Neuro-Ophthalmology

Neuro-Ophthalmic conditions include Optic Neuropathies and Eye Movement Disorders.

The optic nerve is the only nerve in the body that can be directly examined by a doctor. Similar to an electrical cable, it connects the eye to the brain, bringing visual information for processing.

It can be affected by:

• Inflammation

Inflammation of the optic nerve can be due to infections, vaccination or autoimmune conditions.

• Ischemia (inadequate blood supply)

Commonly known as “stroke of the optic nerve”, Ischemia occurs when the optic nerve receives inadequate blood supply and oxygen. It is commonly related to other vascular diseases such as hypertension and diabetes.

• Compression

Compression of the optic nerve can be caused by benign or malignant tumours, blood vessels or enlargement of normal structures within the orbit.

• Raised intracranial pressure

Raised intracranial pressure, or rise in pressure around the brain, may be accompanied by other non-visual symptoms.

• Trauma
• Drugs and Toxins

Eye Movement Disorders can be a result of brain, nerve, neuromuscular junction or muscle pathology. At times, abnormal movement or balance of the eyes can be related to a problem elsewhere, like the ears.

Many diseases affect movement of the eyes. These include:

• Local (orbital) 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

The vision in each eye (when tested separately) is often normal. However, visual disturbance occurs when both eyes are used.

Eye Movement Disorders that occur suddenly require urgent medical attention to rule out serious conditions such as the rupture of blood vessels supplying oxygen to the brain.

Investigation and treatment is directed at the cause of the Eye Movement Disorder.

Optic Neuropathies can present in one or more of the following ways:

Inflammation

• Loss of vision over 2-3 days, frequently affecting colour vision. It can cause occasional pains behind the eyes, especially during eye movements.

Ischemia

• Acute, painless loss of vision

Compression

• Slow, progressive, painless or painful loss of vision.

Raised intracranial pressure

• Headache with early morning nausea or vomiting, transient loss of vision, or focal neurological disturbances in other parts of the body (such as weakness or loss of balance).

Eye Movement Disorders can present in one or more of the following ways:

• Double vision
• Blur vision
• Unstable (“shaky”) vision
• dizziness
• unsteady gait
• headaches
• weakness involving other parts of the body

Neuro-Ophthalmic problems tend to be more complex, requiring longer consultation and investigations. During the first visit to the clinic, patients can expect to spend up to two to three hours for consultation.

Driving on the day of consultation is not advised, you are advised to bring along your glasses and any old medical records. Depending on your symptoms, your doctor may perform perimetry, imaging of your nerves and retina, MRI scans and blood tests.

'Electrical testing of vision', so called 'visual electrophysiology', is a measurement of the very small signals generated by the eye and the brain in response to what we see or look at. These signals provide information regarding the eye, nerve and brain function that helps the doctor make decisions on diagnosis and treatment.

The main reasons for visual electrophysiology are:

• To confirm or exclude a suspected diagnosis
• Unknown diagnosis
• To determine the characteristics and severity of disease
• To monitor the disease before and after treatment

You can expect to take a series of tests including Electroretinogram (ERG), Pattern Electroretinogram (PERG), and Visual Evoked Potential (VEP) tests.

It can take up to three hours to complete all the tests, but they are all non-invasive, and it is rarely necessary to use numbing drops in the eye. There are no injections into the eye or arm. The drops used to dilate the pupils may cause a slight stinging sensation for a few seconds, and vision will be blurred for a few of hours after testing, so you should refrain from driving. Dark glasses may help on a sunny day. Patients having a VEP will usually wash their hair when they get home.

The tests will be carried out by Clinical Physiology Technicians. The results will be interpreted by a Consultant Electrophysiologist. A report will be sent to the doctor who referred the patient.

Inflammation

• Tests that your doctor may order are a Magnetic Resonance Imaging (MRI) of the brain, a Lumbar Puncture to obtain cerebrospinal fluid, and blood tests to look for antibodies.

Compression

• Tests that your doctor may order are a Computed Tomography (CT) scan or MRI, and blood tests to determine the cause.
• Referral to an orbital surgeon or neurosurgeon may be necessary.

Raised intracranial pressure

• Tests that your doctor may order are a CT scan or MRI, which is usually necessary, together with a lumbar puncture to obtain cerebrospinal fluid for analysis.
• Referral to a neurologist or neurosurgeon is usually required.

The following are treatment options for some Neuro-Ophthalmic conditions.

Inflammation

• Treatment with steroids and/or other immunosuppressants may be required.

Ischemia

• Treatment is usually directed at controlling risk factors such as hypertension, diabetes, hyperlipidemia and smoking.