Diseases
Posterior Ischaemic Optic Neuropathy (NOIA)
Other terms
- Optic nerve infarction
Definition
The optic nerve originates in the eye socket and carries visual signals to the brain. Each optic nerve contains millions of neuronal fibres. Optic neuropathies are diseases of the optic nerve, the most common of which is glaucoma. Other optic neuropathies include optic neuritis, which is an inflammation of the optic nerve, and ischaemic optic neuropathies, which are diseases that disrupt blood flow to the optic nerve, causing damage that is often irreversible.
A distinction is made between anterior ischaemic optic neuropathy (AION), where the optic disc (optic nerve head) is affected, and posterior ischaemic optic neuropathy, where the optic disc is normal.
In NOIA, there is a sudden loss of vision due to the interruption or reduction of blood flow to the optic disc. There are two types of NOIA:
Arteritic NOIA, caused by inflammation of the arteries (vasculitis)
Non-arteritic NOIA, which are non-inflammatory.
Causes
Ischaemic optic neuropathy is caused by damage to the blood vessels supplying the optic nerve:
- Cardiovascular diseases or risk factors (such as high blood pressure, high cholesterol or diabetes)
- Smoking
- Lesions or tumours compressing the vessels
- Sleep apnoea
One of the most common causes of arterial NOIA is giganto-cellular arteritis (or Horton's disease).
The most frequent cause of non-arteritic NOIA is arteriosclerosis (or atherosclerosis), which corresponds to a rigidification and reduction of the internal surface of the arteries following the formation of deposits on their internal wall.
Symptoms
The main symptom of ischaemic optic neuropathy is a sudden, painless loss of vision, the extent and location of which depends on the damage to the optic nerve. The likelihood of NOIA in one eye is greater if the other eye has already been affected.
NOIA can sometimes be preceded by warning signs to which you should be alert. This is the case, for example, with transient obscuration of vision, which can last from a few seconds to a few minutes, and which requires an ophthalmological consultation without delay in order to avoid excessive visual loss.
Diagnosis
The ophthalmologist will look for signs of ischaemia in the eye. To do this, he will examine the back of the eye to observe the retina, the papilla and the blood vessels.
He will also carry out :
- A visual acuity and visual field test
- Measurement of intraocular pressure
- A blood test to check for inflammation
Additional tests may be suggested depending on suspected risk factors (e.g. diabetes, hypertension or sleep apnoea).
Treatments
There is no treatment that can restore the vision lost as a result of NOIA. Only vision aids, such as magnifying glasses, can be offered.
In the case of arterial NOIA, oral treatment with corticosteroids can prevent a relapse and protect the other eye. It is important to start this treatment as soon as possible. Corticosteroids are administered in high doses for two to three weeks, after which the dose is gradually reduced. However, it should be noted that lifelong treatment may be necessary.
For non-arteritic NOIA, the main treatment is based on treating the underlying causes (e.g. diabetes, cardiovascular disease, hypertension).
Arteritic NOIA generally causes greater vision loss than non-arteritic NOIA, where visual recovery occurs spontaneously in 40-50% of cases.
Frequency
NOIA mainly affects people over the age of 50.
The non-arteritic form is the most common (around 95% of NOIA). Its prevalence after the age of 50 is 2 to 10 per 100,000 people.
References
Neuropathies optiques ischémiques - EM consulte (em-consulte.com)
Anterior Ischemic Optic Neuropathy (AION) (clevelandclinic.org)
What Is Ischemic Optic Neuropathy? - American Academy of Ophthalmology (aao.org)