22 August 2012
M.Phil. / The record cards of all patients (21 554) examined by the eye clinic on the Phelophepa Mobile Health Care train during January and September, 1995 were analysed. The prevalence of. POAG in the sample was 0-.8% (177 of 21 554 persons). Differences in POAG prevalence were observed with respect to sex, age and geographical region. There was a significant difference (p<0.001) in the number of males (1.1%, 92 of 8113), compared to females (0.6%, 85 of 13 441) diagnosed with POAG. In persons over 40 years of age the prevalence rate was 1.2 % (166 of 14 254 persons) and in persons over 60 years the rate was 1.7% (110 of 6375 persons). The highest prevalence rate was found in the Western Cape (1.84%) and the lowest in the Eastern Cape (0.33%). POAG patients were compared to a control group to investigate the role of certain demographic, systemic and ocular factors. Risk factor analysis identified old age(> 60 years) (OR = 7.2, 95% CI = 4.4 - 11.7), geographical area (Western Cape, OR =2.5, 95% CI = 1.7 - 3.9), systolic hypertension (OR = 2.2, 95% CI = 1.3 - 3.7), diastolic perfusion pressure (< 40 mmHg, OR = 12.9, 95% CI = 4.2 - 52.9), myopia (OR = 2.7, 95% CI = 1.7 - 4.4) and elevated IOP (21 - 30 mmHg, OR = 12.6, 95% CI = 6.4 - 25.0) as significant risk factors. The effectiveness of employing certain blood pressure (BP) and intraocular pressure (TOP) variables as screening tools for glaucoma was evaluated. The systolic BP/IOP ratio was the most valid of the four tests evaluated (sensitivity = 66.0%, specificity = 98.2%, phi coefficient = 0.72). The study recommends that glaucoma screening programmes need to be developed which include sphygmomanometry as part of a battery of tests, and these programmes be targeted specifically at high risk populations (elderly, hypertensives). Further epidemiological studies are required which investigate reasons for the geographical differences found with respect to glaucoma prevalence.
Detection of retinal nerve fiber layer progression in glaucoma. / CUHK electronic theses & dissertations collectionJanuary 2013 (has links)
Yu, Chak Yan Marco. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 153-178). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong,  System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
A comparison of intraocular pressure measurements using rebound tonometry (iCare® tonometer) and applanation tonometry (Goldmann tonometer) in a South African clinical setting15 July 2015 (has links)
M.Phil. (Optometry) / The primary aim of this research was to investigate whether the Icare® rebound tonometer may be used in place of the Goldmann tonometer to obtain accurate and reliable intraocular pressure measurements on a sample of the general population seeking eye care, in a South African context. Due to the portability of the Icare®, lack of dependency on other instrumentation and power source, together with the ease of use with minimal training, and without the use of topical anaesthetic favourable results of the instrument may lead to its widespread use. This could aid in earlier diagnosis of glaucoma where intraocular pressure remains the only modifiable risk factor. In the South African context, where a high prevalence of undiagnosed primary open angle glaucoma has been found, access and accuracy of intraocular pressure measurement could save and extend functional vision in this country. Patients presenting at the Department of Optometry for routine eye examinations were selected utilizing convenience sampling. The right and left eyes of 113 patients were assessed using both the Icare® TA01i and the Goldman applanation tonometer by independent examiners for each method, all readings of intraocular pressure with the Goldman being taken by the same experienced examiner. The age of the patients ranged from 20 to 89 years with a mean age 50.29 ±20.97 years. Using the Oculus Pachycam® when it became available, central corneal thickness was obtained on 71 patients (142 eyes). Analysis of data using descriptive statistics from SPSS (Statistical Programs for the Social Sciences) was performed in addition to the Bland-Altman method of comparative analysis for sets of data of corrected and uncorrected measurements between the instruments...
Landers, John Arthur W. G.
Background : Frequency Doubling Perimetry ( FDP ) is a recently developed form of perimetry, which may be more sensitive for detecting visual field loss from glaucoma than conventional Achromatic Automated Perimetry ( AAP ). This thesis was undertaken to study aspects of FDP for the detection of early glaucoma. Method : FDP was compared with other forms of perimetry at one point in time using one dataset ( n = 83 ) and longitudinally over a four - year period with another dataset ( n = 62 ). Several aspects were studied : ( 1 ) the ability of FDP to detect visual field loss earlier than AAP, ( 2 ) its ability to detect early functional abnormality in the presence of mild glaucomatous structural abnormality ( 3 ) visual field topography compared with other perimetry and ( 4 ) its ability to predict future field loss when only the nasal quadrants were considered. Results : When subjects at risk of glaucoma with initial visual field loss on FDP were followed over a three - year period, a significant proportion developed field loss with AAP, whilst those without initial FDP loss did not. FDP detected cases of early glaucomatous optic disc damage, which had not been detected using AAP ; however, there was still a proportion of those with abnormal optic discs which remained normal on FDP. FDP field topography was hill - shaped with the most sensitive point centrally ; however, it was considerably flatter and more sensitive than AAP. Finally, if FDP field loss was only considered significant when it occurred within the nasal step location of the visual field, then this may improve the accuracy of glaucoma diagnosis. Conclusion : This thesis has demonstrated that FDP is not only more sensitive than AAP in the detection of glaucomatous optic disc damage, but it is able to predict future field loss on AAP. FDP may therefore be useful in the early detection and management of glaucoma. / Thesis (Ph.D.)--School of Medicine, 2006.
Angiulo, Cindy Lou
No description available.
Evaluation of retinal nerve fiber layer measurement with spectral-domain optical coherence tomography in glaucoma. / CUHK electronic theses & dissertations collectionJanuary 2012 (has links)
青光眼作為一種慢性進展性視神經病變，已經成為世界眼科病變中導致不可逆盲的首要原因。青光眼的早期診斷和治療對於降低疾病進展的風險至關重要。光學相干斷層掃描（OCT）可以提供在體視網膜橫斷面的視圖，從而實現了對視網膜神經纖維層（RNFL）改變的客觀測量，這些改變已經被證明了與青光眼引起的視神經損害相關，並已成為診斷青光眼的重要參考依據。 / 頻域OCT是最新一代的光學相干斷層掃描，它具有比時域OCT更快的掃描速度和更高的圖像解析度，因此，頻域OCT可以提供更可靠的RNFL厚度測量和RNFL缺損評估。本文的研究目的在於評估頻域OCT對RNFL厚度的重測再現性，以及探討影響RNFL厚度測量的因素，這些因素包括（1）影像平均法的應用，（2）RNFL分層錯誤，和（3）視網膜血管的影響。此外，由於RNFL攝影是一個評估青光眼RNFL缺損的臨床參考標準，我們還將其對RNFL缺損的測量與頻域OCT的RNFL厚度偏差圖所作出的測量進行了比較。 / 首先，為了評估頻域OCT對RNFL厚度測量的重測再現性，15名正常人和15名青光眼患者連續四周每週均接受一次OCT掃描。正常組和青光眼組的RNFL厚度再現性係數分別為4.77-12.65微米和4.53-16.66微米，由於組內相關性係數均大於0.773，說明頻域OCT所作出的RNFL厚度測量是具備可重複性的。 / 其次，通過分析54隻眼（25名正常志願者和29名青光眼患者）的RNFL厚度測量值，本文對圖像平均法的應用是否會影響RNFL厚度的測量這一問題進行了探討。分析中，每一隻眼均接受了3次OCT掃描，3次掃描的圖像分別使用2、8、和16張連續的圖像進行影像平均。結果顯示，除了青光眼組的鼻下象限RNFL厚度測量值之外（P=0.036），不同的圖像幀數並不會對兩組的總體和其它各象限的RNFL厚度測量值產生顯著的影響（P≥0.055）。雖然圖像平均法的應用對RNFL厚度測量的影響並不顯著，但是視網膜血管和RNFL分層錯誤對青光眼,尤其是對RNFL非常薄的晚期青光眼患者的RNFL厚度測量有影響。結論來自對60個正常人，66個輕至中度青光眼（MD≥-6 dB）患者和54個嚴重青光眼（MD<-6 dB）患者的共180張OCT圖像的分析。視網膜血管相對於平均RNFL厚度的比例均值在正常組，輕至中度青光眼組，和嚴重青光眼組分別為11.2±2.3，12.6±2.5，和16.6±3.9。在人為調整了RNFL界限以糾正RNFL分層錯誤的前後，總體RNFL厚度的差異範圍在正常組為-3.0-2.5微米，輕至中度青光眼組為-2.5-5.0微米，嚴重青光眼組為-11.0-9.5微米組。 / 最後，通過對41名青光眼患者的51隻眼的RNFL缺損面積，位置，和覆蓋角度進行測量，本文將頻域OCT作出的測量結果和共焦鐳射掃描檢眼鏡（CSLO）RNFL反射影像圖的測量結果進行了比較，結果顯示：OCT不但可以檢測到所有出現在CSLO的RNFL反射影像圖上的RNFL缺損，更重要的是，OCT還可以檢測出額外的並未在RNFL反射影像圖上出現的RNFL缺損。 / 總之，頻域OCT是一種可提供高再現性RNFL厚度測量的影像方法。對青光眼,尤其是晚期青光眼的RNFL厚度測量值的詮釋，應當考慮到視網膜血管和RNFL分層錯誤的影響。OCT具備對RNFL缺損進行多維度量化（包括厚度，面積，位置，和覆蓋角度）的能力，在青光眼RNFL改變的檢測和監測方面，相對于傳統的RNFL攝影，OCT無疑是更有效的選擇。 / Glaucoma, a chronic progressive optic neuropathy, is the leading cause of irreversible blindness in the world. An early diagnosis and treatment of glaucoma is vital to reduce the risk of disease progression. Providing a cross-sectional view of the retina in vivo, optical coherence tomography (OCT) can objectively measure the changes of retinal nerve fiber layer (RNFL), which has been shown to be of relevance and importance in detecting glaucomatous damage of the optic nerve. / The latest generation of OCT, the spectral-domain OCT, has a faster scan speed and a higher image resolution compared to the time-domain OCT. It is expected that the spectral-domain OCT would allow a more reliable measurement of the RNFL thickness and assessment of RNFL defects. The objectives of this research project were to examine the test-retest reproducibility of spectral-domain OCT RNFL measurement and investigate factors including (1) image averaging, (2) segmentation failure, and (3) contribution of retinal blood vessels that might affect the measurement of RNFL thickness. As RNFL photography is a reference standard to evaluate RNFL defects in glaucoma, we also evaluated whether RNFL defects measured in the spectral-domain OCT RNFL thickness map would be comparable to those detected in RNFL photographs. / To evaluate the test-retest reproducibility of RNFL measurements obtained by the spectral-domain OCT, 15 normal individuals and 15 glaucoma patients were followed and imaged weekly for 4 consecutively weeks. The reproducibility coefficients of RNFL thicknesses ranged between 4.53 and 16.66 μm for the normal group, and 4.77 and 12.65 μm for the glaucoma group. The intraclass correlation coefficients were all above 0.773, indicating RNFL measurement with spectral-domain OCT was reproducible. / We then investigated if multiple-image averaging would influence the measurement of RNFL thickness. A total of 54 eyes from 25 normal volunteers and 29 glaucoma patients with RNFL images captured and averaged with 2, 8, and 16 consecutive image frames were analyzed. For both groups, there were no significant differences in global or sectoral RNFL thicknesses among the image series averaged with different number of image frames (all with P≥0.055) except for the inferonasal sector in the glaucoma group (P=0.036). Although the impact of image averaging on RNFL measurement was insignificant, the presence of retinal blood vessels and segmentation errors were influential on the measurement, particularly in advanced glaucoma patients when the RNFL was thin. Analyzing a total of 180 eyes from 60 normal individuals, 66 mild to moderate (MD≥-6 dB) and 54 advanced (MD<-6 dB) glaucoma patients, the mean proportion of retinal blood vessels relative to the average RNFL thickness was 11.2±2.3%, 12.6±2.5% and 16.6±3.9%, respectively. After correcting the segmentation errors by manually refining the RNFL boundaries, the differences in average RNFL thickness ranged from -3.0 to 2.5 m in the normal, -2.5 to 5.0 m in the mild to moderate glaucoma and -11.0 to 9.5 m in the advanced glaucoma groups. / Finally, we compared the area, the angular location, and the angular width of RNFL defects from 51 eyes of 41 glaucoma patients measured with the spectral-domain OCT and RNFL reflectance images obtained by a confocal scanning laser ophthalmoscope (CSLO). OCT was able to detect areas of RNFL abnormalities in all eyes with RNFL defects which were evident in the CSLO RNFL reflectance images. More important, OCT could identify additional RNFL thinning not apparent in RNFL reflectance images. / In summary, spectral-domain OCT could offer an effective approach in measuring RNFL with high reproducibility. Interpretation of RNFL measurement should take the contribution of the retinal blood vessels and segmentation errors into consideration, particularly in advanced glaucoma when the RNFL is thin. With the ability to quantify multiple dimensions of RNFL defects (thickness, area, angular location, and angular width), OCT could provide a useful alternative to detect and monitor RNFL changes in glaucoma. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Ye, Cong. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 117-130). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong,  System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / ABSTRACT --- p.i / 摘要 (ABSTRACT IN CHINESE) --- p.v / DEDICATION --- p.viii / ACKNOWLEDGEMENT --- p.ix / TABLE OF CONTENTS --- p.x / PUBLICATIONS --- p.xiv / ABBREVIATIONS --- p.xvi / Chapter CHAPTER 1: --- INTRODUCTION --- p.1 / Chapter 1.1 --- Glaucoma --- p.2 / Definition of Glaucoma --- p.2 / Epidemiology of Glaucoma --- p.3 / Pathogenesis of Glaucoma --- p.4 / Diagnosis of Glaucoma --- p.7 / Chapter 1.2 --- Retinal Nerve Fiber Layer --- p.13 / Anatomy of Retinal Nerve Fiber Layer --- p.13 / Visualization of Retinal Nerve Fiber Layer --- p.14 / Retinal Nerve Fiber Layer Defect in Glaucoma --- p.16 / Significance of Detecting Retinal Nerve Fiber Layer Defect in Glaucoma --- p.18 / Chapter 1.3 --- Optical Coherence Tomography --- p.20 / Principle of Optical Coherence Tomography --- p.20 / Retinal Nerve Fiber Layer Imaging with OCT --- p.21 / Optic Nerve Head Imaging with OCT --- p.27 / Advantages and Disadvantages of Optical Coherence Tomography --- p.29 / Chapter 1.4 --- Research Objectives --- p.30 / Chapter CHAPTER 2: --- GENERAL MATERIALS AND METHODS --- p.32 / Chapter 2.1 --- Subject Enrollments --- p.33 / Chapter 2.2 --- Clinical Ophthalmic Examination --- p.34 / Chapter 2.3 --- Visual Field Examination --- p.35 / Definition of Normal and Glaucoma Groups --- p.35 / Chapter 2.4 --- Optical Coherence Tomography Imaging --- p.37 / Cirrus HD-OCT Imaging --- p.37 / Spectralis OCT Imaging --- p.37 / Chapter 2.5 --- Statistical Analysis --- p.39 / Chapter CHAPTER 3: --- RETINAL NERVE FIBER LAYER IMAGING WITH SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY --- p.40 / Chapter 3.1 --- Reproducibility and Agreement of Retinal Nerve Fiber Layer Measurement --- p.41 / Introduction and Study Objectives --- p.41 / Methods --- p.42 / Results --- p.45 / Discussion --- p.47 / Tables and Figures --- p.51 / Chapter 3.2 --- Effect of Multiple B-scans Averaging on Retinal Nerve Fiber Layer Measurement --- p.58 / Introduction and Study Objectives --- p.58 / Methods --- p.59 / Results --- p.61 / Discussion --- p.62 / Tables and Figures --- p.67 / Chapter 3.3 --- Impact of Blood Vessels and Segmentation Failure on Retinal Nerve Fiber Layer Measurement --- p.73 / Introduction and Study Objectives --- p.73 / Methods --- p.75 / Results --- p.78 / Discussion --- p.80 / Tables and Figures --- p.84 / Chapter 3.4 --- Agreement of Localized Retinal Nerve Fiber Layer Defect Assessment with Confocal Scanning Laser Ophthalmoscopy --- p.95 / Introduction and Study Objectives --- p.95 / Methods --- p.97 / Results --- p.101 / Discussion --- p.103 / Tables and Figures --- p.108 / Chapter CHAPTER 4: --- GENERAL CONCLUSIONS --- p.115 / REFERENCES --- p.117
The characterization of retinal nerve fiber layer thickness in normal,high-tension and normal-tension glaucoma using optical coherencetomographyMok, Kwok-hei., 莫國熙. January 2005 (has links)
published_or_final_version / abstract / Anatomy / Doctoral / Doctor of Philosophy
Applications of optical coherence tomography imaging in the assessment of glaucoma. / CUHK electronic theses & dissertations collectionJanuary 2006 (has links)
Although the current OCT imaging system was designed to examine the retinal structures, a novel application in imaging the anterior chamber angle was studied in section 3.7. OCT was demonstrated to be clinically useful for visualization of the different patterns of angle configurations in different forms of angle closure glaucoma. / In section 3.5, RNFL measurement by OCT was cross-validated by another nerve fiber analyzer, scanning laser polarimetry (SLP). While both OCT and SLP demonstrated comparable diagnostic performance for glaucoma detection and high correlation in the respective RNFL measurements, OCT was found to provide a closer estimation of RNFL thickness with reference to the reported histological measurements. In section 3.6, the structural-functional relationship between RNFL thickness and visual sensitivity was evaluated and compared between OCT and SLP. The relationships were found to be dependent on the choice of the perimetry scale, the type of RNFL measuring devices and the characteristics of the studied subjects. It was concluded that regression analysis of the structural-functional profile could provide important information in the assessment of the trend and pattern of glaucoma progression. / In summary, optical coherence tomography was shown to be useful in the diagnosis of glaucoma and in the evaluation of the trend and pattern of disease progression. / Objectives. The research project was designed to investigate the applications of optical coherence tomography in the assessment of glaucoma. The goals are to identify sensitive and specific anatomic markers, and analytical method for detection of glaucomatous changes, to evaluate the intricate structural-functional relationships in glaucoma with regression analysis and to assess the potential application of optical coherence tomography imaging system in visualization of the anterior chamber angle with a view to obtain OCT data to help understanding the pathophysiology of different forms of angle-closure glaucoma. / Sections 3.1 to 3.3 were designed to identify the most sensitive and specific diagnostic marker(s) for glaucoma detection. Peripapillary retinal nerve fiber layer (RNFL), macular thickness, optic nerve head parameters measured with different reference planes, and a novel anatomic marker - macular nerve fiber layer were investigated. The averaged peripapillary RNFL thickness measured with a high resolution scan (512 scan point) was found to have the best discriminating power for detection of glaucoma. It also has the strongest correlation with visual function. To examine if utilization of the complete data profile of peripapillary RNFL could further improve diagnostic sensitivity, a novel approach with the use of neural network trained to recognize RNFL pattern was studied in section 3.4. It was concluded that neural network analysis could enhance the diagnostic performance for glaucoma detection. / Summary. Glaucoma is a progressive optic neuropathy characterized by the loss of retinal ganglion cells resulting in constriction of visual field and loss of vision as the disease progresses. Since structural damage in glaucoma occurs well before any detectable loss in visual function, clinical examination of the optic nerve head and its nerve fiber layer is crucial in establishing the diagnosis, monitoring the progression and initiating treatment before irreversible damage takes place. The present research project is composed of 7 coherent studies (sections 3.1 to 3.7), aiming to investigate the clinical applications of optical coherence tomography (OCT), an advanced imaging device for detailed examination of optic nerve head and nerve fiber layer, in the assessment of glaucoma. / Leung Kai-shun. / "June 2006." / Adviser: Chi Pui Pang. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6323. / Thesis (M.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 212-227). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong,  System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / School code: 1307.
Modeling the Structure-Function Relationship between Retinal Ganglion Cells and Visual Field Sensitivity and the Changes Due to Glaucomatous NeuropathyRaza, Ali Syed January 2014 (has links)
Relatively new technology called optical coherence tomography allows direct and non invasive in vivo imaging of retinal anatomy in human subjects. There are several interesting applications of this technique, including testing models relating retinal anatomy (structural measures) to behavioral thresholds of light sensitivity (functional measures). In addition to potentially improving our understanding of this relationship and how it changes during the course of neurodegenerative diseases of the eye such as glaucoma, analyses of these data may allow for early identification of glaucomatous neural damage in the retina, which has considerable clinical relevance. Here, the underlying assumptions and generalization of a previously developed model of the structure function relationship in glaucoma was tested by applying this model to a novel dataset. This model has been influential in the literature because it purports to accurately estimate the number of retinal ganglion cells; however, it was found to have several questionable assumptions and did not generalize well. Next, a new method of estimating the number of retinal ganglion cells from optical coherence tomography was developed. This method uses fewer and more defensible assumptions and demonstrated good agreement with independent histological estimates. Finally, a new method, using computer simulations, was developed for analyzing data from optical coherence tomography in order to distinguish early signs of glaucomatous changes in retinal anatomy from variability in structure among healthy retinas, and this method performed better than previously published techniques.
Application of polarization sensitive optical coherence tomography (PS-OCT) and phase sensitive optical coherence tomography (PhS-OCT) for retinal diagnosticsParanjape, Amit Shrikant 22 June 2011 (has links)
An Enhanced Polarization-Sensitive Swept Source Optical Coherence Tomography (EPS-SS-OCT) instrument for high sensitivity cross-sectional imaging of Retinal Nerve Fiber Layer (RNFL) has been designed, constructed, and verified. The instrument is capable of measuring the thickness and birefringence of the RNFL. Birefringence change of the RNFL could serve as an early indicator of glaucoma. The associated image processing methods for completely automated, time efficient algorithm to segment the RNFL in images of the human retina recorded by the EPS-SS-OCT. Detected RNFL boundaries are used to compute peripapillary thickness maps. Numerical algorithms to compute the birefringence of the detected RNFL layer are presented along with the associated phase retardation and birefringence peripapillary maps. Glaucoma affects the vitality of retinal ganglion cell axons in the retinal nerve fiber layer (RNFL) and may be clinically detected through a change in RNFL birefringence. Comprehensive peripapillary maps of healthy and glaucoma suspect human RNFL birefringence were constructed using EPS-SS-OCT. Presence of macrophages is a hallmark of several retinal diseases such as drusen and age related macular degeneration. Application of photothermal Optical Coherence Tomography (OCT) to detect macrophages in ex vivo arteries which have engulfed nanoclusters of gold coated iron oxide (nanorose) is reported. Nanorose engulfed by macrophages in arteries absorb incident laser (800nm) energy and cause optical pathlength (OP) variation which is measured using photothermal OCT. OP variation in polydimethyl siloxane tissue phantoms containing varying concentrations of nanorose match values predicted from nanoparticle and material properties. Measurement of OP variation in arteries in response to laser excitation provides an estimate of nanorose concentration in arteries 2.5x109 particles/ml. OP variation in nanoparticle containing artery sections and tissue phantoms taking up nanorose has a different magnitude and profile from that observed in control aorta and phantoms without macrophages and is consistent with macrophage presence as identified with RAM-11 histology staining. Our results suggest that tissue regions with macrophages taking up nanorose can be detected using photothermal OCT. / text
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