I am afraid of the eyedoctor; I haven't seen one for at least a decade, maybe longer. I've been practicing yoga for 9 years. This could be a problem. Here is why I'm vowing to make an appointment soon.
Glaucoma affects 15% of people in their 60s and up. This disease creates irreversible vision damage due to increased interocular pressure pressing on the II cranial nerve which supplies your retina. Inversions, all of them, including downward facing dog and child's pose, can increase interocular pressure and aggrevate glaucoma. You would think that the solution is just to not practice asanas with your head lower than your heart if you have glaucoma, and you're right. Except, many people that have glaucoma don't know it until big damage has been done. The disease starts by gradually eliminating your peripheral vision, you really don't see it coming. The only way to find out is to have an eye exam by a professional.
Who is at risk?
*African Americans 35+
*People with a family history of glaucoma
*People with cardiovascular disease
*People with hypertension
*Those that experience vasospasms
*Likely at risk people: migrane sufferers, the obese, smokers, heavy alcohol users, those with anxiety or high stress levels
I would like to hypothesize that regular yogasana practice including inversions would help your body to learn to control and tolerate increased interocular pressure. However, I could find no research to support that hypothesis. On the bright side, there is also no evidence that yogis have a higher glaucoma rate.
The Mayo Clinic lists weight & blood pressure control and excerise as good prevention, all of which yoga practice provides.
They also recommend eye exams every 3-5 years, every year if you're over 60. I'm clearly due. The good news is the reason I dislike eye exams is the air-puff glaucoma exam. Apparently, this went out of style years ago and now a more accurate, non-air-puff test is used. Nothing should hold me back now.
What do I recommend for the inversion-loving yogi?
1. Get regular eye check-ups.
2. If you have glaucoma, follow doctors orders and practice ahimsa by modifying your asana practice appropriately.
3. If you are a yoga teacher, teach inversions with great reverence and perhaps encourage your students to love their drishti with a eye check-up.
A side note: Corticosteroids, especially those in eye drop form can increase interocular pressure. The effect can last a few weeks to months after you are off the drug. If you are on these drugs for any reason, it may be wise to modify your practice until this time period passes.
Appropriate asana practice modifications would be to keep your head above your heart as much as possible and definitely no shoulder, head, or hand-stands. Perhaps prop your head on a folded towel for legs up the wall instead. Make your backward bends all ones that start from the belly down position. Spend little if any time in standing forward folds and downward facing dog; instead practice your forward folds seated. Get creative and protect your drishti!