Neovascular glaucoma

A careful and detailed ocular and systemic history is imperative in diagnosing neovascular glaucoma and the underlying problem causing it.

The primary condition affects the vision (most often proliferative diabetic retinopathy or ischaemic central retinal vein occlusion). In a more advanced stage, the NVG itself further affects the vision and is most often at the level of counting fingers to hand motions only. A painless, sudden decrease in vision 60-90 days before presentation is typical of CRVO-related NVG.

Patients who developed a later stage of neovascular glaucoma, often have severe eye pain, redness, and decreased vision. Some patients may vomit. Remember that patients with angle closure or pupillary block have similar symptoms . However, in those patients, you will not see the presence of new vessels of the iris or angle.

The clinical presentation of neovascular glaucoma is the same – regardless of the underlying condition. The very early stage, which manifests with normal intraocular pressure (IOP), represents new vessels of the iris. You will see the following clinical findings, according to the stage of the disease (6,7):

Early stage (rubeosis of the iris)

• Normal IOP
• Presence of tiny, neovascular, dilated capillary tufts at the pupillary margin (use high magnification on slit lamp)
• New vessels of the iris (NVI) – irregular, nonradial vessels usually not in the iris stroma
• New vessels of the angle (NVA) – can occur with or without NVI
• Poorly reactive pupil
• Ectropion uvea (the presence of iris pigment epithelium on the anterior surface of the iris)

Careful gonioscopy is essential in all high-risk cases of NVG, even when pupillary margin and iris are not involved.

Early stage (secondary open-angle glaucoma)

• Elevated IOP
• NVI continuous with NVA
• The proliferation of neovascular tissue over the angle

Fibrovascular membranes (develop circumferentially across the angle, blocking the trabecular meshwork)

Advanced stage (secondary closed-angle glaucoma)
Patients have some or all of the below signs:

• 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 oedema
• Plus/minus hyphema
• Aqueous flare
• Synechial angle closure
• Severe rubeosis
• Distorted, fixed, mid-dilated pupil and ectropion uvea
• Retinal neovascularisation and/or haemorrhage

Diagnosis of neovascular glaucoma is based on clinical presentation.

Gonioscopy – by using a special lens, you can examine the iridocorneal angle. In the case of neovascular glaucoma, you can observe the angle of new vessels and fibrotic membranes. It is a crucial diagnostic procedure in the early phase of the condition. All patients with proliferative diabetic retinopathy, ischaemic central retinal vein occlusion, and ischaemic ocular syndrome should have gonioscopy at baseline.

Colour fundus photography – it is important to find the underlying condition and retinal ischemia. In many cases of neovascular glaucoma, new vessels of the retina or optic disc are present.

OCT angiography is a novel and non-invasive tool that is very helpful in confirming retinal ischemia. Confirmation of retinal ischaemia does not mean the patient has or will develop neovascular glaucoma. Nonetheless, they will have a higher risk of developing it, depending on the underlying condition.

Identifying the underlying aetiology is fundamental in the management of neovascular glaucoma. Patients with diabetic retinopathy, ischaemic ocular syndrome, retinal vein, and artery occlusions need systemic workups.

In patients whose retinal ischaemia is the underlying cause of neovascular glaucoma, pan-retinal photocoagulation laser (PRP laser) is essential in treatment. The laser treatment reduces the stimulus for new vessels of anterior segments (VEGF factor). Nowadays, intravitreal anti-VEGF agents play a significant role in managing patients with neovascular glaucoma. The duration of suppression of the iris and angle neovascularisation lasts approximately 3-6 weeks with anti-VEGF injections, thereby creating a window of opportunity to allow adequate PRP and/or glaucoma surgery to be carried out.(8,9) It is important to highlight the prophylactic effect of PRP laser in cases with severe retinal ischaemia and no signs of NVG.

Medical treatment in the early stage of the disease includes topical Atropine 1%, which decreases congestion. Then, local steroids have a role in reducing inflammation (short course).Finally, topical anti-glaucoma agents reduce intraocular pressure. Recommeded agents are topical beta-blockers, brimonidine, and carbonic anhydrase inhibitors. Oral carbonic anhydrase inhibitors (Diamox) also have a role in regulating intraocular pressure.

The advanced stage of the disease requires a surgical approach. Pan-retinal photocoagulation laser still has an important role, and the above medical treatment is recommended. In eyes with vision better than 20/400, most glaucoma specialists prefer glaucoma drainage implant placement or filtering surgery versus cyclophotocoagulation.(10,11)