Board Thread:Theories and Speculation/@comment-27916438-20170329044844/@comment-734582-20170411144150

Ravenlot 27 wrote: Doesn't necessary have to be so. If it's Hashi's DNA that prevented Obito from going blind, then it's seemingly because of the enhanced regeneration that healed the eye True, but the point is that the eye losing it's light isn't a feature, it's actual damage being done to the eye, that can be healed even by external means. This isn't present in ANY other eye, not even the Rinnegan or Rinne Sharingan. So i think it's clear that the Mangekyou isn't meant to lose it's light, it's simply that the Uchiha's KKG has deteriorated too much.

DMS Kakashi suffered no side-effects even though Kakashi's sharingan already lost most of it's light, so clearly more powerful chakra takes away these dojutsu problems.