Advancing the diagnosis of Dry Eye Syndrome : development of dynamic, automated tear film Break-Up assessment

[Resumen] El síndrome de ojo seco es un trastorno común de la película lagrimal que afecta a un sector significativo de la población, impactando en la calidad de vida. El diagnóstico de esta enfermedad es difícil debido a su etiología multifactorial, por lo que hay varias pruebas clínicas para evaluar diferentes aspectos de la película lagrimal. Una de las pruebas empleadas habitualmente es el test de BUT, que consiste en medir el tiempo transcurrido desde el último parpadeo hasta la ruptura de la película lagrimal, representada por la aparición de áreas oscuras que corresponden al adelgazamiento de la película lagrimal en la superficie ocular. Además del tiempo, hay varias características de la ruptura como la zona, la forma, el tamaño y la evolución, que podrían afectar a la severidad del síndrome de ojo seco. Sin embargo, el test de BUT presenta una baja repetibilidad debido principalmente a la apreciación subjetiva de los puntos oscuros, las diferencias entre expertos y la variabilidad de la película lagrimal. Además, la caracterización a mano de las zonas de ruptura es una tarea tediosa que consume mucho tiempo. La automatización del análisis de la ruptura reduciría su carácter subjetivo, permitiendo una evaluación más precisa de la película lagrimal. Este trabajo presenta una metodología novel para una evaluación de la ruptura de la película lagrimal totalmente automática. Este estudio permite un análisis cuantitativo y cualitativo de la inestabilidad de la película lagrimal como una extensi´on de la medida de BUT, que se centra solo en el tiempo. Esta metodolog´ıa proporciona resultados de precisión en los mismos rangos que entre los propios expertos. Así, la evaluación automática de la ruptura ahorra tiempo a los expertos proporcionando resultados imparciales que no están afectados por factores subjetivos.Resumo O síndrome de ollo seco é un trastorno común da película lacrimal que afecta a un sector significativo da poboación, impactando na calidade de vida. A diagnose desta enfermidade é difícil debido a súa etioloxía multifactorial, polo que hai varias probas clínicas para avaliar diferentes aspectos da película lacrimal. Unha das probas empregadas habitualmente é o test de BUT (Break-Up Time), que consiste en medir o tempo transcorrido dende o último pestanexo ata a ruptura da película lacrimal, representada pola aparición de áreas escuras que corresponden ó adelgazamento da película lacrimal na superficie ocular. Ademais do tempo, hai varias características da ruptura como a zona, forma, tamaño e evolución, que poderían afectar á severidade do síndrome de ollo seco. Sen embargo, o test de BUT presenta unha baixa repetibilidade debido principalmente á apreciación subxectiva dos puntos escuros, ás diferencias entre expertos e á variabilidade da película lacrimal. Ademais, a caracterización á man das zonas de ruptura é unha tarefa tediosa que consume moito tempo. A automatización da análise da ruptura reduciría o seu carácter subxectivo, permitindo unha avaliación máis precisa da película lacrimal. Este traballo presenta unha metodoloxía novel para unha avaliación da ruptura da película lacrimal totalmente automática. Este estudo permite unha análise cualitativa e cuantitativa da inestabilidade da película lacrimal como unha extensión da medida de BUT, que se centra só no tempo. Esta metodoloxía proporciona resultados de precisión nos mesmos rangos que entre os propios expertos. Deste xeito, a avaliación automática da ruptura aforra tempo ós expertos proporcionando resultados imparciais que non están afectados por factores subxectivos.[Abstract] Dry Eye Syndrome (DES) is a common disorder of the tear film which affects a significant sector of the population, impacting on quality of life. The diagnosis of this condition is difficult due to its multifactorial etiology, so there are a wide number of tests to evaluate different aspects of the tear film. Among the different tests available, the Break-up Time test (BUT) is a widely used measure to evaluate the quality and stability of the tear film on the ocular surface. It consists in measuring the time elapsed since the last blink until the tear film break-up, that is, the appearance of dark areas related to a thinning of the tear film on the surface of the eye. Besides the time, there are several break-up features such as the location, shape, size and dynamics of the breakup areas, which could affect to dry eye severity. However, the BUT test is affected by low repeatability mainly due to a subjective appreciation of the dark spots, the differences among the experts, and the variability of the tear film. Furthermore, the characterization by hand of break-up areas is a tedious and time consuming task. The automation of the break-up assessment would reduce its subjective character, allowing a more accurate evaluation of tear film stability. This work presents a novel methodology for a fully automatic assessment of the tear film break-up. The proposed methodology allows a quantitative, qualitative analysis of tear film instability, as an extension of BUT measurement, which is focused only on time. It provides accuracy results that are in the same ranges as the experts themselves. Therefore, the automated breakup assessment saves time for experts providing unbiased results which are not affected by subjective factors

Dynamics of the Tear Film

In this paper, current understanding of tear film physiology and mathematical models for some its dynamics are discussed. First, a brief introduction to the tear film and the ocular surface is given. Next, mathematical models for the tear film are discussed, with an emphasis on models that describe the formation and relaxation of the tear film from blinking. Finally, future issues in tear film modeling are listed

Automatic detection of fluorescein tear breakup sequence

Dry Eye Syndrome is a common disease in the western world, with effects from uncomfortable itchiness to permanent damage to the ocular surface. Almost 5 million Americans over 50 years old suffer from dry eye. A conservative estimate shows that approximately 17 million Americans have contact lens related dry eye -one of the main factors to contact lens discontinuation. In addition, the incidence of the disease is on the rise. Nevertheless, there is still no gold standard test that can reliably detect dry eye. One of the most commonly used tests by clinicians to detect dry eye is the Fluorescein Break Up Time (FBUT). However, results vary a lot between clinicians. Other tests such as observing the tear meniscus height are also performed regularly by the clinicians but not necessarily in conjunction with the FBUT test. Therefore there is a real need for a reliable, robust and operator-dependent method to evaluate dry eye. To our knowledge, no previous research has been conducted on automatic evaluation of dry eye in fluorescein images. In this thesis, we present new algorithms to automatically detect various dryness signs and make a number of original contributions. The first problem we address is how to detect the dry areas in fluorescein videos of the anterior of the eye, which are captured using a portable camera. We present a new multi-step algorithm which first locates the iris in each image in the video, then aligns the images according to the location of the iris and finally analyzes the aligned video to find the regions of dryness. We produce a novel segmentation result called dryness image, which depicts the various degrees of tear film thinning over the corneal surface. Then, we demonstrate through experiments that there is a large variation in the estimated Break Up Time (BUT) between clinicians and no ground-truth can be defined. To overcome that, we define a new value based on the clinical definitions of the BUT. These definitions are converted to image processing properties and an estimate of the BUT is computed using temporal analysis of the aligned video. We demonstrate that our new value is in the accepted range of the BUT values provided by the clinicians. We present an extension to the dryness algorithm, which is based on transforming the video to a volume by considering each video frame as a slice in a 3D volume. On a volume, a temporal monotonic constraint can be applied between pixels in consecutive slices. The constraint enforces the clinical definition of tear film thinning over time -the amount of fluid cannot increase while not blinking. The constraint is applied directly into the cost function and the whole volume is segmented simultaneously using graph-cuts. As a consequence, the approach is more robust and less sensitive to alignment errors. Finally, we generalize the idea and explain how monotonic constraints can be applied to other imaging modalities. In the last part of the thesis, we develop a new algorithm to evaluate the tear meniscus height and shape using graph-cuts. We formulate the segmentation problem using asymmetric cost functions and demonstrate its power and usefulness for the task. The asymmetry induces which directional moves are permitted in the minimization process and thus produces a result that adheres to the known shape properties of the tear meniscus. The iterative algorithm provides simultaneously the best segmentation result and shape prior of the meniscus

Determination of the burst initiation location and the tear propagation velocity during air burst testing of latex condoms

The stress testing of latex condoms by an air burst procedure has been slow in gaining industry acceptance because questions have been raised regarding the influence of the test apparatus on the likelihood of breakage occurring where the condom is attached to the inflation device. It was desired to locate the areas at which the condoms tend to burst and thus corroborate or disprove these claims. Several factors associated with the bursting condom demanded the use of special instrumentation to detect and study the burst initiation process. Microsecond duration electronic flashes were used for the initial stages of the investigation. Although the absolute point of initiation of a given burst could not be photographed, these high speed studies tend to indicate that the most likely place for high quality condoms to break is not where they are attached to the inflation device but at an intermediate area between the base and the tip of the condom. In addition, tear propagation characteristics and velocities were determined with a delayed-flash technique, a double-slit strip method and a rotating drum framing camera

The Ocular Surface Control of Blinking, Tearing and Sensation

Thesis (Ph.D.) - Indiana University, Optometry, 2014Dry eye is a common condition that affects millions in the US and worldwide. It is considered to be a multifactorial disease of the tear film and ocular surface and is associated with symptoms of ocular discomfort and visual disturbance. Low blink rate has been identified as a potential risk factor for the development of dry eye because it can result in increased evaporative loss from the tear film. Failure of tear secretion has also been recognized as one of the main factors for dry eye development, characterized as low tear volume and slow tear turnover rate. Both factors in turn may lead to increased tear film hyperosmolarity and instability, which are considered core mechanisms of dry eye. In the natural condition, the ocular surface is mainly protected by blinking and tear secretion in that the newly secreted tears flow into the upper and lower meniscus and the blink spreads the new tear film from the meniscus to the ocular surface. Therefore, the ocular surface control over blinking and tear secretion is important in the etiology of the dry eye condition. In this proposal, we develop a laboratory model using human subjects to test how input from the ocular surface affects both blinking and tear secretion. We hypothesize that ocular surface stimuli will activate corneal receptors to signal a high blink rate, reflex tear secretion and ocular sensations of discomfort. These probably act together for the purpose of preventing ocular damage. These results will help us to understand the manner in which the ocular surface responds to adverse stimuli, which may ultimately lead toward further development of treatments or methods in dry eye patients

Technological enhancements to optometric clinical tests

A sizeable amount of the testing in eye care, requires either the identification of targets such as letters to assess functional vision, or the subjective evaluation of imagery by an examiner. Computers can render a variety of different targets on their monitors and can be used to store and analyse ophthalmic images. However, existing computing hardware tends to be large, screen resolutions are often too low, and objective assessments of ophthalmic images unreliable. Recent advances in mobile computing hardware and computer-vision systems can be used to enhance clinical testing in optometry. High resolution touch screens embedded in mobile devices, can render targets at a wide variety of distances and can be used to record and respond to patient responses, automating testing methods. This has opened up new opportunities in computerised near vision testing. Equally, new image processing techniques can be used to increase the validity and reliability of objective computer vision systems. Three novel apps for assessing reading speed, contrast sensitivity and amplitude of accommodation were created by the author to demonstrate the potential of mobile computing to enhance clinical measurement. The reading speed app could present sentences effectively, control illumination and automate the testing procedure for reading speed assessment. Meanwhile the contrast sensitivity app made use of a bit stealing technique and swept frequency target, to rapidly assess a patient’s full contrast sensitivity function at both near and far distances. Finally, customised electronic hardware was created and interfaced to an app on a smartphone device to allow free space amplitude of accommodation measurement. A new geometrical model of the tear film and a ray tracing simulation of a Placido disc topographer were produced to provide insights on the effect of tear film breakdown on ophthalmic images. Furthermore, a new computer vision system, that used a novel eye-lash segmentation technique, was created to demonstrate the potential of computer vision systems for the clinical assessment of tear stability. Studies undertaken by the author to assess the validity and repeatability of the novel apps, found that their repeatability was comparable to, or better, than existing clinical methods for reading speed and contrast sensitivity assessment. Furthermore, the apps offered reduced examination times in comparison to their paper based equivalents. The reading speed and amplitude of accommodation apps correlated highly with existing methods of assessment supporting their validity. Their still remains questions over the validity of using a swept frequency sine-wave target to assess patient’s contrast sensitivity functions as no clinical test provides the range of spatial frequencies and contrasts, nor equivalent assessment at distance and near. A validation study of the new computer vision system found that the authors tear metric correlated better with existing subjective measures of tear film stability than those of a competing computer-vision system. However, repeatability was poor in comparison to the subjective measures due to eye lash interference. The new mobile apps, computer vision system, and studies outlined in this thesis provide further insight into the potential of applying mobile and image processing technology to enhance clinical testing by eye care professionals

Comparative Analysis of Nonpenetrating and Penetrating Abdominal Injuries

Trauma is an accidental or intentional injury caused by of energy which is usually mechanical in nature to a victim 1% of hospital admissions for trauma involve the Abdomen. Several abdominal injuries are common in patients with multiple injuries. Trauma to the abdomen are classified as PENETRATING and NONPENETRATING. While penetrating injuries are common in urban Places, nonpenetrating is common in civilian trauma victims. Damage to organs can occur in both penetrating and non-penetrating trauma. The sudden application of pressure in non penetrating trauma is more likely to rupture solid Organ. While penetrating trauma causes more injury to hallow viscus. Two major life threatening situations occur following organ injury in both penetrating and non-penetrating trauma are HAEMORRHAGE and HOLLOW VISCUS PERFORATION with associated chemical and bacterial peritonitis. AIM AND OBJECTIVES: To do a comparative observational study of organ injuries and sequalae in penetrating and non penetrating abdominal trauma patients admitting in trauma ward, Rajiv Gandhi Government General Hospital and emergency laparotomy done, in the following aspects. a. Single & Multiple Organ injuries-incidence, effects and sequalae. b. To know the various epidemiological factors related to trauma. c. To know the cause and mode of injury in organ injuries. d. Complications of various organ injuries. To determine the cause, presentation, anatomical distribution of abdominal trauma. MATERIALS AND METHODS: This comparative study was done in RGGGH CHENNAI during the period September 2015 to September 2016. 45 consecutive cases of abdominal trauma was chosen from this department, these 45 cases were classified into penetrating and non penetrating types according to the standard classification. All abdominal trauma patients were received by the Casualty Medical Officer (both MLC and non MLC) and these patients were admitted in Napier Ward, where the Duty Assistant Surgeon attended the patients. Resuscitative measures and the baseline investigations were done simultaneously. Careful history was elicited from the patients, if consciousness was altered, history was elicited from the attender of the patient. Thorough clinical examination was done. Age, Sex, IP No, mode of injury were noted. General examination of the patient was carried out. Pallor and hydration looked for in particular. On gross examination head injury, fracture ribs, fracture longbones or Pelvic fracture were looked for. A thorough abdominal examination was done. External bruise or abrasion were noted in particular for non penetrating trauma. In case of penetrating trauma, external wounds, evidence of peritoneal penetration, evisceration of omentum or viscera were noted. Signs of peritonitis or internal haemorrhage was looked for and noted in both types of abdominal trauma. Serial abdominal girth measurements, half hourly pulse, temperature, respiration and hourly BP chart were maintained in relevant cases. Base line blood investigations and radiological examination done in all cases. Tetanus Toxoid was given to all patients. All cases were given antibiotics parenterally. Diagnostic peritoneal tap was done in relavant cases. CONCLUSION: The following conclusions were drawn from this study; • Non penetrating trauma is more common than penetrating trauma. • Solid organ injury is common in Non Penetrating Trauma. • Hollow viscus injury is common in Penetrating Trauma. • Spleen is the commonest organ affected in Non Penetrating Trauma. • Liver injuries in this study are not very serious and they are treatable. Extensive liver injuries are potentially dangerous. • Hollow viscus like jejunum.ileum, colon, stomach are the common organs affected in penetrating trauma • Mortality and morbidity depends on delay in treatment, number of organs affected, number of injuries in each organ and which organ is affected. • Omentum is commonest structure to be prolapsed in wound site in penetrating trauma. • Bladder is the common organ associated with pelvic bone fractures. • wound infection is the common complication in the penetrating trauma

Investigation of Kevlar fabric based materials for use with inflatable structures

Design, manufacture and testing of laminated and coated composite materials incorporating a structural matrix of Kevlar are reported in detail. The practicality of using Kevlar in aerostat materials is demonstrated and data are provided on practical weaves, lamination and coating particulars, rigidity, strength, weight, elastic coefficients, abrasion resistance, crease effects, peel strength, blocking tendencies, helium permeability, and fabrication techniques. Properties of the Kevlar based materials are compared with conventional, Dacron reinforced counterparts. A comprehensive test and qualification program is discussed and quantitative biaxial tensile and shear test data are provided. The investigation shows that single ply laminates of Kevlar and plastic films offer significant strength to weight improvements, are less permeable than two ply coated materials, but have a lower flex life

Investigation of fluorine-based release agents for structural adhesive bonding of carbon fibre reinforced plastics

Abstract Peel plies can be used during the manufacture of fibre-reinforced plastics for two reasons: to protect the surface during transport and storing the parts as well as during subsequent work steps, such as adhesive bonding, the removal of the peel ply can result in bondable surface with required surface characteristics. However, the use of peel plies is not straightforward. It can be difficult to remove peel plies and a surface produced by a peel ply is altered in terms of roughness and elemental composition. In the present work, the influence of fluorine-based release agents on adhesive joining of carbon fibre reinforced composites is investigated. Within the scope of the screening, 14 fluorine-based release agents—ETFE release films, PTFE coated glass fabrics as well as fabrics made of PTFE fibres—were investigated. Preliminary studies (Meer, in: Deutscher Luft- und Raumfahrtkongress 2014, Augsburg, 2015) have shown that ETFE films have advantages in terms of adhesion. The study covers a number of aspects: the determination of the tear strength of the release agent by peel test; the determination of the element composition (XPS) and surface characteristics (SEM) before and after atmospheric pressure plasma pre-treatment, characterization the topology and the characterization of the adhesive strength by centrifugal adhesion test

Pneumatic Tire

For many years, tire engineers relied on the monograph, \u27Mechanics of Pneumatic Tires\u27, for detailed information about the principles of tire design and use. Published originally by the National Bureau of Standards, U.S. Department of Commerce, in 1971, and a later (1981) edition by the National Highway Traffic Safety Administration (NHTSA), U.S. Department of Transportation, it has long been out of print. No textbook or monograph of comparable range and depth has appeared since. While many chapters of the two editions contain authoritative reviews that are still relevant today, they were prepared in an era when bias ply and belted-bias tires were in widespread use in the United States and thus did not deal in a comprehensive way with more recent tire technology, notably the radial constructions now adopted nearly universally. In 2002, it was preposed that NHTSA should sponsor and publish electronically a new book on passenger tires, under editorship of the University of Akron, to meet the needs of a new generation of tire scientists, engineers, designers, and users. This text is the outcome. The chapter authors are recognized authorities in tire science and technology. They have prepared scholarly and up-to-date reviews of the various aspects of passenger car tire design, construction and use, and included test questions in many instances, so that the book can be used for self-study or as a teaching text by engineers and others entering the tire industry