Possible association between obstructive sleep apnoea and development of normal tension glaucoma

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Possible association between obstructive sleep apnoea and development of normal tension glaucoma


Author: Chong, Sze-lok Gabriela
Title: Possible association between obstructive sleep apnoea and development of normal tension glaucoma
Degree: D.H.Sc.
Year: 2011
Subject: Sleep apnea syndromes
Hong Kong Polytechnic University -- Dissertations
Department: Faculty of Health and Social Sciences
Pages: 169 leaves : ill. (some col.) ; 30 cm.
InnoPac Record: http://library.polyu.edu.hk/record=b2417680
URI: http://theses.lib.polyu.edu.hk/handle/200/6124
Abstract: Background: An association of obstructive sleep apnoea (OSA) and glaucoma has been widely reported, and has aroused concern in sleep medicine specialists and ophthalmic professionals. OSA is a condition where respiration during sleep is punctuated with repetitive cyclical pauses causing transient alterations in both sympathetic and parasympathetic activity. These autonomic changes may be a mechanism for the association between OSA and normal tension glaucoma (NTG). Aims: The aim of this study was to explore the possible association between OSA and development of NTG. Heart rate variability (HRV) alterations and the relationship of autonomic control in OSA patients with and without NTG were investigated. Methods: In this study, two groups of patients were studied: OSA patients with NTG, and OSA patients without NTG. Sixty-two patients (57 males, 5 females) aged between 30 and 65 years and with medically confirmed OSA were recruited through years 2008-09. After screening for fulfilling the selection criteria and consent being obtained, an overnight polysomnography (PSG) study was arranged for each subject. An ophthalmological examination for diagnosing of glaucoma then followed. In the analysis, the ECG signals in the period of OSA and normal sleep were extracted respectively, all artifacts were eliminated. HRV parameters were extracted from ECG tracing by spectral analysis. Three HRV parameters [low-frequency (LF), high-frequency (HF) and LF/HF ratio] were used to indicate the autonomic function in the two study groups.
Results: Forty-eight eyes of 48 OSA patients met the inclusion criteria. Half of the patients were newly diagnosed and untreated NTG patients. A high incidence of NTG was found in patients with severe OSA. OSA patients with NTG demonstrated higher LF values and significant higher LF/HF ratio during sleep compared to those without NTG, suggesting that sympathetic tone was elevated during sleep. The result of logistic regression analysis showed that LF/HF ratio was a significant predictor to indicate the disturbed autonomic activity in OSA patients with NTG, suggesting that systemic indicators of autonomic dysfunction are features of OSA patients exhibiting NTG and may be linked to the onset and/or further progression of the disease. Wider elevated amplitudes of ocular perfusion pressure (OPP) and mean arterial blood pressure (MAP) were found in OSA subjects with NTG, indicating that the autoregulatory mechanism may be defective in eyes during sleep. The increments in amplitude of OPP and MAP were significantly associated with the severity of NTG. Moreover, a significant reduction in MAP and OPP was shown in the supine position, which may increase the potential for tissue hypoxia in OSA patients. Conclusion: The present study suggests that increasing severity of OSA may constitute a high-risk population for NTG. Patients with severe OSA may be highly at risk for NTG, and should be screened for the ocular conditions and, if necessary, be treated to avoid further deterioration of their vision. OSA subject with NTG can be characterised by autonomic dysfunction, which is expressed as high sympathetic activity. An increment in OPP and MAP measured on awakening, and nocturnal supine body position may also play a role in the multi-factor process of developing NTG in OSA patients.

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