Retinal arteriolar narrowing may occur with increasing OSA severity
Increasing obstructive sleep apnoea (OSA) severity appears to have an independent association with retinal arteriolar narrowing and attenuated vascular pulsation amplitude, with the retinal vasculature a potential surrogate biomarker of cerebral and systemic vascular risk in patients with OSA, according to a study.
The prospective cross-sectional study included 115 adult patients (mean age 58 years; 63.5 percent male) undergoing diagnostic polysomnography studies at a private Australian university teaching hospital. Patients were grouped according to severity of OSA, as defined by the apnoea-hypopnea index (AHI): severe (>30; n=41), moderate (>15 to 30; n=35), mild (5 to 15; n=25) and controls (<5; n=14).
Static retinal vascular calibre was calculated as the average diameter of retinal arterioles (CRAE) and venules (CRVE), and summarized as the arteriovenous ratio (AVR). On the other hand, dynamic retinal vascular calibre was measured as the average pulsation amplitude of retinal arterioles (SRAP) and venules (SRVP). Multivariate linear regression analysis was used to perform comparisons across groups. Factors such as age, body mass index and mean arterial pressure were included as potential confounders.
Increasing AHI was found to be significantly associated with decreasing AVR (p=0.008) and CRAE (p=0.016). Increasing AHI was also related with attenuated retinal vascular pulsation amplitude (SRAP, p=0.028; SRVP, p<0.0001).
Characterized by repeated episodes of partial or complete closure of the upper airway during sleep, OSA has been reported to be an independent risk factor for obesity and hypertension, with severe OSA increasing the chance of fatal and nonfatal cardiovascular events. [Am J Cardiol 2007;99:1298-302; Lancet 2005;365:1046-53]
Retinal vessel, on the other hand, is said to have a similar anatomy, physiology and developmental characteristics with the coronary and cerebrovascular system. Retinal vascular abnormalities may occur prior to cardiovascular and cerebrovascular diseases, serving as a predictive marker for the occurrence, clinical course, and prognosis of cardiovascular and cerebrovascular diseases. [Hypertension 2008;51:119-26; J Anat 2005;206:319-48; Chin Med J (Engl) 2017;130:805–810]
Moreover, the retinal vasculature can be viewed noninvasively, and recent advances in retinal imaging have allowed quantitative measurement of retinal microvascular calibre in large epidemiological studies, which have in turn shown that retinal arteriolar diameter is predictive of diabetes mellitus, hypertension and cardiovascular disease. [Surv Ophthalmol 2009;54:74-95; Arch Intern Med 2005;165:1060-5; Am J Epidemiol 2009;170:1323-32; Atherosclerosis 2013;226:124–128]