Abstract
A computer program was developed for on-line analysis of nystagmus parameters using a microcomputer (SORD M243EX). This computer has a Z80A microprocessor with a 320-kbyte random access memory, and includes two floppy disks with 2 megabytes of volume capable of storing application programs and analyzed data, as well as a graphic display and intelligent printer capable of displaying the results of analyzed data.In this system the programs consisted of two subprograms, ADCON, designed for analog-digital conversion and NYSANA for analysis of nystagmus. These subprograms were written in both BASIC and assembler language. When ADCON was run, the analog data of the eye positions obtained from electronystagmography were digitized at a rate of 100 samples/sec through the multi-channel of a 12-bit analog-digital converter, Digitized data were simultaneously monitored on the graphic display and stored in the main memory of the computer. Based on digitized data, quantitative analysis of each nystagmus parameter was achieved. The initial step in this algorithm was identification of the beginning and end points of the fast and slow phases of nystagmus. The velocity, amplitude and duration of the fast and slow phases of nystagmus were subsequently established.Thereafter, to distinguish differences between nystagmus and artifacts, such as eye blinks, three conditions were established as follows.1) The direction of induced fast phase of nystagmus must coincide with what is expected.2) The value of nystagmus parameter had to be within critical values which were based on the parameters of optokinetic nystagmus of 5 normal subjects and 5 patients with central nereous system disorders.3) The slopes of the fast and slow phases of nystagmus had to be regular enough to compute. Under these conditions, 98%, of nystagmus were identified precisely by the computer, and the reliability of this algorithm proved highly significant. From these results, the computer system in the present experiment was judged to be practical in routine clinical tests.
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