Board Thread:Theories and Speculation/@comment-28323245-20170530200422/@comment-734582-20170531205349

Lorenzo.r.1st wrote: well, we never are actually told why the ms go blind, for one, so there probably isn't any known ways to even counter said effects But there is, since Obito spammed his MS powers like crazy yet showed no signs of degeneration. So clearly, the MS doesn't have to go blind.

The most notable difference is that Obito has zetsu cells. So if the MS loses eyesight due to actual, physical damage, then Hashirama's cells could repair that.

Similar or even superior eyes like the Rinnegan or Rinne Sharingan suffer no such effects. However, the Rinnegan appears to be a physical eye, so maybe it's the fact that the MS is really just a manifested power that creates such damage (That is, the normal human eye isn't strong enough to hold such power).