In all the events of Skyrim, the Dragonborn read a total of THREE scrolls, one of which that was improperly. According to Dexion Evicus, Moth Priests go blind in their later days after reading a scroll, and varies by their preparation before reading. This means to any ordinary mortal who reads a scroll at all, they can go blind within a matter of days. I'm thinking that the Moth Ritual only extends the amount of time before blindness by months, or years probably
The Dragonborn read one of the elder scrolls at the Throat of the World, improperly. Should've the Dragonborn go blind after a couple days? Probably. But since that didn't happen, we can assume that the Dragonborn completed the Dawnguard questline before learning Dragonrend, since during that questline, dialogue with NPCs suggest the Dragonborn had no idea how to read a scroll. Therefore, with knowledge of the scrolls in Dawnguard, the Dragonborn would have more experience with reading the scroll to learn Dragonrend, before "Alduin's Bane". Thus, the time before blindness is extended.
And with that, do you think the Dragonborn could be canonically blind by TES 6?