This is a question from a reader who, sitting at a table, sees with peripheral vision the rapid up and down movements of a table lamp. And the same thing happened with him with different things a couple of times a week.
Well, I'm not an ophthalmologist, and I have three explanations: simple, my own, and complex.
Simple explanation
We have light-sensitive cells in our eyes called rods and cones. The rods are very sensitive, located on the periphery of the retina and do not distinguish colors. With chopsticks we see at dusk.
The cones are grouped in the middle of the retina, their sensitivity is not very high, and they distinguish colors.
So those very sticks on the periphery clearly distinguish frequent color fluctuations. The cones in the center can't do that.
Electrical light sources around us often flicker in time with the alternating current in the electrical network. The current in the wires changes direction 50 times per second.
It turns out that if the lamp flickers, then we will rather notice it with peripheral vision.
It makes sense that the lamp manufacturer won't let it flicker head-on. Otherwise nobody will buy the lamp. But if you try very hard, you can notice these flickering with peripheral vision.
Sometimes we can see lamps flickering even with cones. To do this, each flash must be stretched.
Mirror
Did you do such an experience at school in physics lessons?
Stand with your back to night lights, lanterns and cars. Take a mirror in your hands and rotate it around so that the reflections of the lanterns turn into glowing arcs and circles. Some of these arcs will be solid. This is how incandescent lamps shine. And some will be dotted. These are individual flashes of flickering lamps, which we stretched out with a mirror.
In fluorescent lamps like street lamps, the light consists of rapid flashes. Dotted lines are obtained from them.
In old car headlights, the light is generated by incandescent bulbs. If the thread of this lamp is heated and lit up, then it cannot go out in a split second. It will slowly fade out. Such lamps give a reflection of solid continuous luminous circles and arcs.
Most likely the reader has just such an effect. That is, with peripheral vision, he sees the flickering of a table lamp in time with the alternating voltage in the electrical network.
My own explanation
I have a migraine with ciliated scotoma. This is such a shimmering spot before the eyes. Once a year, it appears in my field of vision, in 30 minutes it gradually expands and creeps to the periphery. So when the remnants of this scotoma have almost crawled away, the flickering is still visible with peripheral vision. Moreover, the sticks do not matter here, because the flicker is formed in the occipital cortex of the brain. These scotomas do not have to be always bright and understandable. They are sometimes noticed as faint flickering in the periphery.
Complicated explanation
In addition to ciliated scotoma, there are actually all sorts of twitching of the eyeballs, which are called nystagmus. When our head is spinning, then we see the movement of surrounding objects, but an outside observer, looking to in our eyes, with horror he will notice how our eyeballs shake finely in the vertical direction, horizontally or even circles. A neurologist deals with these matters, and there are a lot of different reasons.
And the ophthalmologist also has many complex explanations for flickering in the eyes, so if this thing interferes with your life, then contact a specialist.
