitating conventional
outflow through the trabecular meshwork
·
Beta-adrenergic blockers
·
Class Summary
·
The exact mechanism of ocular antihypertensive
action is not established, but it appears to be a reduction of aqueous humor
production.
·
·
Nonselective beta-adrenergic blocking agent that
lowers IOP by reducing aqueous humor production.
·
·
May reduce elevated and normal IOP, with or
without glaucoma, by reducing production of aqueous humor.
Further
Outpatient Care
- Ophthalmologists should provide long-term follow-up
care for patients with neovascular glaucoma (NVG), closely monitoring for
any worsening in the patient's condition.
- Intensity of follow-up care is related to the
conditions predisposing the patient to the development of NVG (ie, CRVO,
diabetic retinopathy).
Complications
- Complications include uncontrolled glaucoma, hyphema,
and loss of vision.
Prognosis
- Generally, NVG carries a very guarded prognosis.
Prognosis is highly dependent on the following 2 factors: prevention and
treatment of NVG early in its course and the underlying disease process.
Patient
Education