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What Is Neovascularization of the Iris (NVI)?

Neovascularization of the iris, or NVI, is growth of fine new blood vessels on the iris surface and at the pupillary border. It usually indicates severe posterior segment ischemia and a high level of angiogenic factors in the eye. These new vessels are fragile and can bleed, but the greatest concern is their extension into the anterior chamber angle. There, they form fibrovascular tissue that can block aqueous outflow and cause neovascular glaucoma. NVI is a serious warning sign that needs urgent evaluation.

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What Is Neovascularization of the Iris (NVI)?

Neovascularization of the iris, or NVI, is growth of fine new blood vessels on the iris surface and at the pupillary border. It usually indicates severe posterior segment ischemia and a high level of angiogenic factors in the eye. These new vessels are fragile and can bleed, but the greatest concern is their extension into the anterior chamber angle. There, they form fibrovascular tissue that can block aqueous outflow and cause neovascular glaucoma. NVI is a serious warning sign that needs urgent evaluation.

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Causes and Mechanisms of NVI

NVI most often arises in eyes with proliferative diabetic retinopathy, ischemic central retinal vein occlusion, or carotid artery occlusive disease. Extensive retinal hypoxia raises intraocular levels of vascular endothelial growth factor. This stimulates new vessel growth not only in the retina but also on the iris and angle structures. As the abnormal vessels mature, fibrous tissue accompanies them and contracts. Angle closure by this membrane elevates intraocular pressure and can cause painful, difficult to control glaucoma.

Clinical Features and Stages

Early NVI may show only delicate tufts at the pupillary margin, which can be hard to see without careful slit lamp examination. As it progresses, a fine network covers the iris surface and invades the trabecular meshwork. Redness, photophobia, and mild ache can occur, but some patients are asymptomatic until pressure rises. When neovascular glaucoma develops, pain, decreased vision, corneal edema, and a mid dilated poorly reactive pupil are common. Gonioscopy reveals fibrovascular tissue over the angle.

Diagnosis and Evaluation

Diagnosis is made by slit lamp examination of the iris and pupillary border, often with high magnification and bright light. Gonioscopy is used to inspect the angle for early neovascularization and synechial closure. The clinician then searches for the underlying ischemic cause with dilated fundus examination and imaging. Fluorescein angiography can show widespread retinal ischemia and leakage from neovascular areas. Carotid Doppler ultrasound or other vascular studies are considered when ocular ischemic syndrome is suspected.

Treatment and Prognosis

Treatment aims to reduce ischemic drive, control intraocular pressure, and relieve pain. Panretinal photocoagulation treats ischemic retina and lowers production of angiogenic factors. Intravitreal anti VEGF injections can cause rapid regression of iris neovascularization, especially in the short term. Pressure lowering drops, systemic medications, and sometimes surgery or cyclodestructive procedures are used to manage glaucoma. Prognosis depends on how advanced NVI and glaucoma are at diagnosis and on the severity of the underlying disease.

FAQs About NVI

Is NVI the same as normal iris blood vessels?

No, normal iris vessels are deeper and not easily seen, while NVI appears as fine, abnormal surface vessels that grow toward the pupil and angle.

Can NVI go away on its own?

It usually persists or worsens without treatment. Regression is more likely when ischemia is addressed with laser and anti VEGF therapy.

Does everyone with diabetic retinopathy develop NVI?

No, NVI occurs mainly in advanced, poorly controlled, or very ischemic disease. Regular eye care helps reduce this risk.

Why is NVI linked with severe glaucoma?

The new vessels and fibrous tissue can cover the drainage angle, blocking fluid outflow and causing very high intraocular pressure.

References

Moran CORE. ?Neovascularization of the Iris (Rubeosis Iridis).? https://morancore.utah.edu/section-10-glaucoma/neovascularization-of-the-iris-rubeosis-iridis/

University of Iowa, EyeRounds. ?Rubeosis iridis or neovascularization of the iris in diabetes.? https://webeye.ophth.uiowa.edu/eyeforum/atlas/pages/NVI/index.htm

EyeWiki. ?Neovascular Glaucoma.? https://eyewiki.org/Neovascular_Glaucoma

American Academy of Ophthalmology (AAO). ?Diagnosis and Management of Neovascular Glaucoma.? https://www.aao.org/eyenet/article/diagnosis-and-management-of-neovascular-glaucoma

NCBI Bookshelf. ?Neovascular Glaucoma (StatPearls).? https://www.ncbi.nlm.nih.gov/books/NBK576393/