My reactions are not too bad at the moment I don't think, and I turned 50 last October. I agree with all the comments re. fading eyesight though.
Mind you, I spend most of my time at work in front of a computer monitor, and a large part of my leisure time either reading (usually on a kindle), watching TV, or surfing the net on a laptop. The result of all this means I have to limit myself to about an hour at a time on here or I start to lose focus (visually not mentally!).
Modern day life I suppose, but something will have to give soon, and I suspect it will be work!
Sean ;-)