eMedicine Specialties > Ophthalmology > Retina

Central Retinal Vein Occlusion

Author: Lakshmana M Kooragayala, MD, Vitreo-retinal Surgeon, Marietta Eye Clinic
Contributor Information and Disclosures

Updated: May 26, 2009

Introduction

Background

Central retinal vein occlusion (CRVO) is a common retinal vascular disorder. Clinically, CRVO presents with variable visual loss; the fundus may show retinal hemorrhages, dilated tortuous retinal veins, cotton-wool spots, macular edema, and optic disc edema. In view of the devastating complications associated with the severe form of CRVO, a number of classifications were described in the literature. All of these classifications take into account the area of retinal capillary nonperfusion and the development of neovascular complications.^1,2,3,4,5

Broadly, CRVO can be divided into 2 clinical types, ischemic and nonischemic. In addition, a number of patients may have an intermediate in presentation with variable clinical course. On initial presentation, it may be difficult to classify a given patient into either category, since CRVO may change with time.

A number of clinical and ancillary investigative factors are taken into account for classifying CRVO, including vision at presentation, presence or absence of relative afferent pupillary defect, extent of retinal hemorrhages, cotton-wool spots, extent of retinal perfusion by fluorescein angiography, and electroretinographic changes.

Nonischemic CRVO is the milder form of the disease. It may present with good vision, few retinal hemorrhages and cotton-wool spots, no relative afferent pupillary defect, and good perfusion to the retina. Nonischemic CRVO may resolve fully with good visual outcome or may progress to the ischemic type.

Ischemic CRVO is the severe form of the disease. CRVO may present initially as the ischemic type, or it may progress from nonischemic. Usually, ischemic CRVO presents with severe visual loss, extensive retinal hemorrhages and cotton-wool spots, presence of relative afferent pupillary defect, poor perfusion to retina, and presence of severe electroretinographic changes. In addition, patients may end up with neovascular glaucoma and a painful blind eye.

Pathophysiology

The exact pathogenesis of the thrombotic occlusion of the central retinal vein is not known. Various local and systemic factors play a role in the pathological closure of the central retinal vein.^3,6,7

The central retinal artery and vein share a common adventitial sheath as they exit the optic nerve head and pass through a narrow opening in the lamina cribrosa. Because of this narrow entry in the lamina cribrosa, the vessels are in a tight compartment with limited space for displacement. This anatomical position predisposes to thrombus formation in the central retinal vein by various factors, including slowing of the blood stream, changes in the vessel wall, and changes in the blood.

Arteriosclerotic changes in the central retinal artery transform the artery into a rigid structure and impinge upon the pliable central retinal vein, causing hemodynamic disturbances, endothelial damage, and thrombus formation. This mechanism explains the fact that there will be an associated arterial disease with CRVO. However, this association has not been proven consistently, and various authors disagree on this fact.

Thrombotic occlusion of the central retinal vein can occur as a result of various pathologic insults, including compression of the vein (mechanical pressure due to structural changes in lamina cribrosa, eg, glaucomatous cupping, inflammatory swelling in optic nerve, orbital disorders); hemodynamic disturbances (associated with hyperdynamic or sluggish circulation); vessel wall changes (eg, vasculitis); and changes in the blood (eg, deficiency of thrombolytic factors, increase in clotting factors).

Occlusion of the central retinal vein leads to the backup of the blood in the retinal venous system and increased resistance to venous blood flow. This increased resistance causes stagnation of the blood and ischemic damage to the retina. It has been postulated that ischemic damage to the retina stimulates increased production of vascular endothelial growth factor (VEGF) in the vitreous cavity. Increased levels of VEGF stimulate neovascularization of the posterior and anterior segment (responsible for secondary complications due to CRVO). Also, it has been shown that VEGF causes capillary leakage leading to macular edema (which is the leading cause of visual loss in both ischemic CRVO and nonischemic CRVO).

The prognosis of CRVO depends upon the reestablishment of patency of the venous system by recanalization, dissolution of clot, or formation of optociliary shunt vessels.

Frequency

United States

CRVO and branch retinal vein occlusion constitute the second most common retinal vascular disorder. The nonischemic type is more common than the ischemic type.

In a recent publication, the Beaver Dam Eye Study Group reported the 15-year cumulative incidence of CRVO to be 0.5%.⁸

International

A large population-based study in Israel reported a 4-year incidence of retinal vein occlusion of 2.14 cases per 1000 of general population older than 40 years and 5.36 cases per 1000 of general population older than 64 years.

In Australia, the prevalence of vein occlusion ranges from 0.7% in patients aged 49-60 years to 4.6% in patients older than 80 years.⁹

Mortality/Morbidity

CRVO is not associated directly with increased mortality.

• Nonischemic CRVO may resolve completely without any complications in about 10% of cases. In about 50% of patients, vision may be 20/200 or worse. One third of patients may progress to the ischemic type, commonly in the first 6-12 months after presentation.
• In more than 90% of patients with ischemic CRVO, final visual acuity may be 20/200 or worse. Anterior segment neovascularization with associated neovascular glaucoma develops in more than 60% of cases. This can happen within a few weeks and up to 1-2 years afterward.
• It has been reported that the fellow eye may develop retinal vein occlusion in about 7% of cases within 2 years. In another report, the 4-year risk of developing second venous occlusion is 2.5% in the same eye and 11.9% in the fellow eye. Neovascular glaucoma may result in a painful blind eye.

Race

CRVO does not have any particular racial preference.

Sex

CRVO occurs slightly more frequently in males than in females.

Age

More than 90% of CRVO occurs in patients older than 50 years, but it has been reported in all age groups.

Clinical

History

A direct review of systems toward the various systemic and local factors predisposing the CRVO is indicated.

• Significant history includes the following:
  • Hypertension
  • Diabetes mellitus
  • Cardiovascular disorders
  • Bleeding or clotting disorders
  • Vasculitis
  • Autoimmune disorders
  • Use of oral contraceptives
  • Closed-head trauma
  • Alcohol consumption
  • Amount of physical activity
  • Primary open-angle glaucoma or angle-closure glaucoma
• Ocular symptoms at initial presentation
  • Asymptomatic
  • Decreased vision
  • Visual loss can be sudden or gradual, over a period of days to weeks. Visual loss ranges from mild to severe. Patients can present with transient obscurations of vision initially, later progressing to constant visual loss.
  • Photophobia
  • Painful blind eye
  • Redness of eyes
• Ocular symptoms in later stages
  • Decrease of vision
  • Pain in the eyes
  • Discomfort
  • Redness
  • Watering

Physical

Patients should undergo a complete eye examination, including visual acuity, pupillary reactions, slit lamp examination of the anterior and posterior segments, undilated examination of the iris, gonioscopy, fundus examination with indirect ophthalmoscope, and fundus contact lens.¹⁰

• Visual acuity: Best-corrected vision always should be obtained. It is one of the important indicators of the final visual prognosis.
• Pupillary reactions may be normal and may present with relative afferent pupillary reflex. If the iris has abnormal blood vessels, the pupil may not react.
• Conjunctiva: Advanced stages may show congestion on conjunctival and ciliary vessels.
• Cornea: Advanced stages may show diffuse corneal edema obscuring the visibility of internal structures.
• The iris may be normal. Advanced stages may show neovascularization. These vessels are detected best on an undilated iris. Initially, the vessels may be seen around pupillary margins and peripheral iridectomy openings if present.
• The anterior chamber angle is examined by gonioscopy. This is examined best in an undilated iris. Initially, it may show neovascularization with open angles and later show total peripheral anterior synechia and closed angles.
• Fundus examination
  • Retinal hemorrhages may present in all 4 quadrants.
  • Hemorrhages can be superficial, dot and blot, and/or deep.
  • In some patients, hemorrhages may be seen in the peripheral fundus only.
  • Hemorrhages can be mild to severe, covering the whole fundus and giving a "blood and thunder appearance."
• Dilated tortuous veins: Veins may be dilated and tortuous.
• Optic disc edema: The optic disc may be swollen during the early-stage disease.
• Cotton-wool spots are more common with nonischemic CRVO. Usually, they are concentrated around the posterior pole. Cotton-wool spots may resolve in 2-4 months.
• Neovascularization of the disc
  • Fine abnormal neovascularization of the disc (NVD) or within 1 disc diameter from the disc may be present.
  • NVD indicates severe ischemia of the retina.
  • NVD is sometimes difficult to differentiate from optociliary shunt vessels.
  • NVD can lead to preretinal or vitreous hemorrhage.
• Neovascularization elsewhere
  • Neovascularization elsewhere (NVE) is not as common as NVD.
  • NVE indicates severe ischemia of the retina.
  • NVE can lead to preretinal or vitreous hemorrhage.
• Optociliary shunt vessels are abnormal blood vessels on the disc, directing blood from retinal circulation to choroidal circulation, which indicate good compensatory circulation.
• Preretinal or vitreous hemorrhage
• Macular edema with or without exudates
• Cystoid macular edema
• Lamellar or full-thickness macular hole
• Optic atrophy
• Pigmentary changes in the macula

Causes

Central retinal vein obstruction has been associated with various systemic pathological conditions, although the exact cause and effect relationship has not been proven.

Some of the conditions in which CRVO has been associated include the following:

• Systemic vascular disease
  • Hypertension
  • Diabetes mellitus
  • Cardiovascular disease
• Blood dyscrasias
  • Polycythemia vera
  • Lymphoma
  • Leukemia
• Clotting disorders
  • Activated protein C resistance
  • Lupus anticoagulant
  • Anticardiolipin antibodies
  • Protein C
  • Protein S
  • Antithrombin III
• Paraproteinemia and dysproteinemias
  • Multiple myeloma
  • Cryoglobulinemia
• Vasculitis
  • Syphilis
  • Sarcoidosis
• Autoimmune disease - Systemic lupus erythematosus
• Oral contraceptive use in women
• Other rare associations
  • Closed-head trauma
  • Optic disc drusen
  • Arteriovenous malformations of retina
• The Eye Disease Case-Control Study Group reported that the risk of CRVO is decreased in men with increasing levels of physical activity and increasing levels of alcohol consumption. The same study group reported a decreased risk of CRVO with the use of postmenopausal estrogens and an increased risk with higher erythrocyte sedimentation rates in women.

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