Like if you have blurry vision, and you don’t wear vision-correcting glasses, does that set off an inevitable downward spiral of degradation of your vision?

Not really. It depends on how bad. But not having good eyesight which leads to blurry vision isn’t a blanket condition, in that, your entire world isn’t just a blur. You can focus on some things (far sighted vs near sighted) and even if you can’t see well close-up, you can still force your eyes in some circumstances to produce better vision if you put in effort. It’s like trying to lift a bag that’s too heavy for you. You may not be able to get it above your head, but maybe you can lift it off the floor if you try hard enough.

What causes an inevitable degradation is more to do with age and how our bodies just fail over time. Headaches and other ailments associated with poor vision are the number one cause for most people to see an optometrist. Your eyes can only handle so much load before it takes a toll. Which should be the red flag for you and your “blurry” glasses.

Closing your eyes is the most ideal because it cuts off sensory information, which saves energy (your sensory and motor cortex are spared or operate with less resources). It’s like lying still vs running a marathon. It requires a lot of energy for your brain to continually process info. And humans are visual creatures. We take vision above all else. If it looks like a duck, but sounds like a sheep and smells like bread, it’s still a duck to us. Which tells you just how much of our brain is carved out for that sense.

Baggage checkers at airports that sit behind the x-ray machine usually lose sharpness after about 30m (which means they can allow potentially dangerous objects onto aircrafts). Attention is super expensive and if you call on someone’s total, undivided attention, that can only be maintained for so long before the brain sort of checks out.

And not it’s not a dumb question.

gila@lemm.see answered your question below regarding simulated blurriness and I added a bit to it if you want to read more.