摘要
眼轴长度的精确测量对于近视防控、白内障晶体植入术后视力恢复等具有重要意义。本研究团队将Twyman-Green干涉系统与数字信号处理技术相结合,搭建了低相干双光束外差干涉眼轴长度测量系统。为验证该系统的有效性,采用该系统对ZEISS标准模拟眼、人眼分别进行多次测量,进行重复性检验;然后通过统计学分析测量数据的显著性,结果表明差异无统计学意义(P>0.05),符合球形检验;Bland-Altman分析表明,测量数据的95%一致性置信区间均在-0.06~0.06 mm范围内。本系统测量结果与IOLMaster500测量结果具有高度一致性。所设计的眼轴长度测量系统具有良好的有效性和可靠性,为国产眼轴长度测量仪器研发提供了技术方案。
Objective The prevalence of myopia in China remains high.Up to 50%of pupils and 90%of teenagers and young adults are myopic,and ametropia is increasingly affecting adolescents and highly educated groups.The development of human eyeballs and the refractive state of both eyes can be evaluated with reference to variation trends in axial length(AL).AL refers to the distance from the front-most surface of the cornea to the retinal pigment epithelium using the optical measurement method.Accurate measurement of eye-axis length is essential for myopia prevention and control and postcataract lens implantation vision recovery.In clinical practice,cataract,refractive error,strabismus,amblyopia,silicone oil-filled macular edema,and other diseases are accompanied by various changes in eye-axis length.Traditional A-or AB-ultrasound requires contact with the eye and is prone to cross-infection,and the measurement is dependent on the operator’s practical experience.Optical AL measurement has the advantages of no contact,high precision,and convenience.In this study,a new AL measurement system(New AL)was built based on an improved Twyman-Green interferometric system,which combines heterodyne interferometry and digital signal processing methods to achieve accurate measurement of AL at low cost,with a simple structure and flexible and convenient operation,providing a technical solution for domestic AL measurement.Methods A low-coherence dual-beam external differential interference ocular AL measurement system based on the Twyman-Green interferometric system was constructed using a 790 nm central wavelength and 30 nm bandwidth laser as the light source(Fig.1).The optical signal was converted to an electrical signal using aualanche photo diode(APD)and passed through the preprocessing circuit,which contained an amplified circuit and long-pass filter circuit.The preprocessing circuit was externally triggered by a data acquisition card(DAQ card)to be acquired as a digital signal,and both the interference signals peak position of anterior corneal surface and retinal pigment epithelium of the retina were detected and marked using digital processing methods.A band-pass filter finite impulse response(FIR)based was designed for signal filtering to abstract the Doppler shift of the optical signal;then,the peak marking of signals was obtained using Hilbert transform for envelope extraction(Fig.2).Finally,the optical length measurement of eye-axis length was obtained by reading the motion position of the reference mirror corresponding to the signal peaks from the anterior corneal surface and retinal pigment epithelium.The optical length was divided by the average refractive index of the eye tissue to obtain the geometric length of the eye axis(Fig.3).Statistical analysis of AL measurement data was conducted.The differences were not statistically significant according to Mauchly’s Test of Sphericity,conforming to the sphericity test and expressed using the mean±standard deviation.AL measurements were conducted using an IOL Master optical biometer and the New AL measurement system.The reproducibility of the devices was assessed using the intragroup correlation coefficient(ICC).AL measurements from both devices were analyzed for consistency using Bland-Altman analysis,and regression analysis was conducted to establish the mathematical relationship of AL values between the IOL Master and the New AL system.A value of P<0.05 indicates statistical significance.Results The team has completed the integration and engineering of the system,assembled on a 3D platform(Fig.4).Statistical analysis of the eye-axis measurement data was significant,and the differences were not statistically significant(P>0.05),following the spherical test;Bland-Altman analysis showed that their 95%confidence interval of the agreement was within-0.06-0.06 mm,indicating that the measurement data from the same operator had good repeatability,and ICC values>0.6 indicated that the signal data had a good agreement.The measurement results of this system are highly consistent with the results measured by IOLMaster500(Fig.5),which indicates that the ocular axis measurement of this system is accurate.Conclusions In this paper,we designed a dual-beam external differential interference eye-axis detection system with the Twyman-Green interferometric system architecture combined with digital signal processing technology to achieve low-coherence optical eye-axis length measurement.We implemented multiple measurements of the ZEISS standard analog eye axis and the human eye axis under the same conditions,the results showed that the eye-axis length measurement system designed in this paper had good validity and reliability.However,this system still had the error caused by the cooperation between the operator and the test subject during measurement,so we set the signal-to-noise ratio to>2.3 to ignore the interference of noise in the signal.In the next study,we will continue to optimize the signal processing method to improve the signal-to-noise ratio to enhance the accuracy of the measurements.This is necessary for accurate prediction of early pseudomyopia and myopia,their prevention and control,and to provide a technical solution for domestic AL measurement.
作者
王成
周岐
陈奕君
陈明惠
项华中
郑刚
赵婕
张大伟
Wang Cheng;Zhou Qi;Chen Yijun;Chen Minghui;Xiang Huazhong;Zheng Gang;Zhao Jie;Zhang Dawei(Institute of Biomedical Optics and Optometry,Key Lab of Medical Optical Technology and Instruments,Ministry of Education,University of Shanghai for Science and Technology,Shanghai 200093,China;Ophthalmology,Shayighai Yangpu District Shidong Hospital,Shanghai 200438,China;Key Laboratory of Modern Optical Systems,Engineering Research Center of Optical Instrument and System,Ministry of Education,University of Shanghai for Science and Technology,Shanghai 200093,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2022年第5期75-82,共8页
Chinese Journal of Lasers
基金
国家自然科学基金(61775140)。
作者简介
通信作者:王成,shhwangcheng@163.com。
