Asanas and intraocular pressure

Safety is a crucial part of yoga practice and teaching. We are aware of the precautions on hypertension, diabetes, cancer and injuries. But the increase of intraocular pressure during head down poses is not widely known.
Just like blood pressure, there is pressure inside of our eyes, namely intraocular pressure (IOP) to maintain the physical shape and functions. If the pressure keeps in a higher than normal level (21 mmHg), the optic nerves might be damaged permanently, resulting in Glaucoma. Though there is also normal tension glaucoma, meaning that the optic nerve is damaged in the eye with normal intraocular pressure. The majority of glaucoma patients have high IOP and the only treatment is to use eye drops to lower the pressure.
A research indicated that there was around 10 mmHg increase on IOP after holding the head down poses (Ahdo Mukka Svasana, Halasana, Utasana and Viparita Karani) for 2 min (Jasien et al, 2015), in both healthy adults and glaucoma patients. Though the pressure returns to baseline level within 2 min, the long term effect of the IOP rush in those head down poses is still unknown. The tricky thing about glaucoma is that it is usually asymptomatic until very late stage. Therefore, students in the yoga class may not know they have glaucoma even if they do.
The most likely type of glaucoma we may encounter in yoga class is acute angle closure glaucoma. The anterior chamber angle closes, resulting in drastic increase of the IOP. The symptoms include severe eye pain, blurred vision or seeing halos around light, headache, nausea and vomiting.
To teach safely, we should always inquire our students for medical conditions and remind them to stop the poses in case of any discomfort. If we really encounter a student suffers from acute angle closure glaucoma during the class, do not panic and seek medical attention immediately. Lastly, make sure that we practice with professional indemnity.
1. Jasien JV, Jonas JB, de Moraes CG, Ritch R. Intraocular Pressure Rise in Subjects with and without Glaucoma during Four Common Yoga Positions. Lin H, ed. PLoS ONE. 2015;10(12):e0144505.
Carina Wang
YTT 200, Sep 2017

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