This was my contribution to a discussion among autistic adults about self-injury behavior (SIB):
Twice in my life I deliberately smashed my glasses, and I consider that to be self-injuring behavior. I am extremely dependent on my glasses, simply cannot function without them. In a way, for me to smash my glasses is like making a suicide attempt. It is a physical way to say, "I need out [of here/this] now, even if the only way out is to accept non-being."
Both times, what was going on (as I remember, in a foggy way) was that people were trying to be nice and helpful to me. I needed help, but I couldn't take their presence and pressure. Because I was already overloaded (by the factors that put me in need of help), having people "aimed at me" (so to speak; that's how it felt) and pressing up against "my space" (even though not touching me physically) became literally unbearable.
Thinking back on both episodes, I can see them as farce.
My glasses are thick and very hard to smash. It's not
something you can do in a second, probably not even in
a minute. It takes a lot of whacking and plenty of
perseveration. Also, part of the self-injury involved
(besides being "blind" and feeling useless/vulnerable
for several days while replacement lenses are made)
is the monetary cost. Cutting myself (which I feel
sure I'm not ever likely to do) would at least be
cheaper, as long as it didn't require medical attention.