Retinal Vein Occlusions
The central retinal vein is the main vein that drains blood from the retina.
An obstruction can cause sudden and painless vision loss. It may involve the main vein or one of its branches.
Each type has different causes, prognosis, and treatment.
Causes
In the case of branch retinal vein occlusion (BRVO), the most common causes include high blood pressure, heart disease, obesity, and a history of glaucoma (elevated intraocular pressure). In younger patients, it may also be related to blood clotting disorders of various kinds.
Central retinal vein occlusion (CRVO) is associated with high blood pressure, diabetes, carotid artery insufficiency, and increased blood viscosity. It is also linked to glaucoma (elevated intraocular pressure), the use of oral contraceptives and diuretics, and systemic inflammatory disorders such as lupus, syphilis, sarcoidosis, and HIV.
Symptoms
There is significant vision loss that is painless and usually sudden, although it may sometimes develop gradually over days or weeks.
In branch retinal vein occlusion, partial visual field loss occurs, though central vision may sometimes be affected.
In central retinal vein occlusion, there is generalized vision loss (both central and peripheral). It may also cause abnormal blood vessel growth in the retina or iris, which can bleed or lead to a painful eye (neovascular glaucoma).
Diagnosis
Diagnosis is based on clinical findings, assessment of systemic history, and risk factors. Evaluation includes measurement of visual acuity, examination of the anterior segment, and a fundus examination.
The examination helps differentiate vein occlusion from other conditions that may cause retinal hemorrhages (such as diabetes or carotid obstruction). In central vein occlusion, the veins may appear engorged (dilated), and the front part of the optic nerve may be swollen.
Fluorescein angiography: In this test, the doctor injects a dye into a vein in the arm and takes photographs of the retina. It is very useful for determining the extent of retinal damage and assessing perfusion.
Optical coherence tomography (OCT): Used to evaluate macular edema (retinal swelling) and to monitor treatment effectiveness.
Visual field testing: In branch occlusions (partial blockages), it helps assess the affected area of the visual field.
Once venous occlusion is diagnosed, additional tests are required to identify factors that increase the risk of thrombosis. Depending on suspected conditions, tests may be performed to detect diabetes, glaucoma, hypertension, and disorders that increase blood thickness (hyperviscosity).
Treatment
Most individuals experience some degree of permanent vision loss.
If vision is good at the time of the occlusion (generally when only a branch is blocked), it is likely to remain good, sometimes nearly normal.
If vision was poor (20/200) at diagnosis, it usually remains poor or may worsen in the first few days.
Treatment is directed at managing macular edema (swelling of the central retina) and complications.
Macular edema is treated with intraocular injections. Medications that may be injected include:
- Anti-angiogenic agents (Lucentis, Eylea, Avastin)
- Corticosteroids (Ozurdex)
Sometimes these treatments must be combined.
In branch occlusion, laser treatment may also be used.
Abnormal or bleeding blood vessels are treated with retinal laser therapy. (In branch occlusion, this may involve only part of the retina.) This is necessary to prevent further vision loss from intraocular hemorrhage or neovascular glaucoma.
Surgical treatment: Vitrectomy may sometimes be necessary in cases of complications such as intraocular bleeding or neovascular glaucoma (significant elevation of eye pressure) that does not respond to laser photocoagulation.
Although treatments help improve vision in many people, others may still experience some permanent vision loss.
The best approach is prevention by controlling risk factors such as hypertension, diabetes, obesity, and high cholesterol.