Neovascular Glaucoma

Neovascular glaucoma (NVG) is a severe secondary glaucoma caused by fibrovascular membrane growth across the iris surface (rubeosis iridis) and anterior chamber angle, driven by vascular endothelial growth factor (VEGF) released from ischaemic retina, which blocks outflow and later contracts to cause angle closure.

• Causes (about 97 percent are retinal ischaemic disease): proliferative diabetic retinopathy (about one third), ischaemic central retinal vein occlusion (about one third, rubeosis in 16 to 60 percent), ocular ischaemic syndrome (carotid stenosis), long standing retinal detachment, intraocular tumours (uveal melanoma, retinoblastoma), chronic uveitis, sickle cell retinopathy, Coats disease, and after central retinal artery occlusion.
• Stages: rubeosis iridis with normal pressure, open angle (secondary open angle glaucoma) with fibrovascular membrane, then closed angle with peripheral anterior synechiae and very high pressure.

• Severe pain, redness, reduced vision, photophobia, headache, corneal oedema, with intraocular pressure often 40 to 70 mmHg.
• Fine tufts of new vessels at the pupil margin, then radiating across the iris with ectropion uveae (iris pigment epithelium turned out), a fixed pupil, hyphaema.
• Gonioscopy: vessels crossing the scleral spur and angle, membrane, then synechial closure.
• Dilated fundus: signs of ischaemia (retinal haemorrhages, cotton wool spots, neovascularisation of the disc or elsewhere) or retinal vein or artery occlusion.

• Undilated slit lamp examination of the pupil margin and iris, undilated gonioscopy (before dilating, because dilatation obscures early rubeosis and may precipitate closure).
• Tonometry, then dilated fundus assessment, fluorescein angiography (widefield) to define ischaemic area, and OCT.
• Systemic workup: blood pressure, glucose and HbA1c, lipids, carotid duplex ultrasound (ocular ischaemic syndrome), echocardiogram, and screening for vascular risk factors; B-scan if the view is poor (tumour, detachment).
• Early detection of rubeosis in patients at risk (ischaemic central retinal vein occlusion, proliferative diabetic retinopathy): examine monthly for 6 months.

• Three goals: treat the ischaemic retina (reduce VEGF), lower pressure, and control pain.
• Anti-VEGF therapy: intravitreal bevacizumab 1.25 mg in 0.05 mL (or ranibizumab 0.5 mg, aflibercept 2 mg) at diagnosis, repeated every 4 weeks as needed; regression of new vessels occurs within days, and angle opening is possible if synechiae are not established. It is an adjunct and must be combined with definitive ablation.
• Panretinal photocoagulation (1200 to 1600 burns, 500 micrometre spots, 0.1 to 0.2 seconds) as soon as the view allows (after anti-VEGF if the cornea is hazy), or peripheral retinal cryotherapy if the media are opaque.
• Pressure control: timolol 0.5 percent twice daily, dorzolamide 2 percent or brinzolamide 1 percent three times daily, brimonidine 0.2 percent twice daily, acetazolamide 500 mg intravenously then 250 mg four times daily, and mannitol 20 percent 1 to 1.5 g/kg for crises. Atropine 1 percent twice daily and prednisolone acetate 1 percent four times daily reduce pain and inflammation. Avoid miotics (increase inflammation) and use prostaglandins with caution.
• Surgery: glaucoma drainage device (Ahmed or Baerveldt) with anti-VEGF at the time of surgery, with a 60 to 80 percent success rate; trabeculectomy with mitomycin C is less successful because of bleeding and scarring; cyclophotocoagulation (transscleral or endoscopic) for poor visual potential.
• Blind painful eye: retrobulbar injection of 1 to 2 mL absolute alcohol or chlorpromazine 25 mg, cyclodestruction, or evisceration or enucleation.
• Treat the cause: carotid revascularisation (endarterectomy or stenting) for severe stenosis, glycaemic and blood pressure control, lipid lowering, antiplatelet therapy.
• Prognosis is guarded; early treatment before synechial closure carries the best outcome.