Board Thread:Theories and Speculation/@comment-25132842-20180320052324/@comment-6769189-20180320211332

I always figured Indra was a special case since he was the direct and most immediate descendant of Hagoromo's that his MS didn't make him go blind.

Perhaps the cells from Asura's bloodline provide the healing factor necessary to stop the degradation, as with Obito. Obtaining 6 Paths chakra/power strengthen the body so the eyes withstand/lessen the strain.

As for why MS+MS stops the degradation, i havent the slightest idea why that could be. Maybe mixing the 2 chakras from both eyes strengthen the eye or something.