Aetiology

Retinal vein occlusion (RVO) is the second most common retinal vascular disorder after diabetic retinopathy, affecting 0.77% of the global population aged 30 years or older.

The most common aetiological factor is vein wall compression by adjacent atherosclerotic retinal arteries. Other possible causes are disease of the vein wall, e.g. vasculitis or blood constituent abnormalities

RVO occurs following a complete or partial obstruction in the central retinal vein or one of its branches

• Central retinal vein occlusion (CRVO): thrombosis of the central retinal vein at the lamina cribrosa or a retrolaminar location
• Branch retinal vein occlusion (BRVO): venous thrombosis occurring typically at an arteriovenous crossing, where the artery and vein share a common vascular sheath. Six to seven times more common than CRVO. Up to two-thirds of BRVOs occur in the superotemporal quadrant
• Hemi-retinal vein occlusion (HRVO): occlusion occurring at the optic disc involving the superior or inferior hemifield and considered a mild form of CRVO with the same underlying aetiology and similar natural history

CRVO and BRVO can be broadly classified as ischaemic or nonischaemic based on the degree of capillary non-perfusion on fluourescein angiography; however, it is now known that all vein occlusions are ischaemic to varying degrees

The two main vision-threatening complications of RVO are macular oedema and retinal ischaemia, leading to poor vision, iris and retinal neovascularisation and possibly neovascular glaucoma

Secondary macular oedema is the most common cause of visual loss in RVO. 75% of patients with CRVO develop macula oedema within 2 months of diagnosis and 5% to 15% with BRVO within the first year

A person with a CRVO has a 5% per year chance of developing a CRVO in the fellow eye

A person with a BRVO has a 10% risk of developing a RVO in the fellow eye over 3 years

All patients with RVO are at an increased risk of future cardiovascular disease

Predisposing factors

Older age (most common in 6th to 7th decade; uncommon in those under 40)

The three most common risk factors:

• arterial hypertension
• diabetes mellitus
• hyperlipidaemia

Other factors include:

• glaucoma
• history of myocardial infarction or stroke
• blood coagulation disorders
• systemic vascular inflammatory disorders

Symptoms of retinal vein occlusion

Sudden or gradual painless loss of vision or visual field defect. The degree of visual impairment is dependent on the site and severity of the occlusion and its impact on retinal perfusion.

BRVO: extent of visual impairment is determined by the degree of macular involvement (oedema and/or ischemia) (incidence 30%). May be asymptomatic (particularly nasal BRVO)

Signs of retinal vein occlusion

Non-Ischaemic CRVO

• acuity usually ≥6/30
• mild tortuosity and dilation of branches of the central retinal vein; dot/blot and flame-shaped haemorrhages; optic disc, retinal and macular oedema; cotton-wool spots may be present
• ±RAPD
• 25–34% of cases non-ischaemic CRVO convert to the ischaemic subtype within 3 years

Ischaemic CRVO

• acuity usually <6/36
• capillary closure and retinal hypoxia causes severe tortuosity and engorgement of branches of the central retinal vein, extensive deep blot and flame-shaped haemorrhages; numerous cotton wool spots; severe macular/disc oedema
• RAPD
• iris neovascularisation (rubeosis iridis) develops in approx. 50% of eyes after 2-4 months
• new vessels elsewhere on the retina (NVE) or the disc (NVD)
• risk of rubeotic glaucoma causing increased IOP and eye pain (typically after 3  months (90-day glaucoma) but can occur between 2 weeks and 2 years following RVO)
• vitreous haemorrhage
• tractional retinal detachment

BRVO

• classically wedge-shaped retinal involvement that follows the distribution of the affected vein. Flame haemorrhages, dot and blot haemorrhages, cotton wool spots, hard exudates, retinal oedema, and dilated tortuous veins (signs more extensive if the occlusion is ischaemic compared to a non-ischaemic BRVO.
  NVE and NVD likely in ischaemic occlusions)

Differential diagnosis

Ocular ischaemic syndrome
Asymmetrical diabetic retinopathy
Idiopathic retinal telangiectasia (type 1)
Hypertensive retinopathy
Choroidal neovascularisation (can be distinguished by choroidal/RPE involvements on imaging)

Management by optometrist

Practitioners should recognise their limitations and where necessary seek further advice or refer the patient elsewhere

Prior to referral, baseline assessment should consist of:

• best corrected visual acuity
• colour fundus photography
• gonioscopy (if available and if ischaemic CRVO is suspected)
• optical coherence tomography (OCT) (if available)
• IOP check

(GRADE*: Level of evidence=low, Strength of recommendation=strong)

None

Management category

A3 (modified): Urgent referral to an ophthalmologist (to be seen within 2-4 weeks from presentation) PLUS Urgent referral to GP for medical management and investigation.

Possible management by ophthalmologist

Investigations:

• OCT
• fluorescein angiography and /or OCT angiography
• gonioscopy (if ischaemic CRVO is suspected)
• ultrasound, especially where the retina cannot be directly visualised, for example where there is vitreous haemorrhage
• blood tests, including FBC, serum glucose and ESR (especially in younger patients <50 years)

Treatment is directed at vision-threatening complications e.g. macular oedema and neovascularisation:

• intravitreal anti-VEGF injections is the usual first line treatment for macula oedema secondary to CRVO. There are two licenced options, ranibizumab (Lucentis) and aflibercept (Eylea)
• alternative treatment includes intravitreal steroid, e.g. Ozurdex (dexamethasone implant) 
• macular laser no longer recommended as first line therapy, but pan-retinal photocoagulation is indicated in CRVO with retinal, disc, iris or angle new vessels

Monitoring for iris/angle/retinal neovascularisation

Evidence base

*GRADE: Grading of Recommendations Assessment, Development and Evaluation (see www.gradeworkinggroup.org)

Sources of evidence

Braithwaite T, Nanji AA, Lindsley K, Greenberg PB. Anti-vascular endothelial growth factor for macular oedema secondary to central retinal vein occlusion. Cochrane Database Syst Rev. 2014;(5):CD007325

Flaxel CJ, Adelman RA, Bailey ST, Fawzi A, Lim JI, Vemulakonda GA, Ying GS. Retinal Vein Occlusions Preferred Practice Pattern. Ophthalmology. 2020;127(2):288-320

Gewaily D, Muthuswamy K, Greenberg PB. Intravitreal steroids versus observation for macular edema secondary to central retinal vein occlusion. Cochrane Database Syst Rev. 2015;(9):CD007324

Havens SJ, Gulati V Neovascular glaucoma. Dev Ophthalmol. 2016;55:196-204

Khan Z, Almeida DR, Rahim K, Belliveau MJ, Bona M, Gale J. 10-Year Framingham risk in patients with retinal vein occlusion: a systematic review and meta-analysis. Can J Ophthalmol. 2013;48(1):40-45.e1

Lam FC, Chia SN, Lee RM. Macular grid laser photocoagulation for branch retinal vein occlusion. Cochrane Database Syst Rev. 2015;(5):CD008732

Mitry D, Bunce C, Charteris D. Anti-vascular endothelial growth factor for macular oedema secondary to branch retinal vein occlusion. Cochrane Database Syst Rev. 2013;(1):CD009510

Nicholson L, Talks SJ, Amoaku W, Talks K, Sivaprasad S. Retinal vein occlusion (RVO) guideline: executive summary. Eye (Lond). 2022;36(5):909-912.

Rogers S, McIntosh RL, Cheung N, Lim L, Wang JJ, Mitchell P, Kowalski JW, Nguyen H, Wong TY; International Eye Disease Consortium. The prevalence of retinal vein occlusion: pooled data from population studies from the United States, Europe, Asia, and Australia. Ophthalmology. 2010;117(2):313-9.e1. 

Shalchi Z, Mahroo O, Bunce C, Mitry D. Anti-vascular endothelial growth factor for macular oedema secondary to branch retinal vein occlusion. Cochrane Database Syst Rev. 2020;7(7):CD009510.

Song P, Xu Y, Zha M2, Zhang Y, Rudan I. Global epidemiology of retinal vein occlusion: a systematic review and meta-analysis of prevalence, incidence, and risk factors. J Glob Health. 2019;9(1):010427

Retinal vein occlusion
Version 2
Date of search 23.04.22
Date of revision 01.02.24
Date of publication 14.09.22
Date for review 22.04.24
© College of Optometrists