I mean as far as we know when Madara and Izuna had their mangekyou sharingan there was no medic ninja in that era, there was no medic ninja uchiha as far as I know.
When Sasuke and Itachi got their mangekyou sharingan there was no medic ninja to try and heal their eyes.
Since Sarada is in Konoho and there are many medic ninjas, when Sarada unlocks the mangekyou sharingan surely there be medic ninja able to prevent blindness. The one solution is Hashirama DNA, that prevented Obito going blind after all the years using Kamui.
When Sasuke and Itachi got their mangekyou sharingan there was no medic ninja to try and heal their eyes.
Since Sarada is in Konoho and there are many medic ninjas, when Sarada unlocks the mangekyou sharingan surely there be medic ninja able to prevent blindness. The one solution is Hashirama DNA, that prevented Obito going blind after all the years using Kamui.