Neuro-ophthalmology is the branch of Ophthalmology that deals with disease of the eye in relation to the nervous system.
These fall into two main groups
- Diseases affecting the optic nerve
- Diseases affecting eye movement
OPTIC NERVE DISEASE
The optic nerve is the only nerve in the body that can be directly examined by a doctor. It connects the eye to the brain. It can be thought of as an electrical cable bringing visual information from the eye to the brain for processing.
The optic nerve can be affected by :
- Ischaemia (inadequate blood supply)
- Raised intracranial pressure
Inflammation is normally indicated by the rapid onset of the loss of vision and colour vision is frequently affected. Occasionally in inflammation affecting the optic nerve, there may be pain behind the eyes occurring especially eye movements. A diagnosis can usually be made on clinical grounds alone. However, because inflammation is often related to diseases that can affect other parts of the body, such as connective tissue disease and multiple sclerosis, some blood investigations and an MRI (Magnetic Resonance Imaging) may be necessary. Treatment with steroids may also be required.
Ischaemia usually manifests with the rapid onset of visual loss. This is usually painless. It is most commonly related to other vascular diseases such as hypertension and diabetes and is often spoken of as "a stroke of the optic nerve". Treatment is usually directed at controlled risk factors such as hypertension, diabetes, hyperlipidaemia and smoking.
Optic nerve dysfunction as a result of a compressive lesion (usually a tumour of some sort) usually exhibits slow, progressive, painless visual loss. The cause is usually apparent on Computerised Tomography (CT) Scan or MRI. A referral to neurosurgeon may be necessary.
Raised intracranial pressure can occur as a headache with early morning nausea or vomiting, transient loss vision, or focal neurological disturbances in other parts of the body (such as weakness or loss of balance). A CT Scan or MRI imaging is usually necessary, as is a lumbar puncture to obtain cerebrospinal fluid for analysis. Referral to a neurologist or neurosurgeon is usually required.
Eye movement disorders
Many diseases affect movement of the eyes. The following is a brief list of some:
- Local (eye) disease causing restriction of movement
- Disease affecting the nerves to the muscles causing weakness
- Diseases affecting the transmission of signals between nerve and muscle
- Diseases of the muscle
- Diseases affecting portions of the brain that control movement
Eye movement disorders can occur in one or more of the following ways:
- Double vision
- Blurred vision
- Unstable ("shaky") vision
The vision in each eye (when tested separately) is often normal. However, visual disturbance occurs when both eyes are used. Eye movement disorders may also be accompanied by giddiness, an unsteady gait, headaches or weakness involving other parts of the body.
Eye movement disorders that occur suddenly require urgent medical attention to rule out serious conditions such as a rupture of blood vessels supplying the brain. Investigations such as blood test , CT scan or MRI would carried out to find out the cause of the eye movement disorder.
Treatment if applicable, would usually be medical.
However, in some instances, surgery may be required.