martin A reference I found that reviews this and a lot of other older evidence about flicker and pattern sensitivity is from Arnold Wilkins - link below (see section 2.2.3 on p. 21). It looks like the original study of covering one eye for epilepsy is Jeavons and Harding (1975) who saw in epilepsy in EEG tests of flicker photo stimulation, that covering one eye stops the convulsive response to flicker in 164 of 244 patients (67%), reduces the convulsive response in 75 others (31%), and 5 (2%) showed no difference in response between monocular and binocular vision. I haven’t read the original reference- I couldn’t easily find it online.
So the above implies that covering one eye is helpful for most epilepsy patients encountering flicker, and may protect many. However, the above study was a lab test of limited duration, so it isn’t clear that it would be completely preventative for some patients in real-life longer-lasting situations. And I’d really like to see the data and study design in the original paper before concluding too much.
Wilkins, A.J. (1995) Visual Stress. Oxford University Press. 194 pp. http://www1.essex.ac.uk/psychology/overlays/book1.pdf Warning: This book contains multiple patterns that may bother sensitive individuals. The book warns those with epilepsy and migraine not to look at the frontispiece. Patterns in the book triggered my "LED" symptoms when I ignored the warning.
The Wilkins review also talks about reading masks that partially obscure vision that help prevent seizures in a patient with pattern sensitive epilepsy (see section 5.5 on p. 75). There’s another Wilkins 1980 paper “Visually Induced Seizures” that says glasses with one frosted lens reduced seizures for 2 patients with pattern sensitive epilepsy.
For migraine, I can’t remember reading about binocular vs monocular vision and flicker, but I’ll look out for it. I review the literature on migraine and flicker here - and all of these studies are for fairly slow flicker, not for the 100-120Hz flicker most common in LED lighting (there’s no migraine studies for that): https://www.flickersense.org/background/health-effects-of-led-lights-and-screens/flicker-below-100-hz-scientific-literature
I can say as a migraine patient who is also sensitive to flicker and repetitive patterns, that none of my neurologists ever suggested that I try patching an eye, so I’m not sure that it’s a common recommendation in practice. I figured out on my own that for screen use, patching makes my flicker symptoms start slower, but doesn’t prevent them. When I briefly walk through an area with flickering LED light, I wear a hat, Shade 5 welding glasses, keep one eye closed, and close the other eye as much as possible - and this is only OK-ish if the flicker is fairly mild and the exposure is brief. If I completely avoid flicker, I’m totally fine health-wise. I just had brief migraine headaches maybe a few times a year prior to first getting flicker symptoms in 2018.
I have no eyestrain, no eye muscle involvement, and no convergence insufficiency or other BVD (confirmed by a BVD expert). Just nearsightedness. When in flickering LED light I feel sharp vibrating spikes of pain in the tissue behind my right eye and/or spatial disorientation/motion sickness/nausea. Starting about 30-45 minutes after a flicker exposure, painful pressure will become noticeable in my right temple and increase over the course of hours to weeks, depending on the severity of the flicker. A neuroophthalmologist found right side peripheral blindness due to the flicker of the new LED office lights which triggered several days of symptoms. The peripheral blindness was absent in a later visit where I protected my eyes from the office lights. Moderately bad events trigger severe impairment of working memory, brain fog, and extreme fatigue and subtle postural issues - more brain fog if sitting up. Often I’ll also get a left-side migraine headache exacerbated by light brightness during the migraine with vomiting about 2-4 days after the flicker. The migraine may last a few hours. I also have painfully sensitive spots on the right side of my scalp following moderate flicker exposure. Somewhat worse flicker incidents also cause severe spatial disorientation, nausea, loss of appetite, inability to balance with eyes closed, and insomnia. My worst episode, 3 hours in flickering LED lighting (mostly 10% flicker, but some 100%), caused symptoms lasting many months. In this episode, when the swelling in the right side of my head was at its peak a couple weeks later, my eyelid was swollen and one day it was hard to move my eye in its socket due to what felt like swelling, but other than that, I’ve never felt eyestrain.