If you are over 40 and starting to have difficulty reading clearly, then you are probably experiencing presbyopia.
This is caused by the natural ageing process of the eye, which affects your ability to focus on close objects. The result is blurred vision and tired eyes, especially when reading in poor light.
If you already wear spectacles for distance vision, then one option is to have separate pairs of glasses for reading and distance. But this can be very inconvenient. Another option is bifocals, but these have a sudden change in focus and an obvious line across the middle of the lens.
Progressive (also known as varifocal) lenses are the modern alternative. They have gradual change in their optical power, so there is no disconcerting jump between your near and distance vision. What’s more, varifocals give you better middle distance focus and look more attractive without the dividing line of bifocals.
Another new development is the enhanced reading lens. Essentially this is a variation on the progressive concept whereby the top part of the lens is for semi close vision and the bottom part is for reading. Such lenses are particularly useful for computer work when you need to read and look up at the screen.