Choroidal Blood Flow Response to Hyperoxia and Hypercapnia in Patients With Obstructive Sleep Apnea Syndrome

Abstract

Purpose: : Obstructive sleep apnea syndrome (OSA) is 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 hyperoxia and 8% CO₂ breathing in OSA patients, as compared with matched healthy control subjects.

Methods: : Eighteen 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 hyperoxia and hypercapnia (8% CO2) inhalation.

Results: : OSA patients exhibited a similar choroidal reactivity during hyperoxia (stability of choroidal blood flow) and hypercapnia (1.5% increase in choroidal blood flow per 1 mmHg PtCO₂) than controls.

Conclusions: : This prospective comparative study explored for the first time the choroidal blood flow of OSA patients and results showed that subfoveal ChBF reactivity to gas in OSA patients is similar to healthy control subjects. These preliminary results suggest that choroidal vasculature is protected against the inbalance between the vasodilation (NO) and vasoconstriction (endothelin) system.

Keywords: choroid • blood supply