Although you didn't say, I guess that you usually wear eye glasses. 

I know that some old (film) SLR cameras allow a correction eyepiece accessory that compensates to your eyesight. 

I Googled for slr eyepiece diopter and found over 90,000 hits. 

There are also some variable dioper accessories in case you are not sure what diopter value to buy. 

--
Martin