Obstructive sleep apnea (OSA) has long been associated with quantifiable retinal vascular changes that correlate with disease severity, according to an Australian research team. But the utilization of continuous positive airway pressure (CPAP) treatments to control OSA may also protect against progressive retinal arterial narrowing, says a report published in the Journal of Clinical Sleep Medicine.
In the prospective cohort study, investigators recruited adult patients undergoing diagnostic polysomnography at a tertiary sleep clinic. The patients were divided into 4 groups based on their apnea-hypopnea index (AHI); controls, mild, moderate, and severe OSA. The team recorded each patient’s static retinal vascular calibers (determined via fundus photos) and dynamic vascular pulsation amplitudes at baseline and again follow up approximately 24 months later. A proportion of patients (25) began CPAP therapy after baseline assessment.
Of the 79 patients who participated in the follow-up, 9 patients were in the control group, 18 patients in the mild OSA group, 21 patients in moderate OSA, and 31 patients had severe OSA. In the severe group, patients not on treatment showed progressive narrowing of retinal arteries from baseline, while those on CPAP showed a slight improvement (mean 171.3 μm to 65.1 μm and 171.2 μm to 174.0 μm respectively, P =.012). The investigators noted that the arteriovenous ratio was significantly reduced in the nontreatment group compared with the treatment group in severe OSA (0.836 to 0.821 and 0.837 to 0.855 respectively, P =.031). According to the findings, CPAP did not appear to have a significant impact on venous caliber or vascular pulsation.
This study has several limitations, including that CPAP treatment was offered to patients at their sleep physician’s discretion. As a result, there was no age or gender matching between groups. Also, there was a discrepancy in the proportion of patients who received CPAP between disease severity groups. Only 2 patients received CPAP in the mild group since it’s not routinely offered as first-line treatment to these patients. To increase statistical power, the mild and moderate severity groups were combined for data analysis. This may potentially obscure any differences in treatment response between these two groups. Additional compliance data were available for 20 of 25 (80%) of the patients in the CPAP group, but this data generally only dated back to a maximum of 12 months. And, most participants in this study who had hypertension were on anti-hypertensive treatment, which may improve retinal arterial narrowing. Lastly, this study only used quantitative parameters to assess retinal microvasculature.
Retinal vascular changes, such as arterial narrowing, have been associated with an increased risk of major cardiovascular events, including stroke. These changes could potentially be used as a surrogate biomarker of systemic cardiovascular risk in patients with OSA, according to researchers. However, more extensive studies are required for greater statistical power.
Wong B, Tong J, Schulz A, et al. The impact of continuous positive airway pressure treatment on retinal vascular changes in obstructive sleep apnea. J Clin Sleep Med. Published online February 3, 2021. doi:10.5664/jcsm.9118