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Retinal vein occlusion

Summary
Central Retinal Vein Occlusion
Branch retinal vein occlusion
Features
Management
Risk factors
Systemic work up
References
Author(s)

Summary

Retinal vein occlusion includes vascular occlusions of either the branch or central retinal vein, resulting in potential vision changes and long term sequelae. It is the second most common retinal vascular disease after diabetic retinopathy. Retinal vein thrombosis is strongly associated with age-related local and systemic factors. The central retinal artery and the branch retinal arteriole share common adventitial sheath at arteriovenous crossings with their respective venous counterparts, and therefore atherosclerotic changes in the arteries may precipitate occlusion of the veins.

Central Retinal Vein Occlusion

In central RVO (CRVO), the occlusion is at or proximal to the lamina cribrosa of the optic nerve, where the central retinal vein exits the eye. CRVO is further divided into the categories of perfused (nonischemic) and nonperfused (ischemic).

Non ischaemic CRVO (sometimes called ‘venous stasis retinopathy’) is the more common form. 1/3rd of patients will progress to ischaemic CRVO.

Ischaemic CRVO is characterized by substantially decreased retinal perfusion with capillary closure and retinal hypoxia. Macular ischaemia and neovascular glaucoma following this are the major causes of visual morbidity.

Non-Ischaemic CRVO (Perfused)	Ischaemic CRVO (Nonperfused)
Most common type	Less common
Mild to moderate loss of acuity, usually 20/200 or better	Severe visual loss, usually less than 20/200
Mild afferent pupillary defect	Marked afferent pupillary defect
Field defect is uncommon	Field defect is common
Milder features of haemorrhage, cotton-wool spots, disc or macular oedema, and mild venous tortuosity and dilation	More severe features of haemorrhage, cotton-wool spots, disc or macular oedema, and mild venous tortuosity and dilation
FA showing delayed AV transit time, usually good retinal capillary perfusion, and some late leakage	FA showing marked delay in AV transit time, extensive areas of capillary non-perfusion and vessel wall staining and leakage
Normal ERG	Depressed ERG
Good prognosis with less chance of anterior segment neovascularization/neovascular glaucoma	Poor prognosis. High risk of neovascular glaucoma. Rubeosis iridis develops in 50% of eyes between 2-4 months.

The management of non-ischaemic CRVO is generally much less aggressive than ischaemic CRVO.

In a clearly non-ischemic CRVO without macular edema, initial follow-up should take place after 4-6 weeks to monitor for development of edema or worsening ischemia
If macular edema is present, anti-VEGF therapy is the current first-line treatment. Second line treatments typically include intravitreal triamcinolone and dexamethasone implant.
Where possible, patients with ischemic CRVO should be seen monthly for 6 months to detect the onset of anterior segment neovascularization
There is no convincing evidence of medical treatment altering the natural course of the central retinal vein occlusion itself

Color fundus photograph showing the presence of venous tortuosity with distension in CRVO. There are moderate intraretinal hemorrhages throughout the posterior pole with a greater amount of hemorrhages in a peripapillary region. Mild disk oedema appears to be present. Image Courtesy of Alasil et al.

Branch retinal vein occlusion

BRVO is a venous occlusion at any branch of the central retinal vein. Occlusions occurring at the proximal part of the central retinal vein trunk results in an hemi retinal vein occlusion (HRVO), which is considered a subtype of either CRVO or BRVO.

BRVO can be anatomically classified into ‘major’ or ‘macular’. Major BRVO refers to occlusion of a retinal vein draining one of the quadrants, whereas macular BRVO refers to occlusion of a venule within the macula. BRVO is most common in the superotemporal quadrant, felt to be due to the increase arteriovenous crossings here.

BRVO can be further classified into non-ischaemic and ischaemic ( > 5 disc diameters of nonperfusion on FA ).

Features

Sudden painless onset of blurred vision and metamorphopsia if macula is involved
Can be asymptomatic if peripheral occlusion
Chronic macular oedema is the most common cause of persistent poor visual acuity after BRVO
Retinal neovascularization occurs in about 8% of eyes by three years (higher risk in ischaemic BRVO)
Recurrent vitreous and preretinal haemorrhage, and occasionally tractional retinal detachment, can occur secondary to neovascularization

Management

Observation without intervention is usually indicated if visual acuity is 6/9 or better, or slightly worse but improving.
Laser photocoagulation was formerly the standard of treatment for macular oedema in BRVO
Neovascular glaucoma is an indication for urgent sector PRP
Intravitreal anti-VEGF agents have been widely adopted for the treatment of macular oedema. May be combined with laser.
Intravitreal dexamethasone implant and intravitreal triamcinolone

Visual improvement in BRVO is substantially superior to observation alone however carries added risk of cataract and glaucoma

Macular laser

If visual acuity remains 6/12 or worse after 3–6 months due to macular oedema and there is good central macular perfusion on FA, macular laser may be considered but treatment should not encroach within 0.5 disc diameters of the foveal centre.

Review in cases that do not require early intervention should usually take place after 3 months and then at 3–6 monthly intervals for up to 2 years, principally to detect neovascularization.

Colour fundus photograph at initial presentation showing branch retinal vein occlusion with typical retinal hemorrhage and macular oedema. Image Courtesy of Deka et al.

Risk factors

CRVO	BRVO
Hypertension	Hypertension
Open angle glaucoma	Cardiovascular disease
Diabetes mellitus	Open angle glaucoma
	High body mass index

Systemic work up

The detection and management of associated systemic disease is aimed principally at reducing the risk of future vascular occlusive events.

All patients: blood pressure, ESR, FBC, random blood glucose, LDL and HDL, plasma protein electrophoresis
Other tests to consider according to clinical picture: chest X-ray (sarcoidosis, tuberculosis, left ventricular hypertrophy), CRP, homocysteine, thrombophilia screen, autoantibodies, ACE, treponemal serology, carotid duplex imaging (to exclude ocular ischaemic syndrome)

References

John F. Salmon MD FRCS. Kanski’s Clinical Ophthalmology: A Systematic Approach. 10th edition, Elsevier, 2024.
Alasil, Tarek, and Michael E. Rauser. ‘Intravitreal Bevacizumab in the Treatment of Neovascular Glaucoma Secondary to Central Retinal Vein Occlusion: A Case Report’. Cases Journal, vol. 2, Oct. 2009, p. 176. PubMed Central, https://doi.org/10.1186/1757-1626-2-176.
Deka, Satyen, et al. ‘Rebound Effect Following Intravitreal Bevacizumab in Branch Retinal Vein Occlusion’. Oman Journal of Ophthalmology, vol. 2, no. 2, May 2009, pp. 94–95. PubMed, https://doi.org/10.4103/0974-620X.53042.
‘What Is Branch Retinal Vein Occlusion (BRVO)?’ American Academy of Ophthalmology, 16 Oct. 2023, https://www.aao.org/eye-health/diseases/what-is-branch-retinal-vein-occlusion.
‘What Is Central Retinal Vein Occlusion (CRVO)?’ American Academy of Ophthalmology, 13 Oct. 2022, https://www.aao.org/eye-health/diseases/what-is-central-retinal-vein-occlusion.

Author(s)

Dr Sara Memon

Sara is the Co-Founder of Ophtnotes. She is a doctor who graduated from UCL Medical School in London. She won the Allen Goldsmith Prize in Ophthalmology. Sara is also the co-founder of PAMSA: an organisation linking doctors and medical students of Pakistani origin. She’s especially passionate about teaching and education, having presented a workshop she designed herself at the 2019 Annual GMC Conference.