Choroidal blood flow response to isometric exercise in patients with obstructive sleep apnea syndrome.

Purpose Obstructive sleep apnea syndrome (OSA) has been recently reported to be associated with ischemic and glaucomatous optic neuropathy. The physiopathology of these diseases includes an abnormal regulation in the optic nerve head vasculature. The aim of our study was to characterize the choroidal vascular reactivity to acute increase in ocular perfusion pressure due to exercise in OSA patients. Methods Fourteen newly diagnosed OSA patients were included in this prospective study. Control subjects were matched with OSA patients for body mass index (BMI), gender and age. At the screening visit, each subject underwent a general exam, cardiovascular, neurologic and ophthalmological examinations, and underwent complete overnight polysomnography. The LDF instrument used in this study to measure subfoveal choroidal blood flow (ChBF) measured the following parameters: ChBVel (kHz); volume, ChBVol (in arbitrary units, AU) and the relative flow, ChBF = ChBVel  ChBVol (in AU). Vascular choroidal reactivity was tested during squatting. Results OSA patients exhibited a similar choroidal reactivity during increase in OPP (i.e. stability of choroidal blood flow) than controls until an increase of OPP about 145%. We found a similar vascular resistance increase in both groups during increase of OPP. Conclusion This prospective comparative study explored for the first time the choroidal blood flow of OSA patients and showed that subfoveal ChBF reactivity to gas in OSA patients differed from that of healthy control subjects. These preliminary results suggest that choroidal vasculature of OSA patients remained vasoconstricted when OPP increased, due to a chronic sympathetic activation.