Nearsighted (myopia): can't see things well at a distance but close objects are seen clearly; refractive powers of the eye are too strong; often occurs early in life (first 2 decades)
Farsighted (hyperopia): can't see things well up close but distant objects are seen clearly; refractive powers of eye are too weak; relatively uncommon
Presbyopia: loss of ability of lens to change shape (accommodate) that occurs w/normal aging ( > 40); results in impaired ability to clearly view images up close (e.g. w/reading)
Astigmatism: abnormal curvature of cornea so that items far or near are out of focus