Definition
Sudden onset painless loss of vision is usually due to vascular occlusion. There are two types of vascular occlusions discussed in this article.
Central Retinal Vein Occlusion
The first – CRVO (Central Retinal Vein Occlusion), is the second most common vascular pathology which affects the retina. The most common being diabetic retinopathy (discussed in another article). The subtype of retinal vein occlusion depends on the location of the blockage. There are 3 sub-types: CRVO, BRVO (Branch retinal vein occlusion) and HRVO (hemi-retinal vein occlusion).
Causes
Causes re ischaemic and non-ischaemic. CRVO is the most common cause of painless loss of vision in the eye.
Risk factors include:
- Hypertension
- Age (over 50)
- Diabetes
- High cholesterol
- Smoking
- Hyper-coagulability
- Oral contraceptives (COCPs)
- Auto-immune pathologies e.g. Sarcoid
Clinical Features
- Sudden, painless loss of vision
- Metamorphopsia (if macular effected)
- RAPD can occur
On Fundoscopy
- Dot blot haemorrhages
- Flame haemorrhages
- Macular oedema
- Cotton wool spots
- RAPD
Treatment
Specific ocular treatment will depend on location, severity of oedema and extent of visual loss. It will be determined by the Ophthalmology specialist team.
The patient should be followed up and monitored by GP for high blood pressure and diabetes assessment.
Specific ocular treatment options for CRVO include:
- Laser & Anti-VEGF (if new vessel growth)
- Intravitreal steroids (if macular oedema)
Central Retinal Artery Occlusion
The second type of occlusion is CRAO (Central Retinal Artery Occlusion). It is an emergency ophthalmic presentation.
Causes
Causes are like that of occlusion elsewhere in the body and are usually a result of embolus formation elsewhere in the body, becoming dislodged and causing a blockage in the central retinal artery.
Risk Factors
Risk factors include:
- Hypertension
- Age
- Diabetes
- High cholesterol
- Smoking
- Hyper-coagulability
- Oral contraceptives (COCPs)
Clinical Features
- Sudden, painless loss of vision
- Bruit/arrythmias may be present
- Ensure to assess cardiovascular risk factors
On Fundoscopy
- Pale retina with cherry red spot.
- The cherry red spot is due to the central part of the macular having a blood supply from the choroid in addition to the retinal vessels, hence the blood supply is preserved, maintain its red colour.
- Papilloedema
- New vessel growth
Referral Pathway
Any suspicion of painless visual loss should prompt urgent referral to Ophthalmology as per local guidelines. Suspected work-up for CRAO should prompt echo, ECG and carotid doppler.
- Referral to the stroke team is also required in this instance
Treatment
Specific options for CRAO:
The mainstay of treatment is to perform a full stroke workup and treat this accordingly.
Most ocular interventions unfortunately have a mixed evidence base, but options include:
- Immediate digital ocular massage to attempt to dislodge the clot (if presented within 90 minutes)
- Intra-ocular pressure reduction with eye drops
- Hyperventilation/induction of respiratory acidosis to achieve vasodilation.
References
Image 1 – https://en.wikipedia.org/wiki/Central_retinal_artery_occlusion
Image 2 – https://www.ophthalmologyexpertservices.com/blog/2019/central-retinal-vein-occlusion
Written by Dr Shuchi Kohli (FY3) & reviewed by Mr Ernest Lim (Ophthalmology ST5)
