Development Of Four Points Perimeter Used For Screening Glaucoma Rapidly And Determination Of Normal Reference Value

ObjectiveGlaucoma is the most serious irreversible blinding eye disease in the world,and is difficult to be detected at an early stage.Many glaucoma patients already have severe optic nerve injury and visual field damage when first diagnosed.Moreover,early diagnosis is the key of treatment;widespread screening in crowds is one of the effective methods of detecting glaucoma early.Perimetry is an important way of accessing visual function changes in glaucoma.But usual perimeter is very time consuming and hard to carry,which cause the limitation of applying in mass screening glaucoma.Therefore,this paper developed rapid,effect,portable Four Points Perimeter to adapt the requirement of mass screening glaucoma.MethodsFour Points Perimeter is constituted of upper computer,lower computer and communication interface.Upper computer(PC) sends orders to lower computer(MCU),and analyzes the signals transmitted by MCU.MCU is used to control light change and detection sequence of LED in the visual field screen,and transmit the patients' response to PC.Data transmission is realized by serial communication between PC and MCU.The software design of MCU uses the C programming language,which includes main system program,interrupt disposing program,rapid screening subprogram,four points threshold test subprogram, keystroke query subprogram,communication subprogram and so on.The software of PC is designed based on VB6.0.The serial communication with MCU and the real time display of perimetry are achieved by setting MSComm serial port control;Using data binding control,we establish the database management system based on Access database as a background,then we can store,modify and query the patients' information and detected data.VB and VC programming languages combined to design the print module of inspection report.Four Points Perimeter choose 100 eyes' visual field of 50 normal person who conform to the selected standard to accept the test,they are categorized as 5 age sections,≤30 year old,31-40 year old,41-50 year old,51-60 year old,≥61 year old,each section have 10 person.They separately accept the static perimetry by testing the four points which appear abnormal most easily on visual field loss in glaucoma,using two test strategies of four points threshold test procedure in Four Points Perimeter.We obtain the normal reference value in various age sections after statistics processing of the results.ResultsThe sample device of Four Points Perimeter which is rapid and portable was completed.We can choose different procedure to control the display mod of LED,and change the brightness value of LED in the visual field screen according to subject's response,thereby to proceed with Four Points Perimetry.The system of Four Points Perimetry performed the function of interface display,patients' data management, inspection report printing,data transmission and disposal,real time display of test process and so on.By testing normal person mean sensitivity of four points with two test strategies of four points threshold procedure,the results manifested that MS of normal person had correlation with age,the older the lower MS.Average every 10 years old,MS reduced 1.319dB from strategyⅠ,MS was not completely same,the difference of MS between 30 year old section and 40 year old section was not significant(P＞0.05), there were significant difference in MS between other years old sections(P＜0.05); MS reduced 1.225dB from strategyⅡ,there were significant difference in MS between every years old sections(P＜0.05).The difference of MS between various age sections in male and female,in left eye and right eye were not significant(P＞0.05). The difference of MS between two test strategies was significant(t=4.513, P=0.000),MS from strategyⅠwas lower about 0.5dB than strategyⅡ.Moreover,the average testing time of less than 1 minute per eye using two test strategy decreased deeply compared with an average testing time of 12-20 minutes per eye.ConclusionsThe sample device of Four Points Perimeter has simple configuration,easy operation,and short testing time.Two test strategies of four points threshold procedure in Four Points Perimeter had established the normal reference value respectively in every age sections by testing visual field of normal person.The normal reference value's characteristic obtained by this experiment and the normal reference value's characteristic obtained by other type perimeters are basically concordance. Therefore the reference value provides the diagnosis basis for continuing clinical experiment.This paper on the development of Four Points Perimetry provides technique support for mass screening glaucoma.