![]() The instrument uses a coherent near-infrared probing beam (785 nm, 90 μW at the cornea) that conforms to the American National Standards Institute standard Z 136.1 for laser safety. 30 The blood flow measurement is obtained from the choriocapillaris layer behind the fovea, the superficial layer of the choroid with a dense network of capillaries. The LDF instrument used in this study to measure subfoveal choroidal blood flow (ChBF) has been described previously. 22 On the other hand, the abnormal postural behavior of intraocular pressure (IOP) changes has been described in patients with diabetes or systemic hypertension, 23 which are potential complications of OSA. However, its ability to autoregulate may be altered in smokers 19 and in patients with eye diseases such as age-related macular degeneration, 20 central serous chorioretinopathy, 21 and glaucoma. 18 Indeed, despite variations in systemic blood flow, choroidal blood flow is known to be autoregulated to maintain stable nutrition in the outer retina and to keep the temperature of the retina constant. 13 – 16 Body posture changes and isometric exercise are noninvasive methods for modifying blood flow to the eye, either after modification of gradient pressure between the heart and the eye (posture changes) 17 or after an increase in systemic blood pressure (exercise). 12 Contrary to the retinal and optic nerve head vasculature, choroid vessels are also subject to autonomic regulation. These experiments explored the mechanisms underlying hypercapnia-induced vasodilatation explained by a reduction in pH 11 and an increase in nitric oxide (NO) availability. 9 Our recent study on ocular microcirculation in OSA 10 with laser Doppler flowmetry (LDF) showed that OSA patients without cardiovascular comorbidities exhibited normal choroidal vasoreactivity in response to hyperoxia and hypercapnia. ( number, NCT00874913.)Īll these potential cardiovascular consequences associated with OSA may also interact with ocular vascular regulation, as suggested by the relation between OSA and nonarteritic anterior ischemic optic neuropathy, 7 central serous chorioretinopathy, 8 and glaucomatous optic neuropathy. This study strongly suggests that the regulation of choroidal blood flow, which depends on the orthosympathetic and parasympathetic systems, is unaltered in men with OSA who have no comorbidities. Choroidal blood flow responses to exercise and posture changes were unchanged after 6 to 9 months of continuous positive airway pressure treatment. In both populations, no significant change in choroidal blood flow or vascular resistance was found during the posture change. From the sitting to the supine position, a significant decrease in mean arterial pressure occurred in both groups (10.9%–13.4% P < 0.001). A significant linear relationship ( P = 0.0003) was noted between choroidal vascular resistance and the OPP changes during exercise in OSA patients and control subjects. ![]() Choroidal reactivity was assessed by laser Doppler flowmetry, which measured subfoveal choroidal blood flow.ĭuring exercise, blood pressure parameters increased significantly within the same range, with a similar profile over time in OSA patients and control subjects. All subjects underwent sleep studies and cardiovascular phenotyping (24-hour blood pressure monitoring, arterial stiffness measurements, and cardiac and carotid echography). Healthy men were matched 1:1 for body mass index, sex, and age with patients with newly diagnosed OSA without cardiovascular comorbidities. ![]() It was hypothesized that choroidal vascular reactivity in response to isometric exercise and posture changes could be altered in OSA patients. Exercise and posture changes can be used to manipulate blood pressure, ocular perfusion pressure (OPP), or both. Obstructive sleep apnea (OSA) syndrome generates hypertension, atherosclerosis, and endothelial and autonomic dysfunction, which may mutually interact with ocular vascular regulation. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |