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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Macular Pigment and Lens Optical Density Measurements-Evaluating a Flicker Machine with Novel Features

Mukherjee, Anirbaan 02 July 2015 (has links)
Age related macular degeneration (AMD) is one of the leading causes of blindness amongst the elderly. Macular pigment (MP) in the retina has been established to protect individuals against AMD. Improving levels of MP by diet or supplements is the constant quest of clinical practitioners and researchers, thus necessitating development of instruments capable of repeatable and reliable MP measurement. Cataract, a consequence of the rising opacity levels of the lens with age is one of the other major causes of blindness in the world. Mapcatsf, a LED-based microprocessor-controlled heterochromatic flicker photometer (HFP) using photopic vision is capable of measuring the levels of MP and the opacity of the lens in terms of optical density. Test-retest measurements conducted on 83 subjects were analyzed for repeatability in macular pigment optical density (MPOD) measurements. Reliability of the lens optical density (LOD) measurements were tested and compared with those obtained at absolute scotopic thresholds for 25 individuals. A supplement study with 32 individuals both in the young (50) age groups for 6 months further established Mapcatsf’s capacity to monitor changing levels of MP in individuals. As an overall outcome, high levels of repeatability and reliability were obtained in MPOD and LOD measurements establishing Mapcatsf as an instrument for use in clinical settings in the future.
2

Estudios electrorretinográficos en modelos de neurodegeneración en el sistema visual del roedor adulto

Alarcón Martínez, Luis 23 October 2009 (has links)
Las enfermedades neurodegenerativas cursan con la degeneración y muerte de las neuronas las cuales son incapaces de suplir su propia muerte. Debido a esta característica enfermedades como el Alzheimer, el Parkinson o el Glaucoma no tienen cura en la actualidad. La retina es una proyección del sistema nervioso central (SNC) encapsulada en el globo ocular y aislada del resto del SNC, lo que la hace fácilmente accesible a la manipulación experimental. En este trabajo estudiamos las alteraciones funcionales de la retina con el electrorretinograma de campo completo (ERG), técnica basada en el registro de la respuesta eléctrica retiniana tras la presentación de un estímulo de luz homogéneo. Así hemos estudiado los efectos de la sección del nervio, del aumento de presión intraocular y de la fototoxicidad, dichas lesiones afectan selectivamente a determinadas poblaciones neuronales retinianas e imitan enfermedades neurodegenerativas como el Glaucoma o la Degeneración Macular Asociada a la Edad. / Neurodegenerative diseases are characterized by degeneration and death of neurons which are unable to recover after a given insult, thus impairing functional recuperation. Because of this, there is no cure for diseases such as Alzheimer, Parkinson or Glaucoma. The retina is a projection of the central nervous system (CNS) located in the eye and therefore, isolated from the rest of the CNS. This makes the retina a very good model for experimental manipulation. In this work we have studied the functional changes in the retina by full field electroretinograme (ERG). This technique records the electric response of the retina after presentation of homogeneous light stimuli. We have studied the effects that optic nerve sections, increase of the intraocular pressure and phototoxicity have on ERG recordings. These lesions impair selectively certain retinal neuronal populations and imitate neurodegenerative diseases as Glaucoma or Age-related Macular Degeneration.

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