Neovascular Glaucoma

Overview

Neovascular glaucoma (NVG) is a severe, vision-threatening secondary glaucoma caused by pathologic neovascularization of the iris (rubeosis iridis) and anterior chamber angle, most commonly arising secondary to ischemic retinal disease.¹ Despite advances in retinal imaging and anti-VEGF therapy, NVG remains difficult to manage and is associated with high rates of vision loss, ocular morbidity, and surgical failure.¹

Epidemiology & Risk Factors

The most common causes of NVG are proliferative diabetic retinopathy, central retinal vein occlusion (particularly ischemic CRVO), and ocular ischemic syndrome from severe carotid artery disease; central retinal artery occlusion and chronic retinal detachment are less common but recognized causes. Any condition producing widespread retinal capillary non-perfusion and ischemia can potentially lead to NVG.

Pathophysiology

NVG originates from retinal ischemia, which elevates intraocular vascular endothelial growth factor (VEGF) and other proangiogenic and inflammatory mediators, inducing rubeosis iridis and fibrovascular membrane formation at the angle.¹ In diabetic retinopathy specifically, hyperglycemia-induced capillary occlusion causes retinal hypoxia, which stabilizes hypoxia-inducible factor-1α (HIF-1α) and upregulates VEGF-A and placental growth factor (PlGF), driving abnormal angiogenesis in the retina, iris, and anterior chamber angle; downregulation of endogenous inhibitors such as pigment epithelium-derived factor (PEDF) may further exacerbate this process.² Concomitant inflammation (interleukin-6, tumor necrosis factor-α) followed by transforming growth factor-β-driven fibrotic angle closure collectively produces refractory IOP elevation and optic nerve damage.² This progression — from early neovascularization with an open, functioning angle to fibrovascular membrane contraction causing angle closure — defines the clinical staging of the disease.

Clinical Presentation

Early NVG may be asymptomatic or minimally symptomatic, with rubeosis iridis noted incidentally on slit-lamp exam. As angle involvement progresses, patients develop pain (often severe, from acutely elevated IOP), redness, photophobia, and decreased vision. Advanced, poorly controlled NVG can progress to a chronically painful, blind eye.

Exam Findings

Clinical staging ranges from early to advanced disease¹:

• Early: fine, tufted new vessels at the pupillary margin (rubeosis iridis), normal IOP, open angle on gonioscopy
• Intermediate: neovascularization extends into the anterior chamber angle, IOP may begin rising as the angle is compromised
• Advanced: fibrovascular membrane contraction causes progressive synechial angle closure, producing markedly elevated, often refractory IOP; conjunctival injection, corneal edema, and significant pain are common
• End-stage: total angle closure, severely elevated IOP, and a painful, often blind eye

Differential Diagnosis

• Uveitic glaucoma with iris vessel dilation (can mimic mild rubeosis but lacks true neovascular membrane)
• Iridocorneal endothelial (ICE) syndrome
• Angle-recession glaucoma from prior trauma
• Other causes of acute angle closure (primary angle-closure glaucoma) — distinguished by the absence of neovascularization

Management

Diagnosis requires careful slit-lamp examination and gonioscopy to detect early rubeosis and angle neovascularization, supplemented by multimodal imaging: ultrawidefield fluorescein angiography to quantify retinal nonperfusion, and anterior-segment OCT or ultrasound biomicroscopy to delineate fibrovascular membrane extent and angle architecture (anterior-segment OCT angiography remains investigational for this purpose).¹

Management relies on two parallel goals: rapid suppression of anterior segment neovascularization and definitive treatment of the underlying retinal ischemia.¹ Intravitreal anti-VEGF injections rapidly regress neovascularization and improve surgical conditions but are only temporizing unless combined with panretinal photocoagulation (PRP) or other ischemia-directed therapy to address the underlying driver.¹ Current anti-VEGF monotherapy is also limited by its inability to control the fibrosis and inflammation components of the disease, highlighting the need for multifaceted strategies incorporating anti-inflammatory and antifibrotic agents in more advanced or refractory cases.²

Surgical management (glaucoma drainage device implantation is generally preferred over trabeculectomy in NVG given the friable, neovascular tissue and higher failure/complication risk with trabeculectomy in this setting) is often needed once synechial angle closure has occurred, ideally after anti-VEGF pretreatment to reduce intraoperative bleeding risk. Anti-VEGF therapy, while generally safe, carries recognized systemic (cardiovascular, blood pressure, renal effects in patients with preexisting vascular risk factors) and ocular (sterile intraocular inflammation, IOP elevation, retinal detachment/tear, vascular occlusion) adverse effects that should be considered, particularly with repeated dosing.³

Complications

• Refractory, severely elevated IOP from progressive synechial angle closure
• Chronic pain and, in end-stage disease, a blind and painful eye sometimes requiring cyclodestructive procedures or enucleation for comfort
• Surgical failure is more common than in other glaucoma types, given the friable neovascular tissue and ongoing inflammatory/fibrotic drive
• Adverse effects from repeated anti-VEGF dosing, including transient or sustained IOP elevation and rare but serious ocular/systemic events³

Clinical Pearls

• Always perform gonioscopy (gently, given angle neovascularization) in any patient with risk factors for retinal ischemia and unexplained ocular findings — early rubeosis can be subtle and easily missed without careful slit-lamp and angle examination
• Anti-VEGF injection is temporizing, not curative — it must be paired with definitive treatment of the underlying retinal ischemia (typically PRP) to prevent recurrence¹
• Glaucoma drainage devices are generally preferred over trabeculectomy in NVG given the friable, neovascular tissue involved
• Anti-VEGF pretreatment before glaucoma surgery can reduce intraoperative bleeding from friable neovascular tissue
• Consider ocular ischemic syndrome (carotid disease) in a patient with NVG and no obvious retinal vascular cause — this systemic workup can be vision- and life-saving

Common Pitfalls

• Treating anti-VEGF injection as a definitive, one-time treatment rather than a bridge to definitive ischemia-directed therapy
• Missing early rubeosis iridis because gonioscopy was not performed or the exam focused only on the posterior segment
• Choosing trabeculectomy over a glaucoma drainage device in active NVG without considering the higher failure risk from friable, bleeding-prone tissue
• Overlooking systemic risk factors (uncontrolled diabetes, carotid disease) that, if addressed, could prevent NVG recurrence or fellow-eye involvement
• Underestimating the adverse effect profile of repeated anti-VEGF dosing, particularly in patients with preexisting cardiovascular or renal risk factors