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Neovascular Glaucoma | Ricardo Side

Wednesday, May 8, 2013



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.
·         View full drug information

·         Atropine ophthalmic (Isopto, Atropair, Atropisol)

·          
·         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.
·         View full drug information

·         Prednisolone acetate 1% (Pred Forte)

·          
·         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.
·         View full drug information

·         Brimonidine (Alphagan)

·          
·         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.
·         View full drug information

·         Dorzolamide hydrochloride 2.0% (Trusopt)

·          
·         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.
·         View full drug information

·         Acetazolamide (Diamox, Diamox Sequels)

·          
·         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.
·         View full drug information

·         Bimatoprost (Lumigan)

·          
·         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.
·         View full drug information

·         Travoprost ophthalmic solution (Travatan)

·          
·         Prostaglandin F2-alpha analog and selective FP prostanoid receptor agonist. Exact mechanism of action unknown but believed to reduce IOP by increasing uveoscleral outflow.
·         View full drug information

·         Unoprostone ophthalmic solution (Rescula)

·          
·         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.
·         View full drug information

·         Levobunolol (AKBeta, Betagan)

·          
·         Nonselective beta-adrenergic blocking agent that lowers IOP by reducing aqueous humor production.
·         View full drug information

·         Timolol maleate 0.5% (Timoptic, Timoptic XE, Blocadren)

·          
·         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


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