In a clinical setting, the Valsalva maneuver—induced with a forceful exhalation into a tube for 15 seconds—can arrest episodes of supraventricular tachycardia or can help identify certain cardiac abnormalities.1,2 However, complications are possible when the maneuver is performed either too forcefully or for too long.3 To better understand the maneuver’s ocular effects, a study based in China analyzed changes in IOP, Schlemm’s canal, autonomic nervous system activity and iridocorneal angle morphology in healthy individuals during the four different phases of the maneuver. Phase 1 encompasses the initial straining, phase 2 is the maintained strain of 15 seconds, phase 3 is the release and phase 4 is the return to normal heart rate.

The researchers found that heart rate, IOP and pupil diameter decreased significantly from phase 2 to phase 4, which may be related to changes in the autonomic nervous system, blood flow and ocular anatomy.4

After measuring 29 young, healthy individuals at baseline, phase 2 and phase 4 of the maneuver, the study found that, in phase 2 compared with baseline, heart rate variability, IOP (15.1±2.7mm Hg vs. 18.8 ± 3.5 mm Hg), mean area of Schlemm’s canal (7712.112µm2 vs. 8921.12μm2) and pupil diameter increased significantly, whereas iridiocorneal angle parameters decreased significantly. In phase 4, diastolic blood pressure, mean arterial pressure and the iridiocorneal angle parameters were significantly lower than baseline value, while pupil diameter and high frequency of heart rate variability were remarkably larger than baseline.

Their results lead the researchers to suggest that the expansion and collapse of Schlemm’s canal in different phases of the maneuver may be caused by changes in autonomic nervous system activity, while the maneuver’s effect on IOP may relate to changes in blood flow and ocular anatomy. Also, a significant increase in the low/high frequency of heart rate variability ratio in phase 2 might reflect an increased sympathetic activity, and the significant increase in high frequency indices in phase 4 reflect parasympathetic hyperfunction.

“Changes caused by the Valsalva maneuver in healthy young individuals may carry no clinical significance, although for patients with high risk factors of glaucoma, we suggest avoiding repeating the maneuver in daily life,” the researchers wrote.

1. Smith G. Management of supraventricular tachycardia using the Valsalva manoeuvre: a historical review and summary of published evidence. Eur J Emerg Med. 2012;19(6):346-52.

2. Rolandi M, Remmelink M, Nolte F, et al. Effect of the Valsalva maneuver on cardiac-coronary interaction assessed by wave intensity analysis. Conf Proc IEEE Eng Med Biol Soc. 2010:2010:3776-9.

3.Kabat AG, Sowka, JW. Don’t hold your breath. Rev Optom. 2012;149(6)116-20.

4. Sun L, Chen W, Chen Z, et al. Dual effect of the Valsalva maneuver on autonomic nervous system activity, intraocular pressure, Schlemm's canal, and iridocorneal angle morphology. BMC Ophthalmol. January 3, 2020. [Epub ahead of print].