Research On Non-contact Intraocular Pressure Detection Technology Based On FPGA

IOP value is one of the important basis for doctors to diagnose glaucoma.Because of the poor measurement experience of contact tonometer and easy to cause cross infection,non-contact IOP detection becomes a more rapid,clean and comfortable measurement method,New hotspot in the field of intraocular pressure detection.In the United States,Japan and other developed countries,non-contact IOP detection technology has been relatively mature,and China still has problems with low accuracy and complex structure in this technology.Therefore,this paper proposes a high-precision,low-cost,Easy-to-use non-contact IOP detection technology.Based on the research of Imbert-Fick's law and related technologies of intraocular pressure detection,a detection scheme for flattening the cornea with airflow pulses to set the area and processing pressure data at the time of flattening was designed to achieve non-contact intraocular pressure detection.The overall plan is mainly divided into five parts: FPGA core unit,air jet realization unit,nozzle alignment unit,intraocular pressure signal detection unit and information interaction unit.FPGA core unit is responsible for the overall function control and signal processing.FPGA controls the airflow pulse to press the cornea out of a circular plane with a diameter of 3.06 mm,collects and processes the pressure value at the time of the flattening,and obtains the measurement results.The air jet realization unit provides The fluid pulses required to flatten the cornea are controlled by FPGA to control the rotary electromagnet to drive the jet device to complete the jet operation and adjust the jet volume.Compared with the traditional oil-free air compressor air supply device,the circuit is simple and the cost is low;The nozzle alignment unit determines the positional relationship between nozzle and cornea through the corneal position information.FPGA is used to control the movement of the three-dimensional stage to achieve the alignment of the nozzle with the center of the cornea.The intraocular pressure signal detection unit collects signals to complete the cornea during the jet.Detects pressure and deformation,obtains high-precision corneal applanation time data through FPGA peak-seeking algorithm,and combines the processed pressure data to obtain accurate intraocular pressure value;the information interaction unit realizes simple human-computer interaction through buttons and display screens and completes PC serial communication.An experimental analysis was performed on the technical indicators of IOP detection,and the feasibility of the scheme was verified.The experimental results show that the error of the intraocular pressure is|?P|?0.3kPa,and the repeatability R=0.056,which has reached the expected set index.Compared with current IOP detection accuracy and repeatability standards,both have improved,and are easy to use and lower in cost.