Untreated sleep apnea may increase risk of optic nerve damage

Use of continuous positive airway pressure as a treatment for sleep apnea has been implicated as a cause of elevated IOP and has been questioned as an effective means of preventing optic neuropathy. However, other studies recommend using continuous positive airway pressure to prevent glaucomatous or ischemic optic neuropathy. This study used a large, national cohort to compare the incidence of glaucomatous and other forms of optic neuropathy among individuals with and without sleep apnea and to assess whether the hazard for these conditions is associated with sleep apnea or its treatment, continuous positive airway pressure.

Investigators reviewed billing records from 2001 through 2007 for a large U.S. managed care network to identify beneficiaries 40 years of age and older. Among the 2,259,061 individuals included in the study, 156,336 (6.9 percent) had one or more sleep apnea diagnoses. The risk of open-angle glaucoma was no different among persons with sleep apnea either treated or untreated with continuous positive airway pressure and individuals without sleep apnea. Similar findings were observed when assessing the risk of normal-tension glaucoma.

However, the investigators found a significantly increased risk of nonarteritic ischemic optic neuropathy (NAION) (HR, 1.16) and idiopathic intracranial hypertension (IIH) (HR, 2.03) in those with sleep apnea who were not receiving continuous positive airway pressure therapy compared with individuals without sleep apnea. Treated sleep apnea patients did not show this increased risk.

The authors say the possible mechanism by which sleep apnea is related to IIH is not clearly known. It has been proposed that patients with sleep apnea experience nocturnal episodes of hypercapnia that can lead to increased intracranial pressure and secondary papilledema. The termination of each individual obstructive apnea during sleep generally is associated with a marked although transient spike in intracranial pressure, possibly in association with increased systemic blood pressure, heart rate and sympathetic tone. Episodes that are repeated hundreds of times each night, as often happens in sleep apnea, conceivably could contribute to, or exacerbate, IIH.

They conclude that if additional studies confirm these findings, it may be worthwhile recommending that newly-diagnosed sleep apnea patients undergo ophthalmologic examination with careful evaluation of the optic nerve to assess for these vision-threatening disorders. It is common for patients with IIH to be overweight or have increased body mass index, but in patients with NAION this is certainly not always the case. In NAION patients without an underlying etiology, such as hypertension or diabetes, it may to reasonable to inquire about sleep apnea as a possible risk factor.