Visual electrodiagnostics

What we do in visual electrodiagnostics

We use sophisticated technology and methods to assess adults and children to provide a diagnosis for doctors in Newcastle Hospitals and across the region.

Our tests are ‘non-invasive’ investigations of the structure, function and performance of the visual system. Non-invasive means there is no penetration of the body by injection or incision.

We provide services to local hospitals across the northern region and to hospitals in the Yorkshire area.

Tests we carry out

We test the structure and function of the visual pathway – the link between the eyes and brain. Sensors are attached to the skin on the head or around the eyes to record tiny electrical signals that we produce when we look at our surroundings.

We use patterns on a TV screen or flashing lights to stimulate the eye to record these signals.

Visual testing

Each test takes about 30 minutes and the number of tests performed will depend on the patient’s needs.

These tests are performed to meet International Society for Clinical Electrophysiology of Vision standards.

As well as the standard investigations, we have a number of highly specialist advanced tests of retinal and optic nerve function to help us study the visual pathway in more detail.

Full field Electroretinogram (ERG)

We place sensors close to the eye to record the electrical signals produced by the eye in response to flashing lights. The first part of this test is carried out in the light, while the second part begins after a period of 15-20 minutes in the dark, allowing your eyes adapt. This enables us to record how the retina works in bright and dim light conditions. Your eyes will be dilated for this test using eye drops.

Multi-Focal Electroretinogram (mfERG)

We place sensors close to the eye to record the electrical signals produced by the eye in response to flashing patterns on a computer monitor. This gives us information about the centre of the retina – the macula. Your eyes will be dilated for this test using eye drops.

Pattern Electroretinogram (PERG)

We place sensors close to the eye to record the electrical signals produced by the eye while watching a moving checkerboard on a TV screen. This gives us information about the central retina (macula) and optic nerve.

Electro-oculogram (EOG)

This is a test of retinal function. Sensors are placed on the skin either side of each eye, and you will be asked to follow a moving light to make your eyes look right, then left for several seconds. This occurs every minute for 30 minutes. Your eyes may be dilated for this test.

Visual Evoked Potential (VEP)

This test records the brain waves which occur when you look at a moving pattern on a screen or at a flashing light. This provides information about the function of the optic nerves. The sensors are attached to the scalp using a simple adhesive paste which is easily removed after the test.

Services for children

We have very experienced technologists who can adapt the investigations to meet the needs and abilities of children. With their shorter attention span, we have developed interactive techniques to engage children while the tests are carried out. These include using bespoke equipment to maximize the information we gain from the investigations, while keeping the tests short and focused.

Children can bring their favourite music, story CDs or small toys – preferably noisy with no lights – to help us encourage children during the tests. Bringing a drink and snack along is also helpful.

Children perform these tests best when they are alert and happy rather than tired and irritable.

We have baby changing facilities in the unit.

Research and teaching

We are involved in a number of research and development programmes, and we have developed highly specialized equipment and methods for our research activities.

We have strong research links to the Newcastle Hospitals’ Ophthalmology Department, Paediatrics, and to Newcastle University.

We are also involved in teaching for technologists, vision scientists and junior doctors, and we run practical training in clinics and formal teaching sessions.