Your vision may be blurry for different reasons.  Blurry vision may be caused by the need for glasses, or what is called refractive error, or may be caused by medical eye problems such as cataracts, diabetes, glaucoma and macular degeneration.   Medical eye problems require a correct diagnosis and appropriate medical management to prevent permanent vision loss or blindness. 

It is very important to see an eye care professional to figure out what the problem is.  The most common cause of constant blurry vision is refractive error.  This includes being nearsighted, farsighted, having astigmatism or being unable to read after the age of forty. 

The technical terms for these conditions are myopia, hyperopia, astigmatism and presbyopia.  Myopia, the most common is where the eye is too long relative to the focusing power off the cornea and lens leading to a blurry image on the retina.  

Hyperopia is the opposite problem.  The eye is too short for the focusing ability of the cornea and lens, creating a blurry image on the retina.  In hyperopia, however, the eye can be partially correct the problem by focusing the internal lens using the ciliary muscles.  This often leads to eye strain and blurry vision that becomes clear and blurry throughout the day. 

Astigmatism creates a distinct type of blur as a result of the cornea not being exactly spherical in shape.  This results in two meridians of focus that don’t come together creating a blurry image on the retina. 

Presbyopia is the universal decreased ability of the eye to focus at near after the age of 40.  All these refractive conditions can be corrected for the most part with glasses and contact lenses after your eyes are examined and a proper diagnosis is made.