Retinal structure and function in age-related maculopathy

Age-related macular degeneration (AMD) is the principle cause of visual loss and blindness in the developed world. As new treatments and therapies are developed the need to better diagnose and then monitor outcomes of treatment has become more important. This thesis evaluates both structural and functional changes that occur in the early stage of AMD, known as age-related maculopathy (ARM), with the aim of determining their diagnostic potential. This thesis also explores the relationship between structural and functional parameters. Twenty four participants with ARM and 26 control participants were recruited. Retinal function was probed using four focal electroretinography (ERG) techniques: the focal cone ERG, focal flicker ERG, ERG photostress test and focal rod ERG. Long wavelength optical coherence tomography (OCT) was used to assess retinal structure, specifically retinal, choroidal and four intra-retinal layer thicknesses at 21 macular locations. These techniques were initially developed and optimised for the detection of AMD related changes. The ability of each parameter to diagnose ARM was assessed. Correlation and linear regression analyses were carried out to identify any relationships between retinal structure and function in healthy controls. Retinal thickness was reduced in participants with ARM at parafoveal locations (~2° eccentricity), but choroid thickness was unaffected. Diagnostically, focal ERG parameters provided better sensitivity and specificity to ARM than OCT measures, with the ERG photostress test providing the best diagnostic potential. No strong relationships were shown between any ERG parameter and any retinal or choroidal layer volume in control participants. Three ERG parameters were shown to be related to specific retinal features of ARM, but the strongest associations were between ERG photostress test recovery and focal cone ERG b-wave implicit time and a diagnosis of wet AMD in the contralateral eye. In conclusion the structural and functional parameters assessed appeared to provide independent information regarding disease status and severity. ERG parameters showed better diagnostic potential than OCT measures. The single most diagnostic parameter was the recovery time constant of the ERG photostress test

Retinal structure and function in age-related maculopathy

Age-related macular degeneration (AMD) is the principle cause of visual loss and blindness in the developed world. As new treatments and therapies are developed the need to better diagnose and then monitor outcomes of treatment has become more important. This thesis evaluates both structural and functional changes that occur in the early stage of AMD, known as age-related maculopathy (ARM), with the aim of determining their diagnostic potential. This thesis also explores the relationship between structural and functional parameters. Twenty four participants with ARM and 26 control participants were recruited. Retinal function was probed using four focal electroretinography (ERG) techniques: the focal cone ERG, focal flicker ERG, ERG photostress test and focal rod ERG. Long wavelength optical coherence tomography (OCT) was used to assess retinal structure, specifically retinal, choroidal and four intra-retinal layer thicknesses at 21 macular locations. These techniques were initially developed and optimised for the detection of AMD related changes. The ability of each parameter to diagnose ARM was assessed. Correlation and linear regression analyses were carried out to identify any relationships between retinal structure and function in healthy controls. Retinal thickness was reduced in participants with ARM at parafoveal locations (~2° eccentricity), but choroid thickness was unaffected. Diagnostically, focal ERG parameters provided better sensitivity and specificity to ARM than OCT measures, with the ERG photostress test providing the best diagnostic potential. No strong relationships were shown between any ERG parameter and any retinal or choroidal layer volume in control participants. Three ERG parameters were shown to be related to specific retinal features of ARM, but the strongest associations were between ERG photostress test recovery and focal cone ERG b-wave implicit time and a diagnosis of wet AMD in the contralateral eye. In conclusion the structural and functional parameters assessed appeared to provide independent information regarding disease status and severity. ERG parameters showed better diagnostic potential than OCT measures. The single most diagnostic parameter was the recovery time constant of the ERG photostress test.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

An automated image processing system for the detection of photoreceptor cells in adaptive optics retinal images

The rapid progress in Adaptive Optics (AO) imaging, in the last decades, has had a transformative impact on the entire approach underpinning the investigations of retinal tissues. Capable of imaging the retina in vivo at the cellular level, AO systems have revealed new insights into retinal structures, function, and the origins of various retinal pathologies. This has expanded the field of clinical research and opened a wide range of applications for AO imaging. The advances in image processing techniques contribute to a better observation of retinal microstructures and therefore more accurate detection of pathological conditions. The development of automated tools for processing images obtained with AO allows for objective examination of a larger number of images with time and cost savings and thus facilitates the use of AO imaging as a practical and efficient tool, by making it widely accessible to the clinical ophthalmic community. In this work, an image processing framework is developed that allows for enhancement of AO high-resolution retinal images and accurate detection of photoreceptor cells. The proposed framework consists of several stages: image quality assessment, illumination compensation, noise suppression, image registration, image restoration, enhancement and detection of photoreceptor cells. The visibility of retinal features is improved by tackling specific components of the AO imaging system, affecting the quality of acquired retinal data. Therefore, we attempt to fully recover AO retinal images, free from any induced degradation effects. A comparative study of different methods and evaluation of their efficiency on retinal datasets is performed by assessing image quality. In order to verify the achieved results, the cone packing density distribution was calculated and correlated with statistical histological data. From the performed experiments, it can be concluded that the proposed image processing framework can effectively improve photoreceptor cell image quality and thus can serve as a platform for further investigation of retinal tissues. Quantitative analysis of the retinal images obtained with the proposed image processing framework can be used for comparison with data related to pathological retinas, as well as for understanding the effect of age and retinal pathology on cone packing density and other microstructures

Advances in Ophthalmology

This book focuses on the different aspects of ophthalmology - the medical science of diagnosis and treatment of eye disorders. Ophthalmology is divided into various clinical subspecialties, such as cornea, cataract, glaucoma, uveitis, retina, neuro-ophthalmology, pediatric ophthalmology, oncology, pathology, and oculoplastics. This book incorporates new developments as well as future perspectives in ophthalmology and is a balanced product between covering a wide range of diseases and expedited publication. It is intended to be the appetizer for other books to follow. Ophthalmologists, researchers, specialists, trainees, and general practitioners with an interest in ophthalmology will find this book interesting and useful

Glaucoma

This book addresses the basic and clinical science of glaucomas, a group of diseases that affect the optic nerve and visual fields and is usually accompanied by increased intraocular pressure. The book incorporates the latest development as well as future perspectives in glaucoma, since it has expedited publication. It is aimed for specialists in glaucoma, researchers, general ophthalmologists and trainees to increase knowledge and encourage further progress in understanding and managing these complicated diseases

Aspects of structural and functional assessment in open angle glaucoma

Early detection of glaucoma is a prerequisite for effective management of the disease. The study was concerned with aspects of structural and functional assessment in open angle glaucoma. The major part of the study was concerned with the utilization of digital stereoscopic imaging of the optic nerve head in the detection of open angle glaucoma (OAG). Specifically, it addressed possible sources of variability that confound the diagnosis of glaucoma and are associated with the monoscopic, as opposed to stereoscopic, observation of the optic nerve head (ONH) the limited diagnostic value of the features of the peripapillary retina accompanying glaucomatous damage and the between-observer variation in the subjective evaluation of the ONH. The study utilised a dataset of magnification corrected digital images from 51 normal individuals and from 113 patients with OAG. Misdiagnosis of glaucoma was associated with discrepancies in the evaluation of the rim area due to the monoscopic presentation of the ONH masking the presence of focal rim loss, otherwise evident with stereoscopic observation. The frequency and patterns of distribution of the alpha and beta peripapillary atrophy (PPA) were confirmed among normal and glaucomatous eyes but meaningful conclusions on the diagnostic value of PPA were hindered by the clinically broad criteria of this feature. Regression analysis of the global and sectorial rim areas for the discrimination of glaucomatous damage compared favourably with the subjective glaucoma diagnosis by expert observers. The remaining part of the study was concerned with the evaluation of the Total and Pattern Deviation probability analysis in short-wavelength perimetry (SWAP). The material comprised the Humphrey Field Analyzer single field print-outs from standard automated perimetry (SAP) and from SWAP of 53 normal individuals 18 patients with cataract, 22 with OHT and 55 with OAG. Focal visual field loss derived by SWAP was markedly less compared to SWAP indicating wider limits of normality for SWAP. Considerable caution should be exercised before the use of SWAP

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 385)

This bibliography lists 536 reports, articles and other documents introduced into the NASA Scientific and Technical Information System Database. Subject coverage includes: aerospace medicine and physiology, life support systems and man/system technology, protective clothing, exobiology and extraterrestrial life, planetary biology, and flight crew behavior and performance

Analytical validation of innovative magneto-inertial outcomes: a controlled environment study.

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