I have always enjoyed very good eyesight. However, in the last 5 years or so I need glasses to read in poor light. Night time and under electric lights it is far worse. Bright natural light I am so much better. Incidentally after holidaying abroad enjoying lots sunshine and little computer use my eyesight is really very good. Is it due to the extra sunshine I have had or little computer use? But yes, I would say it is normal with age. Maybe get your eyes tested if you feel really concerned though.
I've got another 'keen'... Ouch!