The iPhone has several ways of making things easier to read. Check out the Settings->General->Accessibility. The one I use a lot is "Zoom" where you can double tap the screen with 3 fingers, and zoom in or out or drag the part of the screen you cannot see. Also setting the text size larger helps in some cases.
Or, just put on those glasses...
I already have the larger text size enabled, but anything beyond that is recognition of 'getting old', which I'm not yet ready for! I'm getting better with the glasses, I have one 'expensive' pair from the opticians, and 6 pairs of Costco readers scattered around, so normally they're within grabbing distance, but not always...