It's an interesting question - I did a bit of digging and found some papers that mention it, however there's limited empirical evidence actually suggesting or examining this area from what I can tell. A recent review about internet gaming disorder (IGD) as an emergent health concern for men by Chen and colleagues (2018) discusses eye strain. However when you look at the refence they cite a Young paper from 2009, that discusses it's something to look out for without any citation or empirical evidence.
A systematic review of IGD (2018), indicates that there isn't much evidence to support a strong link between poor physical health and IGD, despite gaming being a passive activity as well. It didn't mention anything about vocabulary and language. From what I can tell, this is either an understudied area or there isn't much of a link between these things (and negative results tend not to get published). Anyone else find anything different?