Review on Region-Based Segmentation Using Watershed and Region Growing Techniques and their Applications in Different Fields

In digital image processing and computer vision, segmentation operation for an image refers to dividing an image into multiple image segments, and the significant purpose of segmentation operation is to depict an image in a way so that the analysis process of the objects of interest is easier and more accurate. The region-based segmentation scheme act for finding similarities between adjacent pixels to detect each region that constructs the image. Similarity scales have based on different features, in a grayscale image, the scale may be referred to as textures and other spatial appearances, and also the variance in intensity of a region and so on. Significantly, many applications in different fields involved region-based segmentation for instance remote sensing, medical application, and others for recognizing interesting objects in an image. In this paper, two techniques for segmentation operation in region-based which are region growing and watershed are reviewed

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

The Retinal Microvasculature in Secondary Progressive Multiple Sclerosis

In light of new data regarding pathology of multiple sclerosis (MS), more research is needed into the vascular aspects of the disease. Demyelination caused by inflammation is historically thought of as the main cause of disability in the disease. Recent studies, however, have suggested that MS is in fact a spectrum of overlapping phenotypes consisting of inflammation, oxidative damage and hypoperfusion. The microvasculature plays an important role in all of these pathogenic processes and its dysfunction may therefore be of crucial importance to the development and progression of the disease. This thesis focuses on investigating the microvasculature of the retina as a surrogate for the brain by assessing the vascular structure, blood flow dynamics and oxygen transfer of the retinal blood vessels in secondary progressive multiple sclerosis (SPMS). Studying the retinal microvasculature using a multimodal imaging approach has allowed us to develop a more detailed understanding of blood flow in MS and to identify new imaging markers for trials into neuroprotective drugs in MS. The work done in this thesis demonstrated; i) a higher rate of retinal microvascular abnormalities in MS which progresses with disease severity, ii) evidence of retinal vascular remodelling in SPMS and iii) changes in blood velocity and flow in the retina in SPMS. These observations pave the way for future investigations into the mechanisms of vascular alterations and vascular dysfunction in MS, and provide a set of imaging markers to further explore other cerebrovascular diseases through the retina

The development of a clinical trial protocol and functional biomarkers for age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness amongst older adults in the developed world. With the predicted rise in the ageing population over the next decades, the prevalence of this debilitating disease will simply continue to increase. The only treatments currently available are for advanced neovascular AMD. The retina is already severely compromised by this stage in disease development. Therefore, there is a pressing need to evaluate potential novel interventions that aim to prevent the development of advanced disease in people with early AMD, to prevent sight loss from occurring. Furthermore, it is necessary to develop tests that are sensitive to subtle changes in visual function in order to evaluate the efficacy of these emerging treatments. There is a growing body of evidence to suggest that hypoxia contributes to the development of AMD. Hypoxia is most acute at night when the retinal photoreceptors are most metabolically active, due to the demands of the rod dark current. Increasing the light levels at night will cause the oxygen demand, and hence the hypoxia, to be substantially diminished. This leads to the hypothesis that providing low level night time light therapy to people with early AMD may slow disease progression by reducing hypoxia. In order to evaluate the potential effectiveness of such an intervention, it is necessary to select appropriate outcome measures. The inherent variability of the standard test of visual function, visual acuity, renders it inappropriate for use as a primary outcome measure in proof of concept clinical trials. Therefore, the first aim of this thesis was to evaluate the diagnostic validity and repeatability of alternative functional tests that may be used as biomarkers for early macular disease. Dark adaptation was evaluated using three stimuli, a spot of 2o radius and annuli of 7o and 12o radii, in 21 healthy adults (on two occasions) and in 11 participants with early AMD. All stimuli were found to be highly diagnostic for early AMD. The spot of 2o radius provided the best separation between groups with respect to the time constant of cone recovery (area under the ROC curve 0.91). The repeatability of chromatic and flicker thresholds were also assessed in 30 healthy adults. The coefficient of repeatability, expressed as a percentage of the mean threshold, was 17.1% for red-green chromatic thresholds, 31.1% for blue-yellow, 53.4% for 14Hz flicker thresholds, and ranged between 36.4%-53.3% for parameters of dark adaptation. A small learning effect was found for both chromatic thresholds and the 14-Hz flicker test, indicating that a control group is needed in studies of new therapeutic interventions. The second aim of this thesis was to develop a protocol for a clinical trial that seeks to determine if low level night time light therapy can prevent the progression of early AMD. The level of retinal illuminance required to suppress the rod dark current, the maximum retinal illuminance which prevents substantial suppression of melatonin secretion, and the most appropriate means of delivering the dose of retinal illumination were evaluated. The final protocol employed an organic LED illuminated light mask, worn during hours of sleep, as the mode of intervention. In conclusion, this thesis has confirmed that cone dark adaptation is a sensitive functional biomarker for AMD, and that all three functional tests have a good inter-session repeatability. These biomarkers will be validated in the prospective clinical trial of low-level light therapy to confirm their prognostic and predictive capabilities. The proposed trial will also evaluate the effectiveness of the low level night time light therapy, delivered by means of an illuminated light mask, at slowing the progression of early AMD

Low-level night-time light therapy for age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of visual impairment in the developed world (Wong et al., 2014). The exact causes of AMD are unclear but hypoxia has been implicated (Stefánsson et al., 2011). If hypoxia has a role in the pathogenesis of AMD treatments that mitigate the effect of retinal hypoxia may slow disease progression. This thesis aimed to establish the impact of light therapy, as delivered using a light emitting mask, on the progression of AMD. A phase I/IIa randomised controlled trial was implemented in which 60 participants with early and intermediate AMD were allocated to the intervention or the untreated control group in a 1:1 ratio and monitored over 12 months. The ability of secondary outcome measures (including: rate of cone dark adaptation, 14Hz flicker threshold and chromatic thresholds) to identify the likely risk of progression from early and intermediate AMD to advanced AMD was also assessed in a cross-sectional study evaluating the relationship between each baseline outcome measure and the severity of fundus changes. Sixty participants were recruited of which 47 (20 intervention, 27 control) completed the 12 month follow-up period. No significant difference was found in the change of any parameter between groups apart from the time constant of cone-photoreceptor recovery (cone τ), which was increased to a greater extent in the treated group. An additional 40 participants were recruited to the cross-sectional study (n=100). Measurement of cone τ was identified as the best independent predictor of increased AMD severity based on the AREDS Simplified Severity Scale (Ferris et al., 2005). Although a greater proportion of controls (48%) than mask wearers (38%) showed disease progression over the duration of the trial this difference did not reach statistical significance

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