Retinal Vein Occlusion

Ischemic central retinal vein occlusion.

Non-ischemic hemi-retinal vein occlusion.

Signs and Symptoms: The patient presenting with retinal vein occlusion will usually be elderly, often with systemic diseases such as diabetes and hypertension. He or she may be asymptomatic, but often will complain of a sudden painless unilateral loss of vision and/or visual field. The patient may complain of a sudden onset of floating spots or flashing lights. Acuity may range anywhere from 20/20 to finger counting. If vision loss is severe, a relative afferent pupillary defect may exist, indicative of retinal ischemia.

Ophthalmoscopically, you will note retinal edema, superficial hemorrhages, disc swelling, cotton-wool spots and tortuous and dilated retinal veins. With a central retinal vein occlusion (CRVO), these findings will appear in all four quadrants. A hemi-central retinal vein (HRVO) occlusion will involve only the superior or inferior half of the retina. A branch retinal vein occlusion (BRVO) will manifest these findings--although the tortuous veins may only appear in the most severe cases of BRVO--in only one quadrant; usually the superior-temporal sector, with the apex of the hemorrhaging at an arteriovenous crossing.

The hemorrhaging in any case may be so severe that all features of the underlying retina are obscured. The presence of multiple cotton wool spots indicates retinal ischemia and capillary non-perfusion. Anterior and posterior segment neovascularization may occur later in the course of the disease. Anterior segment neovascularization arises from cases of CRVO and posterior segment neovascularization more commonly occurs from BRVO or HRVO.

Pathophysiology: The etiology of central and hemi-central retinal vein occlusion is an obstruction of the central retinal vein, or one of the vein's two trunks, as it constricts through the lamina cribrosa. The cause is obscure, but may involve abnormal blood flow or blood constituents, atherosclerosis, vessel anomalies or a combination of factors.

The etiology of BRVO is an arteriolosclerotic arteriole crossing and constricting the underlying venule. This will result in leakage from the capillary beds draining into these vessels. This leakage may irreversibly damage the capillary beds, resulting in perpetual non-perfusion of the retinal tissue. If a significant area of capillary non-perfusion is present, then the occlusion is considered ischemic.

Loss of retinal capillary beds with subsequent retinal non-perfusion will lead to retinal hypoxia and the subsequent release of vasoproliferative chemicals. Vasoproliferative factors will then stimulate the proliferation of neovascularization from nearby viable capillary beds.

In the case of branch and hemi-central occlusions, neovascularization will most often form on the optic disc or adjacent retina. In such cases, neovascularization can lead to vitreous hemorrhage and tractional retinal detachment. In central retinal vein occlusions, the closest viable capillary network from which neovascularization will form is the posterior iris. This can lead to rubeosis irides and neovascular glaucoma.

In venous occlusion, macular edema is the main cause of vision loss. With macular edema, visual acuity is typically better than 20/200. However, if retinal capillary non-perfusion involves the perifoveal region, then vision is dramatically reduced (typically finger-counting) and irreversibly lost.

Management: Fluorescein angiography, while long held to be the gold standard in assessing retinal vascular disease, has questionable use in vein occlusions. This procedure is not indicated initially because the fresh hemorrhage will block transmission and reveal no useful information. Later in the course of the occlusion, angiography will give information about retinal capillary perfusion and whether or not the occlusion is ischemic and thus more likely to develop neovascular complications.

Research has indicated that ischemic retinal vein occlusions do not benefit from prophylactic pan-retinal photocoagulation. Withhold this procedure until the patient develops frank neovascularization of the iris, disc or retina.

Non-ischemic branch retinal vein occlusion.

Monitor the patient with serial ophthalmoscopy, fundus photography (if possible) and gonioscopy monthly until resolution is evident. Observe closely for neovascularization of the disc, retina, iris and angle. Follow patients with ischemic CRVO every two weeks, paying particular attention to possible neovascularization in the iris. After three months, it's appropriate to follow these patients monthly. If neovascularization develops, then pan-retinal photocoagulation is indicated.

If the patient has a hemi-central or branch retinal vein occlusion and vision is reduced below 20/40 due to macular edema, then the patient may benefit from focal laser photocoagulation anywhere between 3-18 months after the occlusion onset. CRVO patients with vision reduction due to macular edema do not benefit from focal laser photocoagulation.

Because vein occlusions are often associated with systemic disease, co-manage the patient with an internist. (For a list of tests to consider, see table.)

Clinical Pearls:

• Tests for Patients With Retinal Vein Occlusions Blood pressure Fasting blood-glucose, lipid and cholesterol studies FTA-ABS Complete blood count with differential Sickledex (if the patient is black) Anti-nuclear antibodies Angiotensin converting enzymes Antiphospholipid antibodies Viscosity studies

  The management of vein occlusions involves monitoring for resolution or late complications, laser intervention if neovascular complications develop, and systemic comanagement with an internist.
• Ischemic vein occlusions typically present with acuity worse than 20/200. Those eyes with initial acuity better than 20/200 are at very low risk of developing severe vision loss (vision less than 20/400) and are likely to resolve.
• Ischemic occlusive disorders are likely to present with a relative afferent pupillary defect. If this is not present, then it is likely non-ischemic.
• The systemic diseases most associated with retinal vein occlusions are hypertension and diabetes.