According to Karl-Arne Stokkan, Professor of Arctic Biology at Tromsø University, his new study, published on Wednesday in the Proceedings of the Royal Society, is the first scientific coverage of the phenomenon.
"This has never been discovered because no one has studied the animals experiencing extreme lighting conditions throughout the year," he told VG newspaper.
The study was done in conjunction with the Institute of Ophthalmology at University College London and Moorfield's Eye Hospital in London.
The authors believe that the change may make the animals' eyes more sensitive to light.
When they tested the retinas of live anaesthetised animals, they found that the blue winter eyes were at least a thousand times more sensitive to light that the golden summer ones.
"The blue reflection in winter is associated with significantly increased retinal sensitivity compared with summer animals," the authors concludes in an abstract of the report posted on the Royal Society's website.
The authors point out that although the change worsens reindeer's eyesight, it nonetheless may help in Arctic winter conditions.
"Increased sensitivity occurs at the cost of reduced acuity, but may be an important adaptation in reindeer to detect moving predators in the dark Arctic winter," they conclude in the paper.
The paper claims that this the first time such a phenomenon has ever been recorded.
"This is, to our knowledge, the first description of a retinal structural adaptation to seasonal changes in environmental light."
Here's a video on the research put together by the Biotechnology & Biological Sciences Research Council: