Why do I get light-headed when watching TV shows or movies?

You really should go to a doctor. Like. really. If it's common and you don't have a clear "its this" (like standing up suddenly, or some other condition you know about,) Sudden lightedness that comes and goes could be one of several awful things.

(or it could totally something not scary at all.)

We're not doctors... (and honestly, it's not stupid to ask a doctor this. but it is kinda stupid to ask randos on the internet. thats how you wind up snorting ground up leeches or something weird.)

WebMD says it's a brain tumor. Or an ear infection. Or lupus. But it's almost never lupus.

Another option is seizures from strobing lights. See a doctor.

My guess would be motion sickness.

I am not a doctor.

Q: physically, how are you watching them? On a couch? Lying in bed? Hunched over on the bus? Phone? TV? Do you have auto motion plus enabled (you monster)? Do you watch it in one place? Has that room been checked for carbon monoxide? Is it a basement? Has it been checked for radon?

It could be a lot of things and there's not enough information provided but the first thing that occurred to me is blood pressure. Do you have a blood pressure cuff? Try to use it when you're feeling light headed and when you're not and comparing numbers.

It could be a physical things about the position of your body, pressure on something because you're hunched over or something. It could be a visual things too. There are conditions where moving/changing visuals could affect you.

It's kind of overwhelming all of the things it could be and you really should go to a doctor.

While you're waiting for your appointment try to make observations about what is the same about reading vs watching and what is different. This will help them figure out what to investigate.

On all screens? All movies and all tv? Is this with a new tv? When you go to the movies with a projector too?

Try changing the tv setting to "movie mode" or "cinema mode". You can google for the difference it gives.

Could be motion sickness.

Is it recent and only with some TV's or maybe with a new one you bought. If so its possible changing some settings will make it more palatable. Apologies but I really don't know about this stuff as I have not messed around with configs but I have seen a variety of stuff around modern tvs and settings. In particular I found out why my work tv gave me a creep uncanny valley sensation compared to my home one.

It is probably some issue your body has with lights.

It could be something as harmless as being photosensitive or motion sickness. It could be completely benign and you might live for years with this one weird quirk.

You could also be having seizure auras, small strokes, having a psychotic break, or something else out of 500 other possibilities of things that will hurt, kill, or just generally terrorize you for years to come if not treated.

Go to a doctor. I would start with a neurologist, but depending on your locality and if you do or don't have health insurance you may need to see some kind of generalist first like a family medicine doctor/general practitioner. There's also a lot of overlap between them and urgent care clinics these days. You would just ask if they can write you a referral.

I know, for instance, American health insurances sometimes won't pay for a specialist visit until a family medicine doctor/General practitioner says it's fine because somehow having to see two doctors is more efficient and saves more money. I've given up on sense in such things. My faith in the system finally took its last breath when I drove my fiance two hours to try to get insurance to cover a test and several hours of bureaucratic nonsense later they still wouldn't pay. At the time he had medicaid, which in our state is overseen by a branch of one of the state's existing Healthcare insurance companies. (You get one randomly assigned but you can change it if you fill out a really long form and get it mailed in within 90 days or manage to log into the website that only works when Jupiter's in the fifth house). Does that sound corrupt as fuck? It really, really is.

My fiance needed a specific test, and the insurer said we needed to get it done through his primary care physician and said the preassigned one was on the back of the insurance card that my fiance had gotten a year or so before when he successfully qualified for medicaid. We could also call and have the primary doctor changed... after finding a primary care physician who could afford to take new medicaid patients! (ha)

Anyway so the preassigned doctor was two hours away from my fiance's home address, which was still the same from when he had applied and qualified. I figured they just didn't have any doctors who would take medicaid that were closer. I thought maybe that was just me being pessimistic, but no. American insurance companies have a gift for malignant apathy. My assumption that they just didn't care was disturbingly generous. No, they were actively fucking me with the apathy. It sounds impossible, but American insurance companies are out there braving new frontiers of malicious apathy every day!

When we arrived, the receptionists informed us that this doctor had not taken medicaid in years as in multiple as in before the Medicaid distributor had ever printed the card. They apparently had a list somewhere of doctors that at some point in the last decade had taken medicaid, and they were just scrolling down the list assigning them at random. And they were never calling anyone to see if they still took their insurance or, I don't know, checking it against their own fucking books.

And again, you WANT to think it's apathy and it probably is at the low levels like claims and customer service representatives. They probably beat the empathy out of those workers. But the company is taking a government check for each medicaid recipient under their domain and flossing their asscracks with the money. Then the recipients eventually give up on navigating through 15 pages of a cyberpunk DMV of a website with a sitemap that's inscrutable to anyone but the highest of bureaucrats and a phone tree where when you get a human to talk to they fill out the same form again and give you a case number that the next person you talk to will have no idea what to do with.

...and then they just get to keep the money that they were supposed to be using to get people healthcare. They provide less care, and they get to keep more money. They literally net MORE money the worse and harder to use their product is. The only thing middlemen have going for them is to maybe provide convenience and they've still figured out how to make more money from having the least convenient product. And Medicaid patients who can't afford to drive far, or a lawyer, or even to just miss a day at work, make GREAT targets. Add a mental illness into that mix, the kind that are way more likely under the stresses of poverty and also way more likely to lead to it. The mentally ill aren't dumb, but executive dysfunction is a motherfucker. Put a few forms and phone calls between them and mental health professionals? You just eliminated most people with anxiety.

Get money -> frustrate people into not making them spend it on Healthcare.

Infinite money glitch.

Need more details. What are you watching when it happens? Or are you saying if you watch CSI, Sesame Street and a David Attenborough documentary about ants back to back you'd get light-headed 3 times, once during each?

As ValiantDust said it could just be motion sickness depending what it is you're watching.

See a doctor.

But it might be worth buying a machine to check your blood pressure (they're not terribly expensive) because it's hard to capture it in the doctor's office. Take a measurement or three before you feel light-headed, keep the cuff on and take more measurements when you start to feel light-headed. Keep a record of the measurements (and how you were feeling at the time) to help your doctor rule blood pressure in or out as a cause.

Put. Down. The. Bong.