A retinal vein occlusion occurs when one of the veins carrying blood away from the retina becomes blocked. Blood and fluid back up into retinal tissue, and vision in that eye changes — often suddenly, and usually without pain.

It is the second most common retinal vascular disorder after diabetic retinopathy, and it is frequently the first indication that a patient has an underlying vascular condition that has not yet been diagnosed.

Branch and central occlusions

The retina drains through a branching network that converges into the central retinal vein at the optic nerve. Where the blockage happens determines the pattern of vision loss.

Branch retinal vein occlusion (BRVO) involves a smaller tributary vein and affects the portion of the retina that vein drains. Vision loss corresponds to that area, so patients may notice a blurred or missing section of the visual field while the rest remains clear. If the affected area includes the macula, central vision is involved.

Central retinal vein occlusion (CRVO) involves the main vein and affects the entire retina. Vision loss is typically more pronounced and more immediately obvious.

Both types are further characterized by whether the retina remains adequately perfused, which affects both the outlook and the risk of complications.

Why it happens, and what it can indicate

Most occlusions occur where a thickened, stiffened artery crosses over a vein and compresses it, slowing flow enough for a clot to form. The conditions that stiffen arteries are therefore the conditions that raise risk:

  • High blood pressure, the most commonly associated condition
  • Diabetes
  • High cholesterol and atherosclerosis
  • Glaucoma or raised intraocular pressure
  • Smoking
  • Clotting disorders, which are considered particularly in younger patients

For this reason a vein occlusion is treated as an eye finding with systemic implications. Patients are typically referred back to their primary care physician for evaluation of blood pressure, glucose and lipids, and sometimes for further workup. Managing those factors is directed at the health of the other eye and of the patient generally, not only at the affected eye.

Signs that a vein has become blocked

  • Sudden, painless blurring or loss of vision in one eye
  • A missing or blurred section of the visual field
  • Vision that is noticeably worse on waking
  • Distortion of central vision, if the macula is involved
  • Occasionally, a gradual blur developing over days rather than at once

Pain is not typical at onset. Pain, redness and a marked rise in eye pressure appearing weeks to months later can indicate neovascular glaucoma, a complication that requires urgent attention.

How it is diagnosed

The diagnosis is usually apparent on dilated examination, where retinal hemorrhages follow the distribution of the blocked vein, together with dilated tortuous vessels and sometimes cotton wool spots.

Optical coherence tomography measures macular swelling, which is the main reason vision drops and the main target of treatment. Fluorescein angiography shows how much of the retina has lost its blood supply — an important distinction, because poorly perfused retina is what drives the growth of abnormal new vessels later.

Blood pressure is checked, and blood work is often requested through your primary care physician.

Treatment and follow-up

There is no treatment that reopens the blocked vein. Treatment is directed at the consequences, principally the macular swelling.

Anti-VEGF injections are the usual first-line treatment for macular edema following a vein occlusion, given on a repeating schedule guided by OCT. Corticosteroid implants are an alternative in selected patients. Where abnormal new vessels develop, panretinal laser is used to reduce the drive for that growth and lower the risk of neovascular glaucoma.

Follow-up continues after vision stabilizes, because complications can develop months after the initial event. Intervals are set by examination and imaging rather than by how the vision feels.

Retinal vein occlusion: common questions

The comparison is sometimes made because both involve a blocked blood vessel, but a vein occlusion blocks outflow rather than arterial supply. A blocked artery is a different and more time-critical event — see retinal artery occlusion.

Outcomes vary considerably with the type of occlusion, whether the macula is involved, and how well the retina remains perfused. Some patients regain substantial vision as swelling is treated; others are left with lasting reduction. Your physician can discuss what your particular imaging suggests rather than a general figure.

There is an increased risk compared with the general population, which is a large part of why blood pressure, glucose, cholesterol and eye pressure are addressed after the diagnosis. Managing those factors is aimed at protecting the unaffected eye.

A vein occlusion is often the first visible sign of an underlying vascular condition, most commonly high blood pressure. Evaluating and treating that condition addresses both your general health and the risk to your other eye, and it is not something managed from the eye alone.

There is no fixed course. Treatment continues while OCT shows swelling that is responding, and intervals are typically extended as the macula stabilizes. Some patients need treatment for a limited period; others require ongoing treatment. This is reviewed at each visit.

Complications such as abnormal new vessel growth and neovascular glaucoma can develop months after the occlusion, sometimes without symptoms until they are advanced. Continued examination is how those are detected while they are still straightforward to address.

Sudden vision change in one eye?

Painless loss of vision in one eye should be evaluated promptly. Call (602) 613-5473 to reach our Scottsdale office, or send us a message.