Mosaicking and enhancement of slit lamp biomicroscopic fundus images

AIMS: To process video slit lamp biomicroscopic fundus image sequences in order to generate wide field, high quality fundus image montages which might be suitable for photodocumentation. METHODS: Slit lamp biomicroscopic fundus examination was performed on human volunteers with a contact or non-contact lens. A stock, charge coupled device camera permitted image capture and storage of the image sequence at 30 frames per second. Acquisition time was approximately 30 seconds. Individual slit lamp biomicroscope fundus image frames were aligned and blended with custom developed software. RESULTS: The developed algorithms allowed for highly accurate alignment and blending of partially overlapping slit lamp biomicroscopic fundus images to generate a seamless, high quality, wide field montage. CONCLUSIONS: Video image acquisition and processing algorithms allow for mosaicking and enhancement of slit lamp biomicroscopic fundus images. The improved quality and wide field of view may confer suitability for inexpensive, real time photodocumentation of disc and macular abnormalities.     

Routine biomicroscopy: A protocol for routine examination of the anterior segment of the eye and the ocular adnexa.

While the slit lamp biomicroscope has become an indispensable tool in contact lens practice, its use in the routine evaluation of the anterior segment may not be universal. The aim of this paper is to encourage routine use of the slit lamp. This paper does not detail methods of examining specific structures or describe types of illumination, however the protocol described provides students and practitioners with a framework on which a routine for external eye examination can be built.     

Grading nuclear cataract: reproducibility and validity of a new method.

AIMS: To assess the reproducibility and validity of a new instrument for grading nuclear cataract-the laser slit lamp, by comparison with an established method of lens grading-the Lens Opacities Classification System III (LOCS III). METHODS: 62 volunteers (113 eyes) were examined on two occasions. At each visit, a video image of the anterior segment was captured with the laser slit lamp and stored digitally. A measure of lens opacity for each laser slit lamp image was calculated using image analysis software. Each lens was also photographed on both visits for LOCS III grading of nuclear colour and nuclear opalescence. RESULTS: There was a linear increasing relation between the laser slit lamp measure of nuclear lens opacity and the LOCS III nuclear opalescence scores. The overall reproducibility of the laser slit lamp measurement was comparable with LOCS III (intraclass correlation coefficient of 95% (95% CI 92.9-96.5) for the laser slit lamp method; 97% (95% CI 95. 6-97.9) for the LOCS III method). However, among healthy subjects, the reproducibility was lower (intraclass correlation for the laser slit lamp of 38.6% (95% CI 12.9-59.2) and 76.1% (95% CI 62.3-85.4) for LOCS III. CONCLUSION: The laser slit lamp appears to give a valid measurement of nuclear cataract. The reproducibility of the instrument was high and similar to that of LOCS III. Modifications to the design would have to be made to improve its reproducibility among healthy subjects. It is simpler than other objective instruments, and could be useful in large scale studies of cataract.     

Video equipment recommendations for slit lamp videography.

Current developments in video technology have made videotaping through a slit lamp a useful capability available at a more reasonable cost. The technical basis of equipment needed to select or design an apparatus for slit lamp videography is reviewed. As an overview, the optimum slit lamp video apparatus would have the following criteria; the slit lamp should have zoom optics and rheostat illumination, the beam splitter should be a mirror or 70/30 type, the camera should have maximal light sensitivity (101ux) with reasonable resolution (greater than 300 lines). The recorder should be SP-Umatic or Super VHS for documentation, or consumer VHS for patient education, and the monitor should be a professional 13- or 15-inch monitor.     

Use of photographic techniques to grade nuclear cataracts

Methods for objectively documenting and grading different varieties of lens opacities are needed in order to conduct research on risk factors for cataracts. This study tested the feasibility and reliability of using two different photographic methods to grade nuclear opacities. Photographs were taken of 41 eyes using a regular Topcon SL-5D photo slit lamp, and using a Topcon SL-45 (Scheimpflug) camera. The photographs were graded against a set of four standard photographs of increasing nuclear opacification. Densitometric analyses were also performed on both sets of photographs. The clinical grade, on examination, of the nucleus was compared to the examiner's grade of each photograph. Agreement was fair between the examination results and the grading of the photographs. Inter-observer reliability was high (kappa = 0.71) with photographs taken using the photo slit lamp. Moreover, the severity grading of the photographs showed a good correlation with the severity of opacity as determined by densitometric analyses. On the basis of these data, and on the field experience, the use of photographs of the nucleus obtained by photo slit lamp may be used in epidemiological surveys.     

An accessory fill-in flash for the Nikon photo-slit lamp.

High-quality slit lamp photographs require a balance between slit beam exposure and exposure of surrounding ocular structures. Proper exposure of surrounding ocular structure is difficult to obtain with the Nikon photo-slit lamp. The purpose of this research was to design an accessory fill-in flash for this slit lamp, which would provide proper exposure of over all ocular structures. In addition, this paper describes the procedures used to obtain proper exposure values and provides an exposure table for this accessory flash unit.     

Automated, real time extraction of fundus images from slit lamp fundus biomicroscope video image sequences

AIMS: Slit lamp fundus biomicroscopy allows for high magnification, stereoscopic diagnosis, and treatment of macular diseases. Variable contrast, narrow field of view, and specular reflections arising from the cornea, sclera, and examining lens reduce image quality; these images are of limited clinical utility for diagnosis, treatment planning, and photodocumentation when compared with fundus camera images. Algorithms are being developed to segment fundus imagery from slit lamp biomicroscopic video image sequences in order to improve clinical utility. METHODS: Video fundus image sequences of human volunteers were acquired with a video equipped, Nikon NS-1V slit lamp biomicroscope. Custom developed software identified specular reflections based on brightness and colour content, and extracted the illuminated fundus image based on colour image analysis and size constraints. RESULTS: In five subjects with variable image quality, the approach allowed for automatic, robust, accurate extraction of that portion of the video image corresponding to the illuminated portion of the fundus. Non-real time analysis allowed for fundus image segmentation for each frame of the image sequence. In real time, segmentation occurs at 2 Hz, and improvements are being implemented for video rate performance. CONCLUSIONS: Computer vision algorithms allow for real time extraction of fundus imagery from marginal quality, slit lamp fundus biomicroscope image sequences.     

Relationship between precorneal retention of viscous eye drops and tear fluid composition

The influence of viscolysers on the precorneal residence of a fluorescent tracer was determined, using slit lamp fluorophotometry. The solution acceptability was evaluated by the volunteers by answering a standard questionnaire.The relationship between precorneal retention of viscous eye drops, discomfort and tear fluid composition after instillation of various cellulosic solutions was examined. Irritating hydroxypropylcellulose solution increases the total protein concentration of tears, without change in the ratio of lysozyme to total protein.Abbreviations HEC hydroxyethylcellulose - HPC hydroxypropylcellulose - HPMC hydroxypropyl-methylcellulose     

干眼症患者临床特征分析119例

目的 分析干眼症患者的主要临床症状和体征,探讨传统的检查方法对干眼症的诊断价值.方法 对有眼干等眼部不适症状为主诉的119例干眼症患者进行问卷式调查(包括8种症状:视疲劳、异物感、干涩、烧灼感、眼胀、眼痛、畏光、眼红),并进行Schirmer试验、泪膜破裂时间(break-up time,BUT)试验、角膜荧光染色和睑板腺检查4项检查.结果 在问卷的8种症状中,占前3位的是:眼干涩(70.1%)、视疲劳(67.0%)、异物感(55.6%).在临床检查中BUT试验的阳性率最高,为81.5%,其余3项检查的阳性率明显低于BUT.结论 干眼症的临床症状中以干涩、视疲劳、异物感为主,临床检查中BUT的阳性率最高,可作为干眼症的主要检查方法.     

智能手机图像采集在眼科住院医师规范化培训教学实践中的应用

目的：探讨智能手机自带的图像及视频采集功能配合裂隙灯检查在眼科住院医师规范化培训教学中的应用。

方法：利用手机支架将智能手机与裂隙灯显微镜一侧目镜相连接,通过调节裂隙灯光带配合前置镜、三面镜、房角镜的使用获取清晰图片或动态视频,然后在教学活动中使用无线局域网络连接、微信等软件,将影像资料传输给眼科规范化培训医师进行学习与交流,考核评价教学效果。

结果：智能手机图像采集功能配合裂隙灯检查所获得的照片及动态视频能够清晰地显示眼部组织及病变特点; 影像资料的快捷传输可以让更多的学生同时受到教育,及时互相交流; 与传统裂隙灯检查教学方式相比很大程度上提高了规培生的学习兴趣、学习参与度及学习效率。

结论：手机支架购买方便,简单易得,高像素的智能手机普及广泛,成像质量完全可以满足临床教学需要且丰富了临床教学资源; 智能手机图像采集功能配合裂隙灯检查在眼科住院医师规范化培训教学实践中值得推广。     

Darkfield biomicrography of eye bank donor corneas

PURPOSE: Evaluation of donated corneal tissue for transplantation relies on visual inspection by slit lamp biomicroscopy and specular micrography at the eye bank and then slit lamp biomicroscopy by the transplanting surgeon. An overall grade of tissue quality is assigned, but endpoints for biomicroscopic assessment are not universally accepted. We investigated the application of darkfield illumination to evaluate corneal transparency and provide a more standardized and reproducible method of tissue examination. METHODS: We built a fixture to securely hold a standard cornea storage container, and used two versions of photographic slit lamp biomicroscopes to examine donated corneal tissue with darkfield illumination. RESULTS: In every cornea we examined, darkfield illumination portrayed increased subject detail as compared with conventional methods of biomicroscopy. The epithelium appeared as a richly textured "ground-glass" field. We noted variations in transparency that could not be detected with conventional slit lamp biomicroscopy. The actual surface area of lesions such as cornea verticillata and herpetic dendrites appeared larger in darkfield illumination because of its high sensitivity to subtle alterations of transparency. CONCLUSION: Darkfield biomicrography of donated corneal tissue permits evaluation of the entire surface area, measurement of localized lesions of varying brightness, and assessment of epithelial cell coverage. As such, it extends our understanding of tissue clarity. Coupled with digital imaging technology, darkfield biomicrographs could be shared on the Internet and would allow transplanting surgeons to review tissue before selecting it for surgery. This technique could also be used in pharmaceutical research to measure changes in lesion size after therapy and could be incorporated into an eye bank quality assurance program. A new challenge for eye banking is to identify corneas in vitro that have undergone refractive surgeries such as laser in situ keratomileusis and photorefractive keratectomy-surgical alterations not easily seen at the slit lamp. Darkfield biomicrography may also be useful in detecting these lesions.     

Conversion of lens slit lamp photographs into physical light-scattering units.

PURPOSE: To derive from lens slit lamp photographs by means of densitometry the physically defined quantity for light scattering (the Rayleigh ratio) and to expand the use of the Lens Opacity Classification System (LOCS III) to include clear lenses and also to calibrate the LOCS III Nuclear Opacity (NO) score in physical terms. METHODS: Series of slit lamp photographs were taken from 38 eyes from 29 subjects (age range 18 to 84 years old) including cataracts, for 0.1- and 0.2-mm slit width, using 200 ASA and 1600 ASA film speed (Kodak professional; Eastman Kodak, Rochester, NY) and different flash settings with a Topcon SL-6E (12 slit/speed/flash combinations; Paramus, NJ). Additionally 19 eyes were photographed with a Zeiss 40 SL/P (8 slit/speed/flash combinations; Carl Zeiss, Thornwood, NY). A calibrated suspension of latex spheres also was photographed at the same 20 conditions. Densitometry was performed on the nuclear area of all photographs including the LOCS III standards, using a photometrically corrected photocell. Slit width and flash intensity settings were photometrically calibrated. All eyes and the suspension were digitally "photographed" with the EAS-1000 (Nidek, Gamagori, Japan) Scheimpflug system. RESULTS: For each eye and the suspension, the series of 20 or 12 densities, corresponding to a range of about 1 log unit in the amount of light used, proved to follow closely a course common to all eyes (the two film characteristics), apart from a shift in the amount of light (because of the differences in light back scattering). CONCLUSIONS: From normal slit lamp photographs, the physical quantity for light (back) scattering can be derived using transformation graphs derived in this study. The LOCS III NO score also can be used for clear lenses and translated into physical units. In this way, slit lamp photography can be used better for more precise studies, provided some minimal calibration of the photograph slit lamp.     

A case of secondary glaucoma studied by optical coherence tomography of the anterior ocular segment

PURPOSE: To compare slit lamp biomicroscopy or gonioscopy with optical coherence tomography (OCT) and to assess the efficacy of OCT in a case of anterior segment disease. CASE: A 74-year-old male who had bilateral keratoconus. The left eye was aphakic, and a penetrating keratoplasty was performed on it, as well as Nd:YAG laser capsulotomy. The prognosis was good in the early postoperative stage. But 6 months postoperatively, we could not control the intraocular pressure and judged that a second operation might be needed. Before the operation, we tried to get images of the anterior segment of this eye using slit lamp biomicroscopy, gonioscopy, and OCT. RESULTS: Findings obtained by OCT were more useful than those obtained by slit lamp biomicroscopy or gonioscopy to determine the method of operation. DISCUSSION: This case substantiates the view that observation of the anterior ocular segment by OCT is useful for such cases, because in cases of corneal disease we can not get much information about the deep and endothelial side of the cornea from slit lamp biomicroscopy.     

Shooting a film photo slit lamp into the digital age.

PURPOSE: The purpose of this study is to describe a method of taking a slit lamp initially designed for film photography and updating it to provide digital photographs. METHODS: A "how-to" guide is provided. RESULTS: Updating a Nikon FS-2 slit lamp is more economic than many practitioners may realize. By using what is already available on the market, a few steps can make a would-be dated instrument useful for many years to come. CONCLUSIONS: The upgrade to the Nikon FS-2 slit lamp is not only possible, but is able to functional well in the clinical setting and capture high-resolution photographs.     

Automated, computerized, feature-based phenotype analysis of slit lamp images of the mouse lens

Longitudinal studies of a variety of transgenic mouse models for lens development can create substantial challenges in database management and analysis. We report a novel, automated, feature-based informatics approach to screening lens phenotypes in a large database of slit lamp images. Digital slit lamp images of normal and abnormal lenses in eyes of wild type (wt), SC1 null and SPARC null transgenic mice were recorded for quantitative evaluation of their structural phenotype. The images were processed to improve the contrast of structural features that corresponded to rings of opacity and fluctuations in scattering intensity in the lenses. Measurable attributes were assigned to the features in the lens images and given as an output vector of 46 dimensions. Characteristic patterns were correlated with the structural phenotype of each mutant and wt lens and a statistical fit for each phenotype was defined. The genotype was identified correctly in nearly 85% of the slit lamp images on the basis of an automated computer analysis of the lens structural phenotype. The automated computer algorithm has the potential to evaluate a large database of slit lamp images and distinguish mouse genotypes on the basis of lens phenotypes objectively using a neural network analysis of the structural features observed in the slit lamp images. The neural network approach is a promising technology for objective evaluation of genotype/phenotype relationships based on structural features and light scattering in lenses. Further improvements in the automated method can be expected to simplify and increase the accuracy and efficiency of the feature based analysis of structural phenotypes linked to genetic variation.     

Slit lamp examination during COVID-19: Where should the protective barrier be?

Purpose:The aim of this study was to describe a poly-vinyl chloride air condition (PVC AC) curtain shield placed at the intervening space between the chin rest and the illuminating and optical arm of the slit lamp microscope (distal barrier) instead of the present position at the oculars (proximal barrier) to guard against severe acute respiratory syndrome Coronavirus 2. This experimental study was done to validate and compare the protection offered by the conventional breath shields and the one described by us in a simulated environment.Methods:In this experimental study, 12 puffs of fine mist were sprayed over a period of 1 minute using “magenta-colored dye” and “cyan-colored dye” for analyzing proximal barrier and distal barrier respectively. To access the amount of contamination of the slit lamp, caused by sprayed “magenta” and “cyan” colored dye, we covered the entire slit lamp with appropriately sized white-colored cotton sheet. The stained sheets were individually photographed and then the images were first cropped, then color threshold adjusted and then converted to binary and finally fraction of surface area stained was calculated using the ImageJ software. (P_n Surface Area_{magenta fraction} (%) during analysis of “proximal barrier” and P_n Surface Area_{cyan fraction} (%) during the analysis of “distal barrier”, where P_n refers to various parts of slit lamp.Results:The entire surface area of the cloth covering the slit lamp was 9912.45 cm². The surface area of the cloth which was stained when using the “proximal barrier” was 567.50 cm² whereas when using the “distal barrier” was 222.93 cm². When using proximal barrier, 97.71% of the staining was present on the slit lamp base, viewing arm, illumination arm and the pivot of the slit lamp. While using the distal breath shield no parts of the viewing arm, illumination arm, the pivot or the mechanical base with joystick were stained.Conclusion:The novel PVC AC curtain shield provides better barrier against the simulated contaminated stream of patient''s breath directed towards the working parts of the slit lamp as compared to conventional slit lamp oculars mounted breath shields.     

Measurement of the posterior corneal radius using slit lamp and Purkinje image techniques

A method for measuring the radius of the posterior corneal surface using the first and second Purkinje images has recently been developed. Values for the posterior corneal radius in the vertical meridian obtained using this method are compared with those obtained using a more conventional slit lamp method. A good correlation was found between values obtained using the two methods.     

VERION数字导航系统行散光矫正型人工晶状体（Toric IOL）轴位标记与传统裂隙灯标记方法的对比研究

目的　评价VERION数字导航系统行散光矫正型人工晶状体（Toric intraocular lens,Toric IOL）轴位标记的准确性和有效性。方法　回顾性分析2016年6月至2017年5月行白内障超声乳化摘出联合Toric IOL植入术的患者75例（75眼）,所有患者术前应用VERION数字导航系统采集眼前节图像并设定IOL预设植入轴位（目标轴位）,并于裂隙灯下采用1 mL注射器针头标记水平轴位。术中随机参考VERION导航下的IOL目标轴位或裂隙灯下标记的目标轴位植入IOL,记为VERION组（42眼）和裂隙灯组（33眼）,术后1 d、1周、1个月、3个月记录患者最佳矫正视力,散瞳后进行眼前节照相,应用Photoshop软件进行图像分析,比较两组患者术后不同时间点的最佳矫正视力以及IOL实际轴位与目标轴位的偏差值。结果　VERION组术后1 d、1周、1个月、3个月最佳矫正视力≥0.8的眼数所占比例分别为61.9%、78.6%、71.4%、76.2%,裂隙灯组分别为69.7%、78.8%、81.8%、75.8%,各时间点两组相比差异均无统计学意义（均为P>0.05）。VERION系统标记的IOL目标轴位与裂隙灯下针头标记的IOL目标轴位的差值为（3.04±1.99）°。两组患者术后不同时间点IOL实际轴位与目标轴位的偏差值均无统计学意义（均为P>0.05）。结论　应用VERION数字导航系统行Toric IOL轴位标记,术后效果准确稳定。     

30 SL/M-conception of a general utility instrument for ophthalmology (author's transl)

In respect to the instrument practice the slit lamp holds an eminent place in ophthalmology. The 6th generation of slit lamps after Gullstrand is now presented as a new development. The slit lamp 30 SL/M has been designed as a basic instrument which can be used with accessories to measure characteristics of the eye and to document actual shapes. With that the increasing demand for quantity and objectivity has been answered.     

裂隙灯显微镜对角膜内皮细胞形态观察的应用

目的：探讨裂隙灯显微镜镜面反光照射法对角膜内皮细胞形态观察的应用,以期指导临床诊断与治疗。方法选择2013年1月至6月就诊于我院,经非接触式角膜内皮细胞计数仪检查发现内皮细胞形态变异,数量减少至700个/mm2以下的患者10例和角膜内皮细胞数量及形态正常的健康者12例,对比裂隙灯显微镜镜面反光照射法与内皮细胞计数仪内皮照相两种方法观察内皮细胞形态的效果。结果所有患者利用裂隙灯显微镜（40倍）的镜面反光照射法均可拍摄到清晰的角膜内皮细胞。内皮细胞数量减少的患者,由于内皮细胞数量减少,直径变大,并可见融合变形细胞;对照角膜内皮计数仪检查可见细胞融合增大。同样用裂隙灯显微镜镜面反光照射方法观察正常人角膜内皮细胞,隐约可见细小六边形内皮细胞,内皮细胞数量越多,边界越难以清晰辨别。对照角膜内皮细胞计数仪可以得到同样的结果。裂隙灯显微镜放大倍数减少到16倍时,内皮细胞数量小于700个/mm2者仍可以观察到内皮细胞,但正常人的内皮细胞则无法分辨。结论利用裂隙灯显微镜镜面反光照射法对角膜内皮细胞形态及密度进行观察,是一种有效而快捷的临床技术。