Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
14 Jul

Dear Mark: Sun Exposure and Eyesight; Vasectomies

EyeFor today’s edition of Dear Mark, we’ve got a quick two-parter. First, I discuss the pros and cons of ocular sunlight exposure in children (and adults). Should kids leave the house with a pair of wraparound goggles every single time, or are their prepubescent eyes safe without them? If too much sun exposure is bad, is none the best? Then, we cover the pros and cons of getting a vasectomy. Are there real health risks, like increased chances of cancer and/or heart disease? Will you lose functionality down there and experience a drop in testosterone?

Let’s go:

Dear Mark,

The linked WSJ article seems a tad overblown with respect to the risks the sun poses to kids eyes. Would love to get your take.

It’s very similar to the conventional wisdom on sun exposure for skin: less is better, all the way to zero. In my view, that simply can’t be optimal for humans.

I’ve got three girls. Should I be sending out into the world with sunglasses, always??


It depends.

While I’m definitely a fan of the sun and regular sun exposure, and I agree that the article is pretty alarmist, there are real issues with too much sun exposure to the eye:

Photokeratitis – Temporary inflammation of the cornea from excessive UV radiation. This is basically a corneal sunburn. Painful but reversible and doesn’t seem to cause any long term complications. Snow-farers know it as snow blindness because the highly reflective snow amplifies the UV. The Inuit even made snow goggles from caribou antlers, cutting slits that allowed just enough light to see without causing snow blindness.

Pterygium – Mostly cosmetic, a pterygium is a blemish along the conjunctiva (the thin layer lining the white of the eye) that can become irritated and inflamed. Evidence shows that UV exposure is a likely risk factor, with outdoor postal workers experiencing higher rates of the condition.

Cataract – The leading cause of blindness, cataracts form when proteins in the lens unravel, become entangled, and absorb pigment that then increasingly obscures the vision. Ocular UVB exposure is a risk factor for cataract formation, which is why French mountain guides – who are constantly outside during the day without much respite – have far more cataract formation and surgery than non-guides.

Overall I’m with you, James. Sunlight is a reality of the outside world and unavoidable if you’re outside; we are creatures of the outdoors. We’ve established that moderate amounts of sunlight are definitely good for our skin and our overall health, and it’s difficult to fathom that going outside for an hour or two without judiciously slapping a pair of Blue Blockers on immediately would place our eyesight in mortal danger. Too much? Sure, that’s true for most stimuli, let alone the light from a massive ball of cosmic energy illuminating. But a normal, sane amount? Given the ubiquity of sunlight in the natural environment and the fact that we’ve evolved in said environment, it seems implausible that any modicum of sunlight is dealing major damage to our eyes.

There may also be benefits to unfiltered ocular sun exposure. We often talk about the dangers of excessive light at night disrupting your sleep by inhibiting melatonin secretion. Well, the opposite happens when you get it during the day: it wakes you up and establishes (or maintains) a healthy, natural circadian rhythm. If you’re always avoiding full spectrum, truly bright daytime light, your rhythm will be off. And sure enough, people who get the most light during the morning and daytime begin producing melatonin earlier in the evening. There’s nothing better than full on sunlight to provide that.

Is there a time for sunglasses? Yes, just as a good UVA-and-UVB-blocking zinc oxide sunscreen can come in handy when you know you’re going to be out in the sun without shade for longer than you and your skin would prefer, a pair of sunglasses that block both UVA and UVB can help protect your eyes in the same situation. Doubly so if you’re in the snow, on a body of water, or at the beach where the power of UV is reflected and magnified; glasses are a good option to have in these situations. I wear ’em myself – just not all the time.

I would provide sunglasses for your girls, not force them. As the pediatric opthomologist in the article even mentions, it’s better to run around and play outside without sunglasses than sit inside and watch TV. Besides, your kids are probably eating nutrient-dense, antioxidant-rich food, and that’s protective of the eye against sunlight damage. A smart, sane position is to get some sunlight directly in your eyes each day. Not a huge amount. Don’t stare into the sun on purpose or anything silly like that. Just go outside without sunglasses on (but handy in case you need them), go about your business, and the light will come to you.


My wife and I are done having kids, but we’re also done with condoms and birth control. Neither of us can stand either, so I’m thinking hard about getting a vasectomy. Is there anything I should know? Are there any dangers associated with the procedure and the aftermath? I want everything else to work as intended, ya know?



Good news, Tim. The evidence strongly suggests that your facilities will remain fully operational, your sex life will improve (or at least stay the same), and your testosterone levels will be unaffected. All they’re doing is capping the vas deferens – the tubes that deliver sperm during ejaculation. You can still ejaculate, and the “body” is none the wiser. You’re just “inactive.”

  • In one 2005 study of 64 men about to undergo vasectomy surgery, researchers analyzed their sexual function pre-op and 90 days post-op. 67% of the men improved their function after surgery, while 17% worsened and 16% remained constant. Another study found that roughly a third of men enjoyed improved sexual function after vasectomy, while nearly 50% remained unchanged. The results differ across other studies, but for the most part the vast majority of men enjoy improved or unchanged sexual function after getting a vasectomy. If you’re happy with your work now, you’ll be fine.
  • Vasectomy seems to increase sexual satisfaction among couples as well. Husbands who received vasectomies and wives who received husbands who received vasectomies both reported improved sex, with the women enjoying the biggest increases in satisfaction. 93% of the males and 97% of the females would “recommend and do vasectomy again,” such were the benefits.
  • Rats who get the snip have similar testosterone profiles as intact rats. Although no human data exists, the fact that erection function and sexual satisfaction usually either increase or stay the same in post-op men indicates that testosterone is unaffected.

Associations between vasectomies and various health risks have been proposed, however.

Heart disease: There were very faint inklings of a connection between the two, but recent evidence has ruled it out.

Cancer: Much the same story as heart disease. Suspicion has made way for exoneration. Testicular cancer? No connection.

You might have seen the reports of a new study showing a link with prostate cancer. That’s true, and the headlines are scary. But consider that men who’ve had a vasectomy are probably more frequent visitors to the urologist than intact men. They’ll be receiving more tests in general and there will be more opportunities to take prostate cancer tests. Even still, the increase in absolute risk potentially caused by vasectomy remains low.

Sex with a loved partner is very important for many people. And on a physiological level, it’s extremely healthy. If this vasectomy will help you have more and better and less stress-free sex with your wife, it’s absolutely worth the very slight potential increase in prostate cancer risk. Go for it.

Thanks for reading, all. Let’s hear what you have to say about all this in the comments!

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. I had my vasectomy a few decades ago. I didn’t want to add to the mass of humanity. It worked a treat. No kids; cheaper than a school uniform. Thank you Mr Mark.

    kem wrote on July 15th, 2014
  2. Oh, I had snow blindness at about 15 years… didn’t know it could happen; hadn’t ever had a pair of sunglasses. Man did that hurt. I couldn’t decide whether it hurt more to have my eyes open or shut.

    After three thirty five years of alpine guiding, I know when to wear them. I love to use my amber goggles skiing in bad light. Amber lenses are pretty good (mtn bike) riding in the forest. I hear they are pretty good for getting to sleep, as well.

    kem wrote on July 15th, 2014
  3. The sexual performance boost comes from carefree f–king and perhaps even sperm retention, both completely achievable without the vasectomy. I think the only benefit is having sex whenever you want without a condom, with no worries of pregnancy.

    But just in case anyone doesn’t just want to hear how great a vasectomy is, and know of potential problems, here’s a quote from Chris Kresser on how a a vasectomy can lead to potential problems:

    “That’s a great question actually, and I did a little bit of research on this and I guess what we can say is the jury’s not out, but there is enough research to give me pause, if that was something I’m considering, which I’m not obviously. First of all let’s step back a little bit, I mean the idea that the vasectomy is totally safe is not quite accurate. As any man will testify the testicles are very delicate and sensitive structures. They’re complex organs with a really rich nerve and blood and lymph supply, and they’re under this intricate hormonal control that we’ve already talked about during the show. And also intricate temperature control that regulates sperm and testosterone because sperm has to be produced in a pretty narrow temperature range. And another thing is that the sperm is really tightly isolated from the rest of the body so that the man doesn’t produce antibodies to his own sperm, which as far as the rest of the body is concerned sperm is a foreign protein. So there are these defenses that keep the sperm isolated from the immune system. Now all of that, that intricate hormonal and temperature control, the defenses that keep sperm isolated, the delicate physiological structures can be disrupted even when the vasectomy seems to have gone well. And there can be short and long term complications which can be serious. So there’s a clinic, the Harley Street Clinic which is a place where they specialize in treating andropause and some of their own internal research, this isn’t double blind placebo controlled stuff it’s anecdotal but in their experience over the past ten years 25% of men who have come in for treatment for andropause have had a vasectomy. And that’s about twice the level in the general population. And in some of the surveys they’ve done, 35% of men who have filled out this andropause checklist and had andropause have reported a vasectomy in the past and some sister impotence clinics in Australia that they work with have reported a rate as high as 45%. So we don’t know for sure what the mechanism is there but one of the theories is autoimmunity related to sperm released into the tissues after the vasectomy. In other words that defensive structure that keeps the sperm away from the immune system is disrupted and then the immune system becomes aware of the sperm and treats it like a foreign protein, starts producing antibodies to it and then that becomes sort of an immunological time bomb. So to summarize, we don’t know for absolute sure that a vasectomy can increase the risk of andropause but there certainly is some evidence suggesting that it does and there are some clinical studies above and beyond the anecdotal studies that I mentioned that have shown increase in anti-sperm antibodies shortly after a vasectomy in animal studies and there’s been a couple studies that have shown an increase in LH levels after a vasectomy which could indicate a compromised ability to produce testosterone. And then there’s been some other studies about general increase in autoimmunity after that surgery. Anytime you have a surgery like that there’s a risk, and so I think it’s real, but what the likelihood of something happening is not entirely clear.”

    MC wrote on July 15th, 2014
  4. “with the women enjoying the biggest increases in satisfaction. 93% of the males and 97% of the females would “recommend and do vasectomy again,” such were the benefits.”

    No suprise there… it’s not about the pleasure of having sex for the woman…it’s the relief at not having to nag her husband ever again!

    Ha ha

    Peter wrote on July 15th, 2014
  5. Sun exposure is all about moderation. If you’re healthy, your body will make it obvious when you’ve had enough. No sun at all is bad news. Protection is a good thing once we’ve had our dose!

    Good to know about the vasectomies! Some day…haha.

    Graham Ballachey wrote on July 15th, 2014
  6. From what I have seen regarding eye sight (sorry I love puns!):

    Sunglasses should be used about as often as sunscreen – never if you can help it.

    Just as sunscreen blocks the BENEFITS of exposure to the full spectrum of sunlight (UV Rays), including the synthesis of vitamin D, sunglasses block the benefits to the eyes. Which are quite substantial. Among other things, lack of UV exposure (via sunlight @ safe hours) in children shows a vastly increased risk of developing eye troubles like myiopia/near sightedness.

    An affinity for shade, a wide-brimmed hat, protective clothing such as loose fitting, long sleeve shirt etc. is the way to go. Unless you plan to go out on the boat or snowboarding – where the reflected sunlight reflects off the surface of the snow/water – most people should NOT be wearing sunglasses.

    Derek wrote on July 15th, 2014
  7. Regarding the vasectomy, my personal experience is that my desire/function remained the same or actually increased (probably due to not worrying about more children…5 is enough!) but the intensity of my orgasms decreased dramatically. I did not think to research this side-effect prior, and it probably would not have altered my decision, but it is somethign to be aware of.

    Steven Warren wrote on July 15th, 2014
  8. I had to have an ablation in 2006 so my husband had a vasectomy to make sure a pregnancy ever happened. I was 43 and we had no kids and I didn’t want any. A year later I wanted a baby so we adopted one.

    He did have some problems with the vasectomy because he didn’t ice it properly and developed a major hematoma. The really young ER doc came into the room and said “Dude, quit letting the boys swing in the breeze and go get a jock strap.” Funniest thing I’ve ever heard in the ER.

    hockeyfan7 wrote on July 15th, 2014
  9. One point that needs to be considered with regards to sunglasses and sun exposure for your eyes – the balance of UVA and UVB they are getting.

    It’s no surprise that Postmen would get eye problems…they spend all day driving around in mail trucks and are primarily being exposed to sunlight THROUGH GLASS, which filters out UVB rays but allows UVA rays through.

    Then you have the snow and water folks who are exposed to long hours of UVA rays reflecting off the land/water scape.

    Remember that UVA and UVB exposure works in synergy for the human body to benefit from natural exposure. But conditions such as long term exposure to sunlight through glass (automobile and/or clear building glass) or in an environment where UVA rays are reflecting constantly are where you definitely should be wearing sunglasses, while going to the park or in your backyard at mid day should be the perfect opportunity to not use sunglasses and let your eyes get naturally beneficial sun exposure.

    Keoni Galt wrote on July 16th, 2014

    Still want a vasectomy?

    Trevor wrote on April 9th, 2015
  11. Rates of vasectomy are low among doctors, and extra-low among urologists — the specialists who have to repair the damage. Like vaccination, there are no long-term, double-blind studies for testosterone levels, especially more than 5 years post-op. Male health clinics treating low-testosterone syndrome report disproportionately-high numbers of patients who have had vasectomies. Bottom line: they may appear to go smoothly at first but hypogonadism and chronic pain await some unfortunates. The medical mafia does not like keeping statistics on its failures.

    Trevor wrote on January 10th, 2016

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