Vision & Blackout

[Milt]

Loss of Vision Under High g?

What is it that causes our eyes to 'black out' almost immediately upon the application of about 5g or more when sitting upright to the force?

As a former fighter pilot and TP I have never learned of a satisfactory explanation. Maybe there is one out there somewhere amongst the avmed fraternity.

Does the optic nerve need at least an uninteruptable minimum level of blood oxygen or is it brain related or both?

Perhaps a mini g collar around one's neck to stop reverse blood flow through the carotid arteries for a short period would retain vision and consciousness during very high g manoeuvres.

[Loose rivets]

What a brilliant idea.

Signed, The Enemy.




There was a diminutive 1st Dan in our club who got his black belt with both the AJA and BJA, in contest, using that technique.


Seriously though - Perhaps one of the best layman's descriptions of brain wiring - using the vast visual system as his example - was by Francis Crick, in his Astonishing Hypothesis. Mind you, even that time ago, scientists didn't know quite what the crossover point on the optic nerve did.

Shared data for both sides makes the whole system very vulnerable to a uniform shut-down of processing. The vascular support of the blood's weight is designed to be balanced at 1g. Alter the load on the fluid, and it's easy to see why it's not . . . erm, easy to see.

[gingernut]

do the visual disturbance happen with positive or negative g?

From memory, (flying an A10) it's negative g? (but that was ony a video game)

[Milt]

gingernut

Excessive ? negative g causes our eyes to suffer 'redout' Somehow the eyes must become gorged with blood which we try to see through. Too much overpressure then results in rupturing of the fine blood vessels of the eyeballs. Perhaps there is then a risk of permanent damage.

Does anyone know the amount of negative g required to cause noticeable redout?

[Loose rivets]

I often find myself going back to Col. Stapp.


43 g and one of 46.6 g. "his eyes were engorged with blood."


Loads of stuff on him.

Col John Stapp Takes a Lot of G's - YouTube

[gingernut]

Wonder if it's related to this sort of thing... ? [Ocular alterations associated wit... [Arq Bras Oftalmol. 2005 Nov-Dec] - PubMed - NCBI (http://www.ncbi.nlm.nih.gov/pubmed/17344993)