Originally Posted By Bill Kennedy
It seems like the "space blanket" or maybe black 2mil polyethylene might work but possibly cause condensation or ventilation problems. Sleep masks may be another idea worth considering:

https://www.dreamessentials.com/articles-faq-025-what-as-an-eye-shades

That sounds like a good idea and draped over the rainfly should not introduce condensation, although I understand Iceland can be relentlessly windy and between fly and tent may be needed to keep it from flapping and blowing away.

Otherwise, sleep masks or cinching the sleeping bags really tight.
_________________________
--Rick