Design Of Multifocal Visual Electrophysiology Examining System

Clinical visual electrophysiology consists of electroretinogram (ERG), electrooculography(EOG); visual evoked potiential(VEP). It is a common method to test eye's function in ophthalmology. its features are objective and uninjured. The locality of illness can be finded in the pathway from all layersof retina to cerebral cortex by this method. According to its history of development, the techology of visual has three stages: traditional electrophysiology, local electrophysiology, multifocal electrophysiology. Multifocal visual electrophysiology examining system is designed by Erich.E.Sutter recently , which records retinal bioelectric response to light stimulus.He stimulated different retinal regions by graphics and ,at the same time ,recorded mixed signals of response by a common electrode. These signals are processed by a computer and signals of every retinal region , which reflect local retinal function, are abstracted. The amplitudes of these signals are displayed by 3D plot. The technology can analysis linear or non-linear components of the visual system. Through it we can acknowledge different layers of visual functions(such as sensitive cells of retina and ganglion cells).Our multifocal visual electrophysiology examining system simulates VERIS system. We have analyzed functions provided by VERIS system and basic principles of the system. We have divided the system into several modules and then designed each part seperately. Firstly, according to the definition pseudorandom binary m-sequence and fast m-transform' theory of Sutter, we have compiled arithmetic of C language. Secondly, we have implemented the function of graphic stimulating through multi-display technology which is owned by Windows 98 or Windows 2000 operating system. Because the signals exacted by the multi-focal visual electrophysiology examining system are very tiny. Their amplitude is from 50 nV to 700 nV. It demands amplifier very high. The paper introduces the electric circuit design of amplifier and choice of components. In order to make stimulating of graphy and collecting of data synchronize, we adopt data-collecting card which have FIFO. The multifocal visual electrophysiology examining system is strict with eye's fixation. So we design a monitoring system to monitor eye's fixation .Finally, we have three methods to display the examining effects of multifocal visual electrophysiology examining system: Traces, Grouping Traces, 3D-Plot. After we have completed the design of the system, we have carried on clinical tests for near four months. We have obtained the range of normal values of the system. We also have examined some patients. Its effects are consistent with the effects of VERIS4.0 system.