Nocturnal hypotension, sleep apnea, and ocular perfusion: continuous monitoring studies

This audio article is from VisualFieldTest.com.Read the full article here: https://visualfieldtest.com/en/nocturnal-hypotension-sleep-apnea-and-ocular-perfusion-continuous-monitoring-studiesTest your visual field online: https://visualfieldtest.comSupport the show so new episodes keep coming: https://www.buzzsprout.com/2563091/supportExcerpt:Introduction Our eyes depend on a steady blood flow and pressure balance to stay healthy. During sleep, changes in blood pressure, breathing, and even eye pressure can affect vision. In particular, a drop in blood pressure at night (nocturnal hypotension) and episodes of stopped breathing (sleep apnea) may reduce ocular perfusion pressure – the difference between blood pressure and eye pressure – and stress the optic nerve. Researchers are now using 24-hour monitoring of blood pressure, oxygen levels, and eye pressure to see how these factors line up with subtle changes in vision. This article explains how nighttime blood pressure dips and sleep apnea can influence eye health, how we can measure them, and what can be done to protect the eyes. Nighttime Blood Pressure Dips and Eye Health Most people experience a normal “dip” in blood pressure during sleep – typically a 10–20% fall compared to daytime levels. However, some individuals, especially those on blood pressure medications, experience a larger drop. When blood pressure falls too far, the ocular perfusion pressure (OPP) can become too low. The OPP is essentially the driving pressure pushing blood into the eye (roughly blood pressure minus eye pressure). If OPP drops too much, the optic nerve may not get enough blood. In fact, experts believe that the balance between intraocular pressure (IOP) and blood pressure is key to optic nerve health (). Studies confirm the danger of extreme nighttime dips. For example, glaucoma patients whose blood pressure fell far below daytime levels at night tended to have more progression of vision loss. In one long-term study of normal-tension glaucoma patients, the duration and magnitude of nocturnal blood pressure below daytime pressure predicted the rate of visual field loss (). In practical terms, this means if your nighttime blood pressure stays significantly (e.g. 10 mmHg or more) below your daytime average for many hours, your risk of glaucoma worsening is higher. Another study found that glaucoma patients who had unusual large dips in night blood pressure (so-called over-dippers) showed larger swings in ocular perfusion pressure and worse visual field test results (). Importantly, body position and sleep also matter. Normally, when you lie down, intraocular pressure (IOP) tends to rise (by 10–20%) because eye fluid drains more slowly (). So at night you may have higher IOP and lower blood pressure at the same time – a “double whammy” that can lower OPP. In simple terms, the nighttime balance of pressures can leave the optic nerve vulnerable if blood pressure drops too much or eye pressure rises too much. Sleep Apnea and Oxygen Supply Obstructive sleep apnea (OSA) is a condition where the upper airway repeatedly collapses during sleep, causing breathing to stop briefly and oxygen levels to fall. During an apnea event, the body may experience low oxygen (hypoxia) and sudden surges in blood pressure when breathing resumes. Over time, untreated sleep apnea has many health effects, including on the eyes. Research shows that patients with glaucoma have a higher chance of having sleep apnea. For instance, one study found 20% of glaucoma patients screened positive for sleep apnea (higher than in similar people without glaucoma) (). A large meta-analysis reported that sleep apnea is significSupport the show