This is the 13172nd most frequent German word.
anstrengen
"Anstrengen" means "to exert" or "to make an effort."
Here, 'anstrengen' is used reflexively ('mich anstrengen'), indicating putting a lot of effort into achieving something.
Ich muss mich anstrengen, um die Prüfung zu bestehen.
I have to exert myself to pass the exam.
In this case, 'strengt an' implies that the subject (the work) is causing fatigue or effort to the speaker.
Diese Arbeit strengt mich wirklich an.
This work is really exhausting me.
Here, 'anstrengen' is used with 'Ihre Augen' (your eyes) to convey the act of straining them, often in a physical manner.