You are at an advantage ... when one focus's on text, more than likely the conscious mind is involved ... ya know the analytical side of the mind.
By taking off your glasses, and not being able to focus, this should help to involve the sub-conscious more easily. The ideal situation to be in!
Of course, the blur may not be recognized by the mind and may process the material as something totally different! IE you PR a book on computers but information is read as something having to do with accounting ... now your in trouble!
But what it boils down to is ... as Pete reiterated, you should be 'comfortable' with the process.