It wasn't the macadamias. I eat those too and no IR vision. Please find out what it is, it's a very cool ability that I'd like to have too. :-D

Maybe it was the full moon - as it was full last night, but then, why doesn't everyone have it?

It's a hard thing to google since it comes up with lots of stuff about infrared light and FLIR and cameras. But I did find this one interesting thing that mentions a form of vitamin A called A2: http://www.edkeyes.org/blog/050825.html

I did some quick checking on this, and though I couldn't find any references to military research, there were some examples in the regular civilian literature. Yoshikami, Pearlman, and Crescitelli (Vision Research 9:633-646 1969) did a similar experiment on rats, putting them on a diet which was deficient in vitamin A and supplementing it with additions of either vitamin A1 (the normal form) or A2 (the altered one). No behavioral studies were done, but they did extract the retinas and perform some spectral analysis, with the result that there was indeed some alteration of the photopigments, specifically the addition of a second form with sensitivity shifted redward by about 20nm.

That study cited Millard and McCann (Journal of Applied Physiology 1:807-810 1949) which was an experiment on humans, albeit with fairly loose controls on diet. They found that behaviorally the group taking A2 supplements had slightly improved red sensitivity, but didn't provide any detailed spectral response curves.

There's a link in the above site to this one: http://vm.uconn.edu/~lundquis/links.html#sensation which has more details:

Infrared vision: Here is a description of a military experiment attempting to give humans "infrared vision", or the ability to see in the dark based on radiation we normally only experience as heat (since it's outside the range of our eyes' light senstivity). This is a third-hand account but I've included the citation of the second-hand account in case anyone can track it down...

from Sekuler, R., and Blake, R. (1994). Perception (3rd ed.). Springfield, Ill.: Thomas. pp. 62-63: The following story dramatizes how photopigments determine what one can see. During World War II, the United States Navy wanted its sailors to be able to see infrared signal lights that would be invisible to the enemy. Normally, it is impossible to see infrared radiation because, as pointed out earlier, the wavelengths are too long for human photopigments. In order for humans to see infrared, the spectral sensitivity of some human photopigment would have to be changed. Vision scientists knew that retinal, the derivative of vitamin A, was part of every photopigment molecule and that various forms of vitamin A existed. If the retina could be encouraged to use some alternative form of vitamin A in its manufacture of photopigments, the spectral sensitivity of those photopigments would be abnormal, perhaps extending into infrared radiation. Human volunteers were fed diets rich in an alternative form of vitamin A but deficient in the usual form. Over several months, the volunteers' vision changed, giving them greater sensitivity to light of longer wavelengths. Though the experiment seemed to be working, it was aborted. The development of the "snooperscope," an electronic device for seeing infrared radiation, made continuation of the experiment unnecessary (Rubin and Walls, 1969). Still, the experiment demonstrates that photopigments select what one can see; changing those photopigments would change one's vision. p. 546: Rubin, M. L., and Walls, G. L. (1969). Fundamentals of visual science. Springfield, Ill.: Thomas.

So maybe something you ate was high in whatever this vitamin A2 is? If you find out, pls let us know. :)

I did find this on Vitamin A2 (pdf link).

3,4-Didehydroretinol (vitamin A2, DR, dehydroretinol), a naturally occurring analogue of retino) (vi tamin A,, R), is active in vision, growth and cellular differ entiation but is converted to retino! in very small amounts, if at all.

But no mention of infrared. Apparently, it's found in fresh water fish:

dehydroretinol vitamin A2, the form, C20H28O, of vitamin A found in the retina and liver of freshwater fishes and certain invertebrates and amphibians; it differs from retinol (vitamin A1) in having one more conjugated double bond and has approximately one-third the biological activity of retinol. Called also retinol2.

So, have you been eating fish livers or eyes recently?