I was just re-reading the news articles....

Robert Callow lost his sight on a similar accident, document in the news Wednesday 28 March 1877 - this was then further discussed in court/tribunal - 12 May 1877

Miles is mentioned as having been injured by an explosion of dymanite in the Laxey Mines a few months prior to the fireworks display - which was Wednesday 14 January 1880

Miles would have therefore been injured in late 1879 - however I can't find any newspaper articles that mention this explosion.

Therefore, probably safe to say, Miles and Robert Callow are two different people entirely, just coincidental that their stories were the same and they had the same first name being Robert!

Think Jean C's theory sounds pretty good....especially with the name "Miles" being now being found to be linked to a young miner, blinded in Laxey