Presbyopia is an eye condition where the eye loses its ability to focus on nearby objects. It is an age-related change that typically begins in the early 40s. What happens is the crystalline lens within the eye gradually loses its ability to flex. That makes it difficult for the eye to focus light onto the retina.
You can tell if you have the early signs of presbyopia when you start holding objects further away to see them and/or if you are experiencing eye fatigue and headaches.