Could you elaborate on the bio/mechanics/physics/chemistry of this? If light can still pass through a frozen retina, what would cause the total loss of vision? Is it because of total neural inactivity?
It’s not that the light needs to pass through the retina per se - the retina contains the layer of cones and rods in the back of the eye that receives light and translates it into signals, feeding it to the optic nerve and thus into the brain. Freezing the retina would kill those cells, destroying our “optical input.”
Debate is pointless - we need some hard data. Someone needs to take one for the team. Unfortunately, it’s in the 50’s outside here so I can’t volunteer.
Okay, then I’ll start with a wimpy bid of -23° F (-30.6° C) outside with no wind. Eyeballs were fine even after 10 minutes; (Location 10 miles north of Nord, Kalaallit Nunaat on the pack ice). Surely, other Dopers have endured much lower temps, right? 
Imagine the chaos if we sent you on this mission.
Search Team Member 1: EdwardLost! EdwardLost!
Search Team Member 2: What?? We lost him? Nooooooo!!!
Search Team Member 1: No no, we didn’t lose him. We’re just looking for him
Search Team Member 2: Look! A shiny frozen eyeball! Whose is this?
Search Team Member 1: Maybe it’s the one EdwardLost lost
Search Team Member 2: Dude, your voice is echoing
32° Fahrenheit. If you’re already dead at the time.
ETA: Hmm, maybe a bit lower than that. Salinity.
I would imagine rods and cones would stop functioning long before they reached 0C, as wiki says cell metabolism slows at 30C.
Yeah, good point. I was more noting that the retina doesn’t merely allow light to go through it, though in a sense that is a description of what it does - rather than passively allowing light through, it actively “passes” light through to the brain, by encoding it into nerve impulses.
Probably the biggest concern would be the aqueous and vitreous humors freezing, rather than the retina freezing. The aqueous humor (between the lens and the cornea) is mostly water, so were it to freeze, it would expand and damage the cornea, as well as likely displacing the lens. So at best, at that point, you might be able to tell light / dark, but would not see any images.
The vitreous humor, within the eyeball, is more gelatiny, so would require lower temps to freeze. If it were to expand, then you’d basically be looking (heh) at a ruptured eyeball, so no more seeing anything at that point.
I have gone for runs outside when it was -50 (with the windchill, are we including that?).
My eyeballs are fine and unfrozen.
We also have people deployed to Alert, NU, send re-supply trips regularly and have not received any report of frozen eyeballs - or of people getting hypothermia from freezing the cold air.
I think that your eyeballs and lungs can freeze - but the rest of you gives out first and you die.
A good link to this question, eyelighting the heat of the vitreous humour, is http://cardhouse.com/berk/science96.htm.
It also deals with how to pee your name in the air and have it turned into peesicles before hitting the ground.
Great link! It reads almost as though Cecil wrote that.
A news story in Ottawa, Canada, today claimed that a woman skating on the canal yesterday got frozen eyeballs. I’m going to guess they didn’t totally freeze, but only the external layer. It was -25 Celcius and the windchill was -39 Celsius at 9 AM. (for comparson -40 Celsius is -40 Fahrenheit, the scales intersect at that point).
also from the reporter:
I do know that I heard my cousin the professional mountain climber say things like “the next time my eyes started freezing…”
The first time he attempted Everest, it was a clear, sunny day and, being the youngest team-member, he was opening the way; he had taken his goggles off and at one point complained about the mist which had been growing. “What mist? 
” was the answer from his cord-mates - at which point he got a scolding on the lines of “see, we’d told you not to take the goggles off… and that is exactly why!” and got sent back down to camp. It happened again to him at least twice more (both times with goggles on), but never so badly because he was able to recognize the symptoms and turn tail before things got that far.
I have no idea what kind of temperatures that was, but it apparently is common enough. It doesn’t cause permanent damage: mountain climbers lose fingers and toes to frostbite with depressing frequency, but eyeballs recover fine once they warm back up.
(And no, I can’t ask him, he’s a bit dead. Hypothermia in the Himalayas; Iñaki RIP)
I immediately thought of the story “Wait It Out” by Larry Niven.
EDIT: And shortly thereafter, “Inferno” by Larry Niven and Jerry Pournelle.
I just did the math. Short answer? Not true.
Longer answer:
Assume absolutely dry air is inhaled at ambient temp, and that air is then exhaled at body temperature (37C) and 100% relative humidity. Heat is lost from the body due to the warming and humidification of that air.
Assume typical parameters for an adult male at rest: 16 breaths per minute, 1/2-liter tidal volume.
Assume ambient temp of -60C. I calculated heat loss via respiration to be 29 watts. For reference, heat loss (via respiration) when ambient temp is 0C is 19.2 watts, so the heat loss at -60 is only an additional ten watts on top of that. (humidification requires an impressive 13.2 watts, no matter the ambient temperature; this is why the total power requirement doesn’t drop that rapidly with increasing ambient temp.)
Various web references indicate that a normal human bean at rest produces 60-90 watts of heat. If your body is perfectly insulated, you’ll eventually overheat since you’ll only be dumping 29 watts through respiration.
I couldn’t replicate your calcs. My calcs show substantially higher wattage. Can you please check your calcs ? Here are my calcs
Actually the situation would be better than that because our sinuses contain structures called conchae (or turbinates) that serve as heat exchangers. We breath in cold dry air, it’s warmed and moistened before reaching the lungs. We breath out warm moist air, it redeposits heat and moisture on the conchae and what’s exhaled is cooler and drier than it would have been. If in cold weather we use a mask or scarf we’re artificially extending the heat exchange.
8 liters per minute, .001225 grams per liter, so flow rate is 0.0001633 kg/s.
Temp increase is 37-(-60) = 97C (or 97K).
Constant-pressure specific heat of air is 1006 J/(kg*k).
So heat loss rate due to warming of the air you exhale is
0.0001633 *97 * 1006 = 15.94 watts.
At 37C, the moisture content of saturated (100% RH) air is 0.0411 kg of water per kg of dry air. So assuming you have inhaled bone-dry air, your water loss rate is
0.0001633 * 0.0411 = 0.00000671163 kg/s.
The heat of vaporization for water is 2260 kJ/kg. So the heat loss rate due to humidifying the air you exhale is
0.00000671163 * 2260,000 = 15.17 watts.
My grand total is 31 watts. A bit higher than the 29 watts I had ten years ago. Chalk it up to inflation? Not sure where I got my values for the various constants back then, but I’m close, so I think I did the math the same.
Did I screw up somewhere?
@Machine_Elf - I uploaded the calcs as a picture in my post. Can you please click that ? It has the details you provided. trying again : Pasteboard - Uploaded Image