Automatic determination of vertical cup-to-disc ratio in retinal fundus images for glaucoma screening

Glaucoma is a chronic progressive optic neuropathy that causes visual impairment or blindness, if left untreated. It is crucial to diagnose it at an early stage in order to enable treatment. Fundus photography is a viable option for population-based screening. A fundus photograph enables the observation of the excavation of the optic disc - the hallmark of glaucoma. The excavation is quantified as vertical cup-todisc ratio (VCDR). The manual assessment of retinal fundus images is, however, time-consuming and costly. Thus, an automated system is necessary to assist human observers. We propose a computer aided diagnosis system, which consists of localization of the optic disc, determination of the height of the optic disc and the cup, and computation of the VCDR. We evaluated the performance of our approach on eight publicly available data sets, which have in total 1712 retinal fundus images.We compared the obtained VCDR values with those provided by an experienced ophthalmologist and achieved a weighted VCDR mean difference of 0:11. The system provides a reliable estimation of the height of the optic disc and the cup in terms of the Relative Height Error (RHE = 0:08 and 0:09, respectively). Bland-Altman analysis showed that the system achieves a good agreement with the manual annotations especially for large VCDRs, which indicate pathology

Vascular and morphological changes of the optic nerve head following therapeutic intraocular pressure reduction in open angle glaucoma and ocular hypertension

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

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

Retinal Haemodynamics in Primary Open Angle Glaucoma Patients with Differing Nocturnal Blood Pressure Profiles

The impairment of ocular haemodynamics has been reported in primary open angle glaucoma (POAG) patients using various blood flow measurement techniques. Studies have shown hypotension may accelerate progression in POAG and a marked nocturnal blood pressure reduction (NBPR) was reported to further expedite the neuro-degenerative disease. It has been suggested that extreme NBPR may be a form of systemic vascular dysregulation that is manifested as an ocular dysregulation, but this hypothesis has never been tested. In addition, the relationship, if any, of retinal haemodyanamics to magnitude of the NBPR is also unknown. A prototype Doppler spectral domain optical coherence tomographer (SD-OCT) together with the more established bi-directional Laser Doppler velocimetry with simultaneous vessel densitometry (BLDV-SVD) methodology (Canon Laser Blood Flowmeter, CLBF) were utilized to see if the NBPR is associated to impaired retinal haemodynamics in glaucoma patients. The specific aims of this thesis were: (1) To evaluate the association between retinal hemodynamics of healthy eyes with age, as derived by Doppler SD-OCT, (2) To evaluate retinal blood flow (RBF) in patients with early POAG and differing NBPR profiles, (3) To investigate the relationship between Doppler SD-OCT derived retinal haemodynamics and the retinal nerve fiber layer (RNFL) thickness in patients with early POAG and healthy age-matched controls, (4) To evaluate the vascular reactivity in patients with early POAG with different NBPR profiles using a normoxic hypercapnia provocation stimulus. Perfusion to the retina was not altered with increasing age among healthy people in the range of 20 to 70 years. Patients with early POAG who exhibited an exaggerated nocturnal reduction in mean arterial pressure also demonstrated lower RBF values as shown by the measurement of Doppler SD-OCT. The change in retinal circulation in early POAG was related to reduced RNFL thickness and a larger venous area may be associated with thicker RNFL among controls. Patients with early POAG who exhibited an exaggerated NBPR also demonstrated disturbance of retinal vascular reactivity

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

Special propedeutics of internal diseases

ВНУТРЕННИЕ БОЛЕЗНИКУРСЫ ЛЕКЦИЙПРОПЕДЕВТИКА ВНУТРЕННИХ БОЛЕЗНЕЙГИПЕРСЕНСИБИЛИЗАЦИЯЭНДОКРИННОЙ СИСТЕМЫ БОЛЕЗНИГЕМАТОЛОГИЧЕСКИЕ БОЛЕЗНИПОЧЕК БОЛЕЗНИУРОЛОГИЧЕСКИЕ БОЛЕЗНИПИЩЕВАРИТЕЛЬНОЙ СИСТЕМЫ БОЛЕЗНИДЫХАТЕЛЬНЫХ ПУТЕЙ БОЛЕЗНИКРОВООБРАЩЕНИЯ РАССТРОЙСТВАВ лекциях представлены сведения по основам клинической диагностики внутренних болезней