Purpose: To grade cataract changes in a Guatemala population with direct ophthalmoscopy and a grading system based on the grading system used by V. Mehra and D. C. Minassian in 1988. Methods: A population from Guatemala who attended field clinics conducted by Vision For All were included in this study. The sample consisted of 352 participants, 219 women and 133 men, from 9-90 years old. Mean age of the participants was 47.9 ± 17.8 years old. Binocular VA and subjective refraction was obtained with trial lenses and a Snellen E-chart at 5 meters. A 2 mm pinhole was used monocularly with the subjective refraction and whether participants felt any improvement in VA was documented.  The opacities in the red reflex in the crystalline lens were graded using a handheld direct ophthalmoscope. The grading was made in an angle of 25o nasal and at approximately 33 cm from the participant’s undilated eye. Results: The prevalence of cataract was 28.6% and 68% had some form of opacity in the red reflex. There was no statistically significant difference (p > 0.05) between the grade of lens opacities in right and left eye. Mean grade of lens opacities in right eye was 1.64 ± 1.46 and 1.63 ± 1.43 in left eye. The analysis showed a highly significant correlation between age and grade of lens opacities in right eye (y = 0.0657x -1.5106; r = 0.8; p < 0.001) and left eye (r = 0.78; p < 0.001). Lens opacities start to develop at an average age of 38.5 years in this population. There was a significant correlation between aided VA and grade of lens opacities for right eye (r = 0.52; p < 0.05) and left eye (r = 0.49; p < 0.05). 72 participants (20.5%) who had grading 3-5 in one or both eyes felt an improvement in their vision with the pinhole. Conclusions: The prevalence of cataract was 28.6% and this population had an earlier development of cataract compared to previous studies. This could be due to the UV-radiation, the temperature and nutrition and antioxidant insufficiency. Also this study showed a highly significant correlation between age and grade of lens opacities and a low, but significant, correlation between aided VA and grade of lens opacities.

The mechanism and the history of retinal photocoagulation are reviewed. The eye and the light beam parameters are discussed as they affect the coagulation lesion, and optimum parameters are indicated. Some comparisons are made between photocoagulators of various types. A new reason which may account for the unpredictability of the lesion size for a given exposure, the variable focal length or lens-to-retina distance of the eye, is suggested and studied. The use of a television ophthalmoscope for studying retinal coagulation generally, and in carrying out special studies in this thesis, is reported. Some unique haemorrhages and blast effects obtained during coagulation experiments are reported. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Thesis (M.S.)--Rochester Institute of Technology, 2005. / Typescript. Includes bibliographical references (leaves 54-56).

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第17826号 / 医博第3824号 / 新制||医||999(附属図書館) / 30641 / 京都大学大学院医学研究科医学専攻 / (主査)教授 渡邉 大, 教授 村井 俊哉, 教授 柳田 素子 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

<p>Optical coherence tomography (OCT) is a noninvasive three-dimensional interferometric imaging technique capable of achieving micrometer scale resolution. It is now a standard of care in ophthalmology, where it is used to improve the accuracy of early diagnosis, to better understand the source of pathophysiology, and to monitor disease progression and response to therapy. In particular, retinal imaging has been the most prevalent clinical application of OCT, but researchers and companies alike are developing OCT systems for cardiology, dermatology, dentistry, and many other medical and industrial applications. </p><p>Adaptive optics (AO) is a technique used to reduce monochromatic aberrations in optical instruments. It is used in astronomical telescopes, laser communications, high-power lasers, retinal imaging, optical fabrication and microscopy to improve system performance. Scanning laser ophthalmoscopy (SLO) is a noninvasive confocal imaging technique that produces high contrast two-dimensional retinal images. AO is combined with SLO (AOSLO) to compensate for the wavefront distortions caused by the optics of the eye, providing the ability to visualize the living retina with cellular resolution. AOSLO has shown great promise to advance the understanding of the etiology of retinal diseases on a cellular level.</p><p>Broadly, we endeavor to enhance the vision outcome of ophthalmic patients through improved diagnostics and personalized therapy. Toward this end, the objective of the work presented herein was the development of advanced techniques for increasing the imaging speed, reducing the form factor, and broadening the versatility of OCT and AOSLO. Despite our focus on applications in ophthalmology, the techniques developed could be applied to other medical and industrial applications. In this dissertation, a technique to quadruple the imaging speed of OCT was developed. This technique was demonstrated by imaging the retinas of healthy human subjects. A handheld, dual depth OCT system was developed. This system enabled sequential imaging of the anterior segment and retina of human eyes. Finally, handheld SLO/OCT systems were developed, culminating in the design of a handheld AOSLO system. This system has the potential to provide cellular level imaging of the human retina, resolving even the most densely packed foveal cones.</p> / Dissertation

Submitted by Filipe dos Santos (fsantos@pucsp.br) on 2018-04-03T11:16:04Z No. of bitstreams: 1 Jorge Enrique Mendoza Salcedo.pdf: 1111025 bytes, checksum: 0084f4a46fa4c16cbe04e36561f7628f (MD5) / Made available in DSpace on 2018-04-03T11:16:04Z (GMT). No. of bitstreams: 1 Jorge Enrique Mendoza Salcedo.pdf: 1111025 bytes, checksum: 0084f4a46fa4c16cbe04e36561f7628f (MD5) Previous issue date: 2018-02-23 / Introduction: The fundoscopy is part of the physical examination, being important in the diagnosis and prognosis of various pathologies. The teaching and learning of this technique, however, may become difficult if only patients are used for this purpose. Objective: Create a medical simulator of easy access and manufacture, to aid teaching the technique of direct fundoscopy. Materials and Methods: After testing several materials, we constructed an eye model using materials easily available on the internet. Plastic ball (pokeball); a slide transparency viewer; an inkjet printable transparency film. Result: We constructed a low-cost eye model, which can be used for teaching and training fundoscopy techniques. The model was tested during theoretical-practical classes to 10 physicians, who approved the model. Conclusion: Using simple and easy access materials, it is possible to construct models that help in the learning process of direct fundoscopy technique / Introdução: A fundoscopia constitui parte do exame físico e possui papel importante no diagnóstico e no prognóstico de diversas patologias. O ensino e o aprendizado da técnica, entretanto, podem ser mais difíceis, caso apenas pacientes sejam utilizados para aquele fim. Objetivo: Criar um simulador de fundo de olho, que seja acessível e cuja fabricação seja simples, a fim de auxiliar no ensino da técnica de fundoscopia direta. Material e Métodos: Após testar diversos materiais, construiu-se um modelo de olho humano por meio de utensílios acessíveis pela internet: uma bola de plástico (pokebola), um monóculo para transparência e um vinil adesivo transparente para impressora jato de tinta. Resultado: Criou-se um modelo de olho de baixo custo, que pode ser utilizado no ensino e no treinamento da técnica de fundoscopia. O modelo foi testado durante aula teórico-prática apresentada a 10 médicos, os quais aprovaram o modelo. Conclusão: Utilizando materiais simples e de fácil acesso, é possível construir modelos que auxiliam no processo de aprendizagem da técnica da fundoscopia direta

[Truncated abstract] Purpose: To improve our ability to interpret and validate Heidelberg Retina Flowmeter (HRF) flow images by recording flow measurements from specific regions of the retinal vasculature in in-vitro and in-vivo eye models in which retinal blood flow can be manipulated. Methods: The first experiments utilised an isolated perfused pig eyes perfused with a 50%/50% Krebs/RBC solution at known flow rates ranging from zero to 300 μl/min. After HRF image acquisition, the retinal vasculature was perfused with fluorescein isothiocyanate (FITC), for fluorescence microscopy. Using the standard HRF software and a 10×10 pixel measurement window, flow rates were measured from a retinal artery, vein, arteriole, venule, and the retinal capillary bed and a capillary-free-zone. The relationship between HRF measured flow and perfusion flow in the different measurement regions was determined. For the second study, HRF flow images were acquired at retinal sites in Brown Norway rats over a range of focus levels before and after cessation of retinal blood flow by laser-induced central retinal artery occlusion. Using the 10×10 pixel and 4×4 pixel measurement windows, HRF measured flow was performed in retinal artery, vein, arteriole, capillary and choroidal vessel locations. The relationship between HRF measured flow and focus depth was determined for each location before and after central retinal artery occlusion. At the conclusion of each experiment the effect of reduction of systemic blood pressure (by exsanguination) on HRF flow measurements in choroidal vessels and in locations without visible choroidal vessels was assessed. Finally, HRF flow measurements were acquired after euthanasia, to determine the HRF flow signal which was still present under zero biological flow conditions (the zerooffset). Results: In the isolated perfused pig eye experiments it was found that the HRF flow response varied according to vascular location. At zero perfusate flow, HRF flow was consistently greater than zero at all locations, averaging 171.9 ± 44.7 AU (n=97), representing background noise. Arteries and veins yielded the highest HRF measured flow values, but the relationship between HRF measured flow and perfusate flow was not linear. In arterioles the HRF flow was more linear over a broader range of perfusate flow rates but the peak flow signal was an order of magnitude smaller than that in arteries and veins. Both the linearity and magnitude of the flow signal in venules was less than that in arterioles.

Licentiatavhandling (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 2 uppsatser.

<p>Optical interrogation techniques are particularly well-suited for imaging tissue morphology, biological dynamics, and disease pathogenesis by providing noninvasive access to subcellular-resolution diagnostic information. State-of-the-art spectral domain optical coherence tomography (SDOCT) systems provide real-time optical biopsies of in vivo tissue, and have demonstrated clinical potential, particularly for applications in ophthalmology. </p><p>Recent advances in microscopy and endoscopy have led to improved resolution and compact optical designs, beyond those of conventional imaging systems. Application of encoded and multiplexed illumination and detection schemes may allow for the development of optical tools that surpass classical imaging limitations. Furthermore, complementary technologies can be combined to create multimodal optical imaging tools with advantages over current-generation systems. </p><p>In this dissertation, the development of coherence-gated and resolution-multiplexed technologies, aimed towards applications in human vitreoretinal imaging is described. Technology development in coherence-gated systems included increasing the imaging range of SDOCT by removing the complex conjugate artifact, improving acquisition speed using a scanning spectrometer design and a two-dimensional detector array, and hardware and algorithmic implementations that facilitated imaging of Doppler flow. </p><p>Structured illumination microscopy techniques were applied for resolution enhancement, and a spectrally encoded ophthalmic imaging system was developed for en face confocal fundus imaging through a single-mode fiber. These devices were resolution-multiplexed extensions of existing ophthalmic imaging devices, such as scanning laser ophthalmoscopes (SLO), which demonstrated improved resolution and more compact optical designs as compared to their conventional counterparts.</p><p>Finally, several multimodal ophthalmic diagnostic tools were developed that combined the advantages of OCT with existing imaging devices. These included a combined SLO-OCT system and a vitreoretinal surgical microscope combined with OCT. These devices allowed for concurrent ophthalmic imaging using complementary modalities for improved visualization and clinical utility.</p> / Dissertation

PURPOSE. Confocal laser scanning ophthalmoscopy (HRT; Heidelberg retinal tomograph II) and scanning laser polarimetry (GDx-variable corneal compensator [VCC]) were used to investigate whether early indicators of retinal nerve fiber layer (RNFL) thickness loss could be observed in patients infected with the human immunodeficiency virus (HIV) that had no associated retinopathy or optic neuropathy and were concomitantly receiving antiretroviral medications. METHODS. HRT and GDx-VCC parameters obtained from a group of 13 HIV-positive subjects (n = 26 eyes) on antiretroviral therapy examined with HRT, with a subgroup of six subjects (n = 12 eyes) examined with both HRT and GDx-VCC, were compared with those of a matched HIV-negative control cohort (13 subjects, n = 26 eyes) examined with HRT, with a subgroup of five subjects (n = 10 eyes) examined with both HRT and GDx-VCC. We employed generalized estimating equations for statistical analysis. RESULTS. Reduced mean values for the HRT height variation contour (p < 0.045) and HRT mean RNFL thickness (p < 0.023) were observed in HIV-positive subjects controlling for age, sex, and race. A significantly reduced mean value corresponding to the GDx-VCC superior maximum (p < 0.014) and inferior maximum (p < 0.016) were also observed for the HIV-positive cohort analyzed controlling for age, sex, and race. CONCLUSION. HRT and GDx-VCC indicators of RNFL thickness appear to be significantly reduced in HIV-positive subjects without retinopathy or optic nerve disease using antiretroviral medication, suggesting RNFL loss occurs in this population of HIV-positive patients. The lack of correlation between CD4 counts, viral load, number of antiretroviral medications used, or years from diagnosis of HIV and RNFL thinning, suggests that possibly other factors associated with HIV infection may contribute to the apparent RNFL thickness loss.