I was able to find two case studies showing direct links from vitamin A levels (and liver damage) to night blindness. I’ve edited my initial comment with the links to them.
Comment on Intelligent Design
dragonfucker@lemmy.nz 3 weeks agoSource that retinal concentration is related to dark adaptation?
AnarchoEngineer@lemmy.dbzer0.com 3 weeks ago
Whats_your_reasoning@lemmy.world 3 weeks ago
I’m not OP and I’m not an expert, but I know that the production of rhodopsin requires retinal. Rhodopsin is a light-sensitive protein our eyes use to see in low-light conditions, and is essential for our night vision. Retinal and retinol are not the same thing, but they both come from Vitamin A, and convert into each other during the visual cycle. Which means that a deficiency in Vitamin A = a deficiency in retinol, retinal, and rhodopsin, which in effect leads to night blindness.
But I’d like to know more/get a source for OP’s liver connection. I know most of our retinol is stored in the liver. However, I’m having difficulty verifying their claim that the delay in night vision onset is due to it traveling from the liver to the eyes. From what I can find, the retinol ligand that produces rhodopsin already exists in mammalian eyes (and persists there as part of the aforementioned visual cycle.) So the argument that night vision takes so long because retinol needs to transfer from the liver to the eyes is suspect.
Unfortunately, search engines absolutely suck these days, and almost every article I can find is behind a fucking paywall. So I’m struggling to find information that can either confirm or deny OP’s claim.
OP, please provide a source! Inquiring minds want to know more!
AnarchoEngineer@lemmy.dbzer0.com 3 weeks ago
Honestly, it was pretty hard for me to find a source which has made me a little skeptical of my own statements.
I was able to find two case studies in which patients with liver damage that caused them to have low levels of vitamin A exhibited night blindness. Both were treated for vitamin A deficiency and saw symptoms improve.
The strongest evidence of my original claim is the fact that one of the patients had otherwise healthy eyes and vision, only having extreme trouble seeing at night. After receiving treatment for vitamin A deficiency, her night vision improved. This suggests that dark adaptation is dependent on vitamin A in the blood which is regulated by the liver.
However, I’m now somewhat skeptical and curious myself considering these two studies were almost all I could find on this topic. If I have more time I’ll try digging deeper. For now though, I’ve edited my comment with links to the studies.