Relationship between the Alignment of a Non-Mydriatic Fundus Camera,Anterior Chamber Depth and Axial Length

Purpose:To evaluate the relationship between the position of the focal adjustment knob of a fundus camera and refractive error and biometric data as measured in the same eye.Methods:Normal eyes of patients presenting to clinics at the Beijing Tongren Hospital were examined with a non-mydriatic fundus camera.The position on the focal scale of a knob adjusting the distance between the camera lens and film plane,used to adjust focus the image of the patients fundus relative to the refractive power of the eye,was recorded in degrees.Ocular biometry and refractometry were performed on the same eyes.Results:The study included 136 subjects with a mean age of 36.5 ±19.6 years and a mean refractive error of-1.31 ±2.77 diopters.In univariate analysis,the position of the adjustment knob was significantly associated with refractive error.(P < 0.001;correlation coefficient r=-0.77),axial length.(P<0.001;r=0.65) and anterior chamber depth (P<0.001;r=0.48).After adjustment for age,anterior chamber depth decreased by 0.01 mm(95% confidence interval:0.003,0.017) for change per degree in the position of the adjustment knob.Conclusion:A fundus camera can be used to estimate anterior chamber depth,axial length and refractive error.In a screening setting,a fundus camera operated by a technician may be helpful to detect a shallow anterior chamber and evaluate a potential risk factor for primary angle closure.

Application of non-mydriatic fundus photography-assisted telemedicine in diabetic retinopathy screening

BACKGROUND Early screening and accurate staging of diabetic retinopathy(DR)can reduce blindness risk in type 2 diabetes patients.DR’s complex pathogenesis involves many factors,making ophthalmologist screening alone insufficient for prevention and treatment.Often,endocrinologists are the first to see diabetic patients and thus should screen for retinopathy for early intervention.AIM To explore the efficacy of non-mydriatic fundus photography(NMFP)-enhanced telemedicine in assessing DR and its various stages.METHODS This retrospective study incorporated findings from an analysis of 93 diabetic patients,examining both NMFP-assisted telemedicine and fundus fluorescein angiography(FFA).It focused on assessing the concordance in DR detection between these two methodologies.Additionally,receiver operating characteristic(ROC)curves were generated to determine the optimal sensitivity and specificity of NMFP-assisted telemedicine,using FFA outcomes as the standard benchmark.RESULTS In the context of DR diagnosis and staging,the kappa coefficients for NMFPassisted telemedicine and FFA were recorded at 0.775 and 0.689 respectively,indicating substantial intermethod agreement.Moreover,the NMFP-assisted telemedicine’s predictive accuracy for positive FFA outcomes,as denoted by the area under the ROC curve,was remarkably high at 0.955,within a confidence interval of 0.914 to 0.995 and a statistically significant P-value of less than 0.001.This predictive model exhibited a specificity of 100%,a sensitivity of 90.9%,and a Youden index of 0.909.CONCLUSION NMFP-assisted telemedicine represents a pragmatic,objective,and precise modality for fundus examination,particularly applicable in the context of endocrinology inpatient care and primary healthcare settings for diabetic patients.Its implementation in these scenarios is of paramount significance,enhancing the clinical accuracy in the diagnosis and therapeutic management of DR.This methodology not only streamlines patient evaluation but also contributes substantially to the optimization of clinical outcomes in DR management.

Evaluation of the Anterior Chamber Angle Structures in Perinatal Infants Using a Wide-Field Digital Fundus Camera

Objective This study aimed to evaluate the ability of a digital fundus camera to observe the development of the anterior chamber angle(ACA)in premature infants.Methods Forty-eight eyes of preterm infants(n=48)were examined by a digital fundus camera to observe the development of the ACA.ACA grading was performed based on the visualization of the anterior chamber structures according to the Scheie Angle Depth Evaluating System.Results ACA images from all 48 infants were successfully acquired using RetCam3.The corrected gestational age ranged from 30 weeks to 49 weeks,which covered the period from 2 months preterm to>2 months post-term.As the corrected gestational age increased,the corrected gestational age grading was significantly decreased.The mean corrected gestational ages of the infants corresponding to the ACA classification from grade IV to grade 0 were 32.75±1.89,37.20±1.30,39.75±2.38,40.56±2.24,and 44.23±2.14 weeks,respectively,which were all significantly different(P<0.05).The regression analysis showed a linear correlation between the grading of the ACA and the corrected gestational age(R2=0.724,P=0.0001).Conclusion The ACA of a full-term newborn can be fully detected and evaluated by a digital fundus camera.For premature infants,part of the ACA is not visible physiologically;however,it should not be misdiagnosed as angle closure or a narrow angle.

光学成像技术在早产儿视网膜病变筛查中的应用

早产儿视网膜病变(ROP)是一种视网膜血管增生性疾病,可能会导致患者视网膜脱离和永久性视力丧失。及时筛查和诊断ROP,并给予相应治疗,对于预防早产儿失明和降低致盲率至关重要。近年来,接触式和非接触式眼底照相机、荧光素眼底血管造影、光学相干断层扫描等光学技术的进步,极大地丰富了人们对ROP影像学特征的辨识能力。基于这些技术的发展,眼科专家们更新了ROP的影像学诊断标准。本文就光学成像技术在ROP筛查中的应用进行综述,以期为临床实践提供参考。

佳能CR-2型眼底照相机故障分析及解决方案

介绍了佳能CR-2型眼底照相机的工作原理和结构特点,分析了导致眼底照相机报故障码Err20、无法开机、图像有阴影等故障的原因,提出了快速有效的检修方法及处理方案,供同行参考和借鉴。

Feasibility of telemedicine program using a hand-held nonmydriatic retinal camera in Panama

AIM: To evaluate the image quality of a telemedicine screening program for retinal disease using a nonmydriatic camera among rural island communities in Bocas del Toro, Panama.METHODS: In June 2018, a group of three medical students volunteered at clinics operated by the Floating Doctors in the province of Bocas del Toro, Panama. Nonmydriatic images of the retina were obtained using the Pictor Plus(Volk Optical, Mentor OH), randomized, and sent to two board-certified ophthalmologists at the University of California, Irvine for analysis using a modified version of the FOTO-ED scale. Inter-rater reliability was calculated using the kappa statistic.RESULTS: Seventy patients provided a total of 127 images. Average image quality was 3.31, and most frequent image quality was 4/5 on the FOTO-ED scale. Thirty patients had at least one eye image with ideal quality(42.86%), while only one patient had no adequate photos taken(1.43%). However, high quality images were obtained in both eyes in only 12 patients(17.14%). The inter-rater reliability between the two ophthalmologists was 0.614.CONCLUSION: Further improvements are necessary to acquire higher quality images more reliably. This may include further training and experience or mydriasis.

Near-infrared fundus camera based on polarization switch in stray light elimination

This letter shows that the human eye fundus tissue has higher reflectivity at the near-infrared （NIR） wavelength, and that some aberrations exist at the pre-optical system from cornea to vitreous. We design a NIR fundus camera with inner focusing, which can be applied to the -10 D to 10 D range of vision and has the advantage of ensuring the stability of image when is focused. Considered as Liou＇s eye aberration model, we correct the integrated aberration to ensure a 100 lp/mm resolution when we complete the assembly and calibration of the fundus camera. Kohler illumination is also applied to obtain uniform fundus illumination. Moreover, we put forward a novel method for stray light elimination based on polarization switch, which inhibits ghost image formation near the focal plane when the illumination beam is reflected by the eyepiece surface. The result shows that this method is effective in ensuring an illumination uniformity of 80%, with the advantage of simple structure and easy assembly.

A GAN-based deep enhancer for quality enhancement of retinal images photographed by a handheld fundus camera

Objective:Due to limited imaging conditions,the quality of fundus images is often unsatisfactory,especially for images photographed by handheld fundus cameras.Here,we have developed an automated method based on combining two mirror-symmetric generative adversarial networks(GANs)for image enhancement.Methods:A total of 1047 retinal images were included.The raw images were enhanced by a GAN-based deep enhancer and another methods based on luminosity and contrast adjustment.All raw images and enhanced images were anonymously assessed and classified into 6 levels of quality classification by three experienced ophthalmologists.The quality classification and quality change of images were compared.In addition,imagedetailed reading results for the number of dubiously pathological fundi were also compared.Results:After GAN enhancement,42.9% of images increased their quality,37.5%remained stable,and 19.6%decreased.After excluding the images at the highest level(level 0)before enhancement,a large number(75.6%)of images showed an increase in quality classification,and only a minority(9.3%)showed a decrease.The GANenhanced method was superior for quality improvement over a luminosity and contrast adjustment method(P<0.001).In terms of image reading results,the consistency rate fluctuated from 86.6%to 95.6%,and for the specific disease subtypes,both discrepancy number and discrepancy rate were less than 15 and 15%,for two ophthalmologists.Conclusions:Learning the style of high-quality retinal images based on the proposed deep enhancer may be an effective way to improve the quality of retinal images photographed by handheld fundus cameras.

免散瞳眼底照相机的精密调焦

为实现免散瞳眼底相机在被观测眼底图像较暗情况下的精确调焦,提出了双光楔裂像调焦方法。采用该调焦方法,将一条矩形狭缝视标投影成像到视网膜上,在双光楔的作用下,通过矩形狭缝上下两半部的光线传播方向不同,根据上下两半条矩形狭缝在视网膜上所成像分离的方向和大小决定调焦的方向和调焦量的大小,将视网膜上两半条矩形狭缝像调焦到位于一条直线上。实验结果表明:相对于直接观测眼底细节进行调焦来说,双光楔裂像调焦方法能使调焦精度提高50度(0.5 m-1)以上。这种调焦方法具有精确度高、操作简单等优点。

折反式眼底相机光学系统设计

为控制传统眼底相机的杂光和鬼像,设计了一款40°视场、48mm工作距离的折反式眼底相机光学系统。设计了离轴反射式网膜物镜,引入了自由曲面以校正其离轴像差,成像物镜中采用两个自由曲面对网膜物镜的剩余像差进行校正。建立了一种离焦眼模型,用于优化成像光路,消除人眼像差对成像的影响,同时得到不同视度缺陷眼的成像光路。照明光路中使用3个相邻的环形光阑,减少了眼球光学系统反射的杂光。成像光学系统可在-10～+10m-1调焦,物方各视场分辨率为33lp/mm,系统畸变小于8.5%;照明光学系统在不产生鬼像的前提下,可均匀照明眼底,照度非均匀性在15%以内。实验表明,引入自由曲面的折反式眼底相机,有效地消除了杂光和鬼像,满足大视场和大工作距离的要求。

立体成像眼底相机光学系统设计

为了实现从不同角度同时拍摄同一眼底视网膜区域的图像,使采用双目立体视觉法进行眼底三维重建成为可能,设计了一种免散瞳立体成像眼底相机光学系统。该光学系统由成像系统和照明系统两部分组成,在成像系统中,使用Gullstrand-Le Grand眼模型来模拟正常人眼,运用体视显微镜成像原理进行分光设计;在照明系统中,通过设置黑点板的方式消除网膜物镜产生的杂散光,并加入环形光阑以避免角膜反射光的产生。设计结果表明,本立体成像眼底相机光学系统截止频率在95lp/mm处各视场的MTF值均大于0.2,成像系统畸变小于-3%,场曲值小于0.1mm,色差矫正良好,并且具有较强的调焦能力,能对-10^+5m^(-1)的人眼清晰成像。

免散瞳眼底照相技术在学龄前儿童眼底病筛查中的应用

目的:观察免散瞳眼底照相机在检查中所见的学龄前儿童眼底病变的发病情况,并与直接检影镜检查结果进行对比分析。方法:收集2012-04/2013-10来我院眼科门诊就诊的学龄前儿童3896例7760眼,采用日本Topcon TRC-NW300彩色荧光眼底照相机拍照,图像及时保存,并进行直接检影镜检查。结果:免散瞳眼底照相技术的检出率较直接检影镜高。3 896例7 760眼患儿中,检出41眼(1.05%)眼底异常者。其中视网膜有髓鞘神经纤维(24.39%)、牵牛花综合征(21.95%)、视网膜色素变性(14.63%)、先天性视网膜劈裂(12.20%);而儿童眼病非单一发生,常伴有视力异常(68.30%)、屈光异常(63.41%)、斜视(19.51%)。结论:免散瞳眼底照相技术具有不用药物散瞳,学龄前儿童易于接受,图像结果即刻显示,能够直观、清晰显示眼底各种病变,对学龄前儿童眼病筛查有重要意义。

眼底图像的三维重建

根据简化眼模型和眼底照相机光学系统简化模型建立了眼底图像三维重建的数学模型,分析了正常眼和屈光异常眼眼底图像与真实眼底视网膜形状的关系,导出了眼底二维平面图像到三维曲面图像的映射关系,最后给出了对眼底图像进行三维重建的实例。眼底三维重建图像的最大视场取决于眼底照相机的最大视场角,该最大视场角限制了重建图像的视场大小和三维重建时z轴的取值范围。根据给出的三维重建映射公式对眼底图像的二维数据进行三维映射后,再进行纹理映射,即可绘出重建后的三维眼底图像。该方法利用现有二维成像设备提供患者眼底三维重建图像,可为眼科医生在临床诊断和治疗时提供有益的参考和帮助。

基于眼模型的非球面眼底荧光相机的设计

运用非球面光学理论,设计了一款基于Gullstrand-Le Grand眼模型的便携式非球面眼底荧光相机。该相机根据滤光片选择原则,选用Nikon公司的B-2A滤光组合作为滤光系统进行光谱滤光;为避免角膜中心较大曲率引起的杂散光,采用环形光阑和共轴式照明相结合的照明方式实现眼底均匀照明;摄影系统中引入眼模型结构,综合校正了人眼及系统的像差,实现了全视场20×106pixel的高清晰成像。该摄影系统包含有2个非球面结构,使系统由9片镜结构简化为7片镜结构。实验结果表明,该相机具有较大的调节能力,对-12～+12m-1的人眼普遍适用,其视场角为30°,像面成像分辨率为120lp/mm,畸变值<3.9%。非球面光学元件的使用,有效地简化了系统,减小了系统体积和重量,提高了成像质量。

便携式免散瞳眼底相机光学系统设计（英文）

设计了一种便携式免散瞳眼底相机光学系统,达到了全视场300万像素的高清眼底成像。在考虑人眼生理特征和光学特性的基础上,引入Gullstrand-Le Grand眼模型来模拟被测屈光度正常的人眼,用Schematic眼模型来检验屈光度异常人眼对成像光路的影响。在成像系统中,首先采用接目物镜会聚从人眼视网膜反射出瞳孔的光线,然后再由成像物镜将视网膜的像成像到CCD上。在照明系统中,为避免角膜中心区域产生杂散光,采用环形光阑和共轴照明相结合的照明方式给眼底照明。仿真结果表明:该系统视场角为30°,成像分辨率高于120lp/mm,场曲值小于0.12mm,畸变仅为-1.2%,全视场色差值均在艾里斑之内,且该光学系统具有较大的调焦能力,对-10 D^+10 D的人眼普遍适用。所用的光学元件均为普通的球面玻璃,便于加工制造且能有效降低实际的制作成本。

遮挡条件下瞳孔精确检测方法

针对人眼图像的瞳孔提取中光源反光、睫毛、眼皮等干扰问题,提出了一种在眼皮部分遮挡下的瞳孔检测方法.该方法首先在瞳孔分割的基础上,通过滤波和扫描线法去除光源反光的影响.然后根据眼皮遮挡瞳孔的分界线进行旋转,利用内接平行四边形法确定瞳孔中心,通过五点法恢复出遮挡的瞳孔椭圆边界.实验结果表明,提出的方法在遮挡不超过瞳孔面积一半的情况下,能得到较为精确的瞳孔位置和边界,具有良好的鲁棒性和准确性.

眼底照相机图像采集与处理系统

眼底照相机图像采集与处理系统,采用具有RGB信号输出的高清晰CCD摄像头以及专用图像采集卡,快速高质量地完成眼底图像的采集工作,系统软件提供功能强大的病员数据库管理、图像处理功能以及丰富的辅助诊断病例库,可有效地为眼科医生对眼底疾病的诊断提供帮助。

免散瞳眼底照相对提高糖尿病患者治疗主动性的效果

目的探讨免散瞳眼底照相(NMFCS)对提高糖尿病患者治疗主动性的效果。方法采用NMFCS对2400例(4800只眼)糖尿病患者进行眼底检查,建立了完整的患者资料库,并对患者定期复诊。结果发现53%的患者存在不同程度的DR,42%的患者无任何不适的自觉症状。根据DR的临床分期,其中0级1128例,Ⅰ级534例,Ⅱ级381例,Ⅲ级294例,Ⅳ级27例,Ⅴ级24例,Ⅵ级12例。结论NMFCS简单易用,患者能直观的看到自己的眼部病变,特别对无眼部症状的患者能引起他们的足够重视,治疗主动性大大提高,能有效地预防并治疗糖尿病性视网膜病变。

眼底相机的均匀照明及消杂光干扰设计

给出了一种新型眼底相机照明系统的设计方案。针对现行眼底相机照明系统复杂的问题,对经典的柯勒照明光路进行改良设计,得到了一个结构简单的眼底照明系统。结构中除网膜物镜外,只需用到4片透镜,且眼底照明区域直径连续可调,充分利用了光能。通过在照明光路中添加黑点板和环形光阑,屏蔽了系统99%以上的杂散光,使眼底相机成像画面的信噪比达到20dB以上,提高了对比度。同时在Gullstrand_Le标准眼模型上,得到一个均匀度达95%以上的照明区域。

免散瞳眼底照相在眼底检查中的应用

目的分析研究免散瞳眼底照相在眼科眼底检查中的应用。方法对2030例本院（门诊及住院会诊）患者行免散瞳眼底照相检查和直接检眼镜检查，分析检查结果，研究免散瞳眼底照相方法检查眼底的应用选择。结果检出1316例眼底病变，其中视网膜动脉硬化421例（占31．99％），其次为高度近视眼底改变205例（占15．58％），以及糖尿病视网膜病变97例（占7．4％）。免散瞳眼底照相检查与直接检眼镜检查结果的一致性为99．7％。结论免散瞳眼底照相检查是一项操作简便、安全快捷、记录客观的眼底检查方法，适合作为眼科常规检查，早期发现眼底病变及全身性血管病变，广泛应用于指导眼底疾病的诊治及全身血管健康状况的评估。