The retina is like a screen at the back of the eye onto which the optics of the eye project an image of the outside world. Besides a layer of light-sensitive cells, it contains multiple layers of neurons that pre-process the image before the information is sent to the visual areas of the brain. When the eye is stimulated, for example, with a flash of light, small electrical responses can be derived either from the eye with special contact lenses or from the visual cortex with electrodes pasted to the scalp. These signals from the eye are called the electroretinogram, or ERG and the signals from the brain are called the visually evoked cortical potentials or VEP.

Our laboratory has developed and perfected techniques that permit mapping of these responses across the visual field. The new techniques are called multifocal ERG (mfERG) and multifocal VEP (mfVEP). They are now widely used in research and clinics. The technique is sensitive enough to map depressions due to the shadows cast by the retinal blood vessels on the light sensitive cell layer behind. With the mfERG, it is also possible to extract signal components originating from different retinal layers.

Diseases of the eye and the optic nerve, as well as systemic diseases affecting the retina, generally manifest themselves first by small dysfunctional areas in the patient's visual field. The ability to test retinal function locally and layer by layer often provides valuable information regarding the location and nature of pathological changes. The detection and mapping of affected areas by means of mfERG or the mfVEP techniques is important for diagnosis and disease management as well as for research into new methods of treatment.

Objective mapping of visual function by means of the new mfERG and mfVEP techniques has already proven itself in many clinical applications. Today, the instrumentation is found in hundreds of research laboratories and clinics around the world. Our own research is now focused on optimizing the multifocal stimulation and analysis for the detection and mapping of early changes in glaucoma, diabetes and diseases affecting the inner layers of the retina.

For more information, visit Erich Sutter's lab web pages.

Collaborators: John Hallisey, Jason Lee, Philip Penrose, Michael Menz, Momoyo Menz.