Ischemic CRVO: Signs, Risks and Management

Ischemic CRVO is the severe form of central retinal vein occlusion, with extensive capillary nonperfusion and poor vision.

It carries a high risk of iris neovascularization and neovascular glaucoma.

Therefore, early recognition and close follow-up protect the eye from a painful end stage.

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Defining Ischemic CRVO

The Central Vein Occlusion Study defined ischemic disease as ten or more disc areas of capillary nonperfusion on fluorescein angiography.

Clinicians also use visual acuity, pupil response and the extent of hemorrhage.

Also, the line between ischemic and nonischemic disease is not sharp.

Therefore, repeat the assessment over time.

How Common Is Ischemic CRVO

Most eyes with central retinal vein occlusion are nonischemic at presentation.

A minority are ischemic, and some perfused eyes convert later.

Also, the Central Vein Occlusion Study found that a proportion of perfused eyes became nonperfused within three years.

Because conversion happens, follow all eyes.

Clinical Signs of Ischemic CRVO

Visual acuity is usually 20/200 or worse.

A relative afferent pupillary defect is common.

Also, the retina shows dense hemorrhages in all quadrants, venous dilation and cotton-wool spots (see central retinal vein occlusion).

Therefore, a dramatic fundus with poor vision suggests ischemia.

Fluorescein Angiography

Angiography shows large areas of nonperfusion and blocked fluorescence from hemorrhage.

It helps confirm the diagnosis when the signs are mixed.

Also, ultra-widefield imaging reveals peripheral nonperfusion (see fluorescein angiography).

Because the test is not always possible, use the clinical signs too.

Risk of Neovascularization

Hayreh and others described a high rate of neovascularization in ischemic eyes.

Iris and angle vessels often appear within the first six months.

Also, the risk is higher with extensive nonperfusion and poor acuity.

Therefore, examine the iris and the angle regularly (see rubeosis iridis).

Monitoring Schedule for Ischemic CRVO

Review monthly for the first six months.

At each visit, check the iris and the angle by gonioscopy before dilation.

Also, measure the pressure and examine the fundus.

Because angle neovascularization can precede changes on the iris, gonioscopy is essential.

Treatment of Neovascularization

Panretinal photocoagulation reduces the stimulus for vessel growth.

The Central Vein Occlusion Study did not support prophylactic treatment but supported prompt treatment when neovascularization appears (see panretinal photocoagulation).

Also, anti-VEGF injections cause rapid regression of vessels.

Therefore, combine injections with laser in many eyes.

Neovascular Glaucoma

Neovascular glaucoma causes a rapid rise in pressure and severe pain.

Treat the pressure, the neovascularization and the pain together (see neovascular glaucoma).

Also, tube surgery or cyclodestruction may be needed.

Because the visual outcome can be poor, early action matters.

Macular Edema in Ischemic CRVO

Macular edema accompanies many eyes.

Anti-VEGF drugs reduce the thickness and may improve vision.

Also, the improvement is smaller in ischemic eyes because of macular damage.

Therefore, set realistic expectations.

Systemic Evaluation

Check the blood pressure, glucose and lipids.

Ask about glaucoma, hyperviscosity and clotting disorders in young patients.

Also, refer for systemic assessment when risk factors are present.

Because the other eye can be affected, treat the systemic causes.

Prognosis of Ischemic CRVO

Vision often stays poor in ischemic eyes.

Some patients maintain a useful level of vision in the fellow eye.

Also, neovascularization can be prevented in many eyes with timely treatment.

Counseling the Patient

Explain the risk of pain and vision loss from glaucoma.

Also, explain the schedule of visits and the reason for each.

Because adherence matters, give clear written instructions.

Bedside Clues to Ischemia

Check the pupil for a relative afferent defect.

Look at the retina for dense hemorrhages and multiple cotton-wool spots.

Also, ask about visual acuity.

Because bedside signs help when angiography is delayed, use them to decide on urgency.

Role of Optical Coherence Tomography Angiography

OCTA shows the macular capillary dropout without dye.

It can help judge ischemia in cooperative patients.

Also, wide-field systems extend the view.

Therefore, it may complement fluorescein.

Anti-VEGF and Retinal Perfusion

Injections do not restore perfusion.

They treat edema and new vessels.

Also, treatment may mask the need for laser if the eye is not followed.

Because ischemia persists, continue to monitor.

Systemic Associations

Hypertension, diabetes and hyperlipidemia are common.

Also, glaucoma and hyperviscosity states contribute.

Therefore, send the patient for a medical review.

Follow-Up in the Long Term

Check the fellow eye and the systemic risk factors.

Also, remind patients to return if pain occurs.

Because late neovascularization can occur, do not stop follow-up too early.

For the latest studies, see the PubMed results for ischemic CRVO.

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References

1. Central Vein Occlusion Study Group. Natural history and clinical management of central retinal vein occlusion. Arch Ophthalmol. 1997;115:486-491.
2. Central Vein Occlusion Study Group. A randomized clinical trial of early panretinal photocoagulation for ischemic central vein occlusion: the CVOS Group N report. Ophthalmology. 1995;102:1434-1444.
3. Hayreh SS, Klugman MR, Beri M, Kimura AE, Podhajsky P. Differentiation of ischemic from non-ischemic central retinal vein occlusion during the early acute phase. Graefes Arch Clin Exp Ophthalmol. 1990;228:201-217.
4. McIntosh RL, Rogers SL, Lim L, et al. Natural history of central retinal vein occlusion: an evidence-based systematic review. Ophthalmology. 2010;117:1113-1123.