Research On Clinical Application Of Compensatory Head Position And Nystagmus Measurement With Children

Congenital idiopathic nystagmus（CIN）is the most common type of nystagmus in children clinically,affecting about 1 in 3,700.The main manifestations are visual dysfunction caused by nystagmus and abnormal head observation in children with nystagmus.The abnormal head position fixed in the child is called compensatory head position.A clinically effective treatment is to move the medial band of observation from the compensatory cephalic position to the emmetropephalic position by resuture of the tendon of the extraocular muscle.Therefore,quantitative and accurate measurement of compensated head position and intensity of nystagmus in children is of great significance for the treatment of this disease.However,existing measurement methods do not fully consider the needs of clinical measurement in children with CIN.In the measurement of head position,the accuracy and coordination of children were not taken into account,or the importance of the original head position in the measurement was ignored.Nystagmus measurement does not combine the characteristics of children nystagmus to realize the automatic analysis of nystagmus curve.In this paper,according to the clinical application requirements of congenital idiopathic nystagmus,we designed a measuring device that can simultaneously measure compensatory head position and nystagmus data.The head position measurement module is based on MEMS（Micro Electromechanical Syste）.IMU（Inertial Measurement Unit）angle sensor of mechanical Syste process can measure the head position in real time and accurately,with high degree of automation.Based on the eye video analysis of infrared camera,the nystagmus measurement module uses a processing method that first extracts the pupil region and then extracts the pupil center in each frame of eye image to accurately draw the nystagmus.The main work and research contents of this paper are divided into the following parts:（1）Design of compensatory head position and nystagmus device.The overall design of the mechanism refers to the mature wearable eye tracker on the market,which adopts a ball pair and a knob to adjust the camera position.At the same time,in view of the particularity of young CIN children,the headset design is adopted,which is comfortable,lightweight,adjustable in size,and inclusive to the needs of nystagmus children to wear glasses.（2）Study on compensatory head position measurement method.The relationship between screen coordinate system,head coordinate system and IMU Angle sensor coordinate system in the process of head position measurement is analyzed.In this paper,a method of determining the relationship between the IMU Angle sensor and the screen position was proposed,and then the original head position was determined by the IMU Angle sensor,so as to accurately measure the compensatory head position of children.（3）Study on measurement method of nystagmus.A new method based on BP（Back Propagation）neural network four-point calibration for eye position measurement was used to establish the fixation point mapping model of eye tracking.Compared with the traditional nine-point calibration method,the calibration process was greatly simplified.In the measurement of children’s nystagmus,both the cooperation of children and the accuracy of measurement were taken into care.According to the discontinuous and uneven characteristics of children’s nystagmus curves,the functions of locally magnifying the curves and moving the mouse to read the coordinates are realized on the nystagmus curves,and the nystagmus analysis is carried out on the continuous and uniform line segments.