Non-arteritic anterior ischemic optic neuropathy (NAION) generally appears in middle-aged adults, with an annual incidence between 2.3 and 11.4 per 100,000 people. It is characterized by sudden, painless, monocular visual loss with inflammation of the optic disc.
In general, there is no treatment and the visual prognosis is generally not good. Involvement of the paired eye has been reported in 12 to 15% over the next 5 years. Therefore, it is essential to know which risk factors can be controlled in these patients.
The most common risk factors are diabetes and hypertension, followed by hyperlipidemia, smoking, cardiac ischemia, and atherosclerosis. There have been some reports indicating that obstructive sleep apnea is also an independent risk factor.
Repeated episodes of apnea during sleep cause less oxygen saturation in the blood and this can affect different organs.
In the present study we carried out a nationwide investigation to determine the existence of an association between obstructive sleep apnea and the development of NAION.
Patients and methods: The present study used a cohort from the Korean National Health Insurance, which included 1025,340 beneficiaries, between 2002 and 2013. 919 patients with a new diagnosis of obstructive sleep apnea, over 40 years of age, were identified. and 9190 controls without apnea were used.
Propensity scores were used with respect to age, sex, demographics, comorbidities, and concurrent medications. Statistical studies were performed to determine the risk of developing NAION in patients with obstructive sleep apnea.
Previous studies suggested the association between obstructive sleep apnea and NAION. In the two previous studies of populations over 40 years of age, the incidence of NAION risk was relatively low compared to the present study and previous reports.
Perhaps it is because these studies did not cover low-income families, but rather people with fewer comorbidities and being treated for other disorders they may suffer from. In contrast, the cohort of the present study covers the general population of South Korea, making it more representative.
The underlying mechanism that increases the risk of NAION in patients with obstructive sleep apnea is unclear. One of the main causes is believed to be vascular dysfunction of the small vessels that supply the anterior part of the optic nerve and a structural factor of the optic nerve head, a small disc.
Hypoperfusion has been suggested, but previous studies observed that ocular perfusion pressure does not decrease significantly at night in cases of NAION. Apnea or hypopnea during sleep can cause sympathetic activation and release of vasoconstrictor substances that cause an increase in blood pressure.
Treatment of OSA depends on the severity of the sleep apnea. Mild cases are treated only with weight loss, avoiding alcohol and sleeping in a lateral ulna position, moderate to severe cases are treated with continuous positive airway pressure.
Despite the existence of some studies, it has not been possible to determine whether the severity of obstructive sleep apnea and the type of treatment could affect the risk of NAION.
The results of this study should be interpreted taking into account some limitations.
| Conclusions |
Patients with obstructive sleep apnea are at increased risk of developing NAION, although the absolute risk is low.
Although the preventive effect of treatment against obstructive sleep apnea on NAION is not clear, adequate evaluation of obstructive sleep apnea using polysomnography and its treatment with lifestyle modification considering the risk of NAION is recommended, at least until that new evidence emerges indicating the need for change in clinical practice guidelines.
