There doesn't seem to be a limit on how many times you can open the spyglass every second.

This could be problematic as every time you open the spyglass about half the screen goes black.

These two things together allows you to make you screen flicker from pitch black to a much lighter color at least 15 times every second which would probably be considered strobe lights and might be harmful to those with photosensitive epilepsy.

While this might seem like it wont ever come up in gameplay, there are actually quite a few people like me who can click at least 15 times per second without external tools.

This could be fixed by either limiting the amount of times you can use the spyglass in a brief amount of time OR by making a smooth transition to the spyglass's black outlining instead of it instantly appearing.

The video linked shows the oversight and/or bug in action.

Also, this doesn't happen if your max framerate is less than 20 as most of the times the spyglass flickers wont appear to you