| Purpose:After adjustment and improvement of the prototype, eye tracker is used to record saccades in normal subjects and nystagmus in congenital nystagmus patients simultaneously with EOG. This research aims to study the advantages of eye tracker in recording eye movement and the potentiality of its clinical application by analyzing and comparing waveforms recorded by the two methods.Methods:1. Adjustment and improvement of the prototypeNormal subjects put their submaxilla on the frame, and fixed at LED controlled by eye tracker software. Real-time image was observed on the monitor, from which whether the center of pupil and cross line of the image was in coincidence could be judged. The problems of software and hardware was checked and improved.. 2. Research on saccades in normal subjects by eye trackerAfter adaptation in lab for 10min, the normal subjects fixed at LED. Eye tracker software and EOG programme in Kanghua electrophysiologic equipment recorded saccades at each deflection angle (±5°,±10°,±15°,±20°) simultaneously for 15s. The jumping rhythm of saccades was 1 time per second. The waveforms and parameters were analyzed, while coefficient of variations in amplitude and data analyzing unit by two methods were in comparison.3. Research on nystagmus in congenital nystagmus patients by eye tracker After adaptation in lab for 10min, congenital nystagmus patients fixed at LED, whose eye movement was recorded by eye tracker software and EOG programme in Kanghua electrophysiologic equipment for 15s at each fixation point (-20°, -15°, -10°, -5°, 5°, 10°, 15°, 20°). Postoperative examination was performed two weeks after operation. The waveforms and parameters were analyzed, while the frequencies of nystagmus recorded by two methods were in comparison. The change of nystagmus after operation was also observed.Results:1. Adjustment and improvement of the prototypeAfter improvement of hardware and software, the system could pursuit eye movement stably and continuously. Judged subjectively, the center of pupil and cross line of the image was in coincidence. False identification disappeared, when eye moved to the peripheral position. Eye tracker had good qualities such as stability, utility, open, and higher precision.2. Research on saccades in normal subjects by eye tracker1) The waveform in EOG was in the form of sawtooth, but square in eye tracker. The mean value of data analyzing unit in both methods was rising along with the increasing absolute value of deflection angle as a'V'curve.2) Coefficient of variations in amplitude at each deflection angle were significantly lower in eye tracker group than that in EOG group( p<0.01 except at -10°p<0.05)3) Coefficient of variations in data analyzing unit were significantly lower in eye tracker group than those in EOG (p<0.01).3. Research on nystagmus in congenital nystagmus patients by eye tracker1) EOG was not sensitive when amplitude is under 40μv, which appeared as mixture with noise and leakage during recording, but eye tracker could record accurately.2) Except at 5°, 10°, the change of amplitude in eye tracker waveform had the same tendency with that simultaneous one in EOG waveform. There was no significant difference between frequency recorded by eye tracker and that simultaneously recorded by EOG.3) Analyzed nystagmus records in two cases pre-operatively and post-operatively. Record from eye tracker in subject 1 showed that amplitude decreased or almost remained the same after operation. However, EOG showed amplitude increased except at -5°, 0°, and 20°. The change of frequency after operation was not obvious. Because of the lower amplitude in subject 7, record from EOG could not be analyzed, while record from eye tracker presented the change of nystagmus well.Conclusions:1. After adjustment and improvement of the prototype of digital eye tracker, the system is convenient for operation with the advantages of non-contact, non-invasion, and small volume, which has good qualities such as stability, utility, open, and higher precision. 2. Under the same circumstances, using eye tracker to record saccades in normal subjects is less variable and more precise compared with EOG.3. The individual variation in record by eye tracker is less than that by EOG.4. EOG can not analyze nystagmus waveforms which amplitude is under 40μv , but eye tracker can record accurately for further analysis.5. Eye tracker can be used as an important objective method for assessing the degree of nystagmus and evaluating therapeutic efficacy in congenital nystagmus patients.
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