Welcome to Paging Dr. Gupta. Thanks so much for joining us. It is the week of July 4th. Summer is in full swing. The season is heating up and you've had a lot of related questions. You know, I love these episodes because they're all about you. And I get a chance to hear about the concerns that you have that you're living through right now. So let's get straight into it. Kyra's back with us. Who do we have first?

All right, hey Sanjay. So our first question today is coming from a listener in Philadelphia. And as you just said, Summer is officially here. I feel like this question has gotta be on a lot of people's minds. Take a listen.

Dr. Gupta, my name is Deirdre. A friend of mine said that a doctor told her that our eyes should get a certain amount of unfiltered sunlight per day. And I was really surprised because I've had an eye doctor tell me to wear sunglasses all the time. But yeah, what's the truth to, you know, sort of like how you get 10 minutes of sunlight on your skin without sunscreen? I just, I just can't believe it. So Dr. Gupta, what do you say about the sunlight and the eyes? Uh, thanks so much.

Okay Kyra, thank you, and Deirdre, that is a great question, honestly something that I've thought about myself, a lot of people have been wondering about, and I'm going to give you as detailed an answer as I can in just a minute.

Let me start by this, there is some confusion I think overall just when it comes to sunlight and your eyes. So one of the things I get to do on this podcast is call people who are the world experts in these various areas, world experts who can come on the podcast to help answer your questions. So we called up Dr. Raj Maturi, he's an ophthalmologist, he's got 25 years of experience, he's also a spokesperson for the American Academy of Ophthalmology. We asked him this question. Here's what he said:

How much unfiltered sunlight should you receive? Take home message, aim for 10 to 15 minutes of direct, unfilter morning light. No windows, no sunglasses, as soon as practical after waking up. In fact, the best and safest time to do it is in the first 45 minutes after the sun rises. We need to have a circadian reset at the retinal level.

So, why early morning? Well, turns out there's a pretty fascinating reason for this...

Early in the morning, the sun is coming at a pretty acute angle on the atmosphere. A lot of the bad stuff, the UVB light, the really short wavelength light that's bad for us jumps off the atmosphere, so we don't get that. Our skin doesn't get it, and therefore it doesn't red, even if you're outside 10, 15 minutes, that's a clear sign that it's still safe. And your sunburn risk is almost zero at that early point in the mornings, and it allows your vitamin D production to happen.

So again, just to reset morning light in particular, Deirdre, that's what you got to pay attention to. Helps reset your circadian rhythm, boost mood, improve sleep, give you a skin safe dose of sunshine so that your body can make vitamin D. And get this, Dr. Maturi says it's even more than that. Having that sort of sunlight can actually play a role in preventing nearsightedness, especially in kids.

'When you have bright outdoor light like 10,000 plus lux, which happens first thing in the morning, it triggers dopamine release in the inner retina. And this dopamine is the principal stop signal that keeps the eyeball from lengthening. And our eyeball is at most risk for lengthening in the first 20 years of life. And this is data that's been clearly shown published, 20 to 50% lower incidence of myopia and slower progression when daily outdoor time is front-loaded in the beginning of the day.

But, now this is the important part: he says that as sun climbs higher in the sky, it is time to switch gears.

'It's really critical, especially if you're supremely light-skinned, if you have light-colored hazel eyes or blue eyes that you have some sun protection on for midday sun, definitely after 10 a.m. to 4 p.m., that's when 50% of our daily UV dose happens. So when the sun is so much stronger, you definitely want to have protection both on skin and on your eyes.

'That midday sun can do real damage over time. In the short term, it can cause sunburned eyes, something called photokeratitis. It can show up as redness, watery eyes, even blurry vision. That usually clears up within a day or two, but there are long-term risks that are more serious. One of the biggest, something known as macular degeneration. That's when the center part of your retina, called the macula, starts to break down. And that can lead to blurry vision or even permanent blind spots. And while it's more common as we age, too much sun exposure over the years can definitely raise your risk.

About a third of Caucasian populations have a higher risk for macular degeneration and many of them develop it. 30% of the population who's over 80 has significant macular degenerations and smaller percentages over 60 and 70 years of age. So all of that happens in many ways due to oxidative damage, from food, from high blood pressure, from being overweight and also being exposed to too much direct sunlight.

Dr. Maturi also said that there are some studies that show UV ray exposure can increase the risk of cataracts. So to sort of summarize here, Deirdre, aim for 10 to 15 minutes of early unfiltered sunlight every morning. Time frame is really important here. But after that, protect your eyes. Use polarized sunglasses, especially if you're around water or sand. And one last thing, since firework season is here, Dr. Maturi had a quick safety reminder.

July 4th is right upon us, and a small tip, wear safety glasses when you're with fireworks. As a retina specialist for the last 25 years, I have operated on July 5th, 6th, and 7th fixing eyes that are often irreparably broken. Launch injury is so big, so common, and fireworks are everywhere, everybody wants use them, especially kids. 90% of it is towards men, so the men out there be super careful. Please don't be that statistic. Save those pretty eyes because eyes are delicate. So have them protected.

Coming up, you know sunscreen is important, for sure, but how much should you be using? We get so many questions about that. And does that old bottle in your cabinet still work? We'll have that right after the break.

All right, Kyra, time for another question... Take it away.

Well, Sanjay, Deirdre's question kind of got me thinking. So now that we know a little bit of morning sun can actually be good for us, what about all that time after? I feel like sunscreen is a bit of a mystery at times. So what kind should we be using? You know, what SPF level? Or how much is actually enough to protect us?

Okay Kyra, this is a great question because all the options really can sometimes be confusing. On a past episode of Chasing Life, we went straight to the experts to sort these things out and importantly to find out what these experts actually do themselves. I find that you can get great insights by asking people how they incorporate their own knowledge into their daily lives. So first up, epidemiologist Dr. Rachel Neale to help explain the two types of sunscreen, mineral also called physical sunscreen and chemical.

The physical blockers, so the titanium and zinc sunscreens, they sit on top of the skin, basically, and form a barrier, whereas the chemical sunscreens, they sort of bind to the top surface of the skincare and turn the UV radiation into heat and then disperse it from the body as heat. I think it's very tricky, because the properties of the chemical sunscreens make them much more pleasant to use. The physical blockers tend to be a bit thicker a bit of a white veil on the skin. So from a just a usability perspective, I use a chemical sunscreen every day.

So think of physical sunscreen as forming a literal physical shield on your skin, while chemical sunscreens absorb and then deflect UV rays. Now, whichever type you pick, it comes down to what works for your skin and your routine. So what should that routine be?

We actually formally recommend that people should apply sunscreen routinely on all days when the UV index is forecast to get to three or more. So we're advising people to just make it as routine as brushing their teeth. But on those days when their UV index is not gonna get to above three, we're suggesting that sunscreen is not needed.

Ok, that helps. What about other qualities? First, choose a broad spectrum sunscreen to make sure you have protection from UVA and UVB rays. Hopefully, you know that. As for SPF, well Dr. Neale says 30 plus is the minimum recommendation. Some people might prefer 50 plus for added coverage. But this is the key. It's not just about SPF. It's about how much you're actually using and how often you're applying it. And that's where Dr. Laura Vandenberg, a public health scientist at the University of Massachusetts Amherst, has some thoughts.

Based on what I know and in my own practice, lean towards a physical sunscreen. And then use correctly, right? More than you think you need and reapplying every 90 minutes. Most of us put on the amount of sunscreen that we feel is sort of enough so I can't see it, right. You know, you rub it into your skin, but that's not actually the way that they're intended to be used to protect us. So a colleague of mine would say, three full fingers of sunscreen just for your face. So we're not putting on enough, and really we should be putting on that amount on your face every 90 minutes if you're outside.

She also says how slowly you go through your sunscreen might be an indicator that you're not using enough.

In a couple days, you should use up the bottle. So if you have sunscreen that's expiring under your sink at home, number one, throw it out. But number two, you weren't using enough when you were using that product.

'One last tip, don't store sunscreen in hot places like your car, why? Heat can actually break down the active ingredients making that sunscreen less effective. So let me try and summarize this. Think of this as your sunscreen checklist. Number one, choose a broad spectrum sunscreen that works for you, can be physical or chemical. Number two, use enough, remember three fingers worth just for your face. Number three. Re-apply every 90 minutes when you're outdoors. Number four, make it a daily habit whenever the UV index is three or higher. You can check that. Number five, store your sunscreen somewhere cool. And finally, don't forget the other basics, hats, shade, sun protective clothing. They all go a long way. That's it for Paging Dr. Gupta today. Wishing you all a safe and sunny summer. Thanks to everyone who sent in questions. I really appreciate that. We are building this show together. You're a big part of it. If there's something health related you've been curious about, don't be shy. Share it, record a voice memo, email it to asksanjay@cnn.com, or give us a call, 470-396-0832. Leave a message. Thanks for listening. And I'll be back next Tuesday.

Chasing Life is a production of CNN Audio. Our podcast is produced by Eryn Mathewson, Jennifer Lai, Grace Walker, Lori Galaretta, Jesse Remedios, Sofia Sanchez, Kyra Dahring, and Madeleine Thompson. Andrea Kane is our medical writer, our senior producer is Dan Bloom, Amanda Sealy is our showrunner, Dan Dzula is our technical director, and the executive producer of CNN Audio is Steve Lickteig. With support from Jamus Andrest, Jon Dianora, Haley Thomas, Alex Manasseri, Robert Mathers, Leni Steinhardt, Nichole Pesaru, and Lisa Namerow. Special thanks to Ben Tinker and Nadia Kounang of CNN Health and Wendy Brundige.