It is impossible to have pure eyes. I am 22 years old, and have spent almost that entire time in America. I have learned certain definitions for certain words, and I have learned that certain ideas are "good" and should be embraced. I have had a certain set of experiences, which have given me a particular education. These are the eyes I read through. I cannot just forget that I am a 21st century woman, and newly graduated student.
You have your own education, and your own values, and you also cannot forget your entire life.
To read without bias would be impossible--the act of looking at ink on a page and mentally turning it into meaningful language is an interpretation, and everybody will interpret according to what their life experiences are. The word "pen" refers to a writing impliment to most, but an enclosed area for animals to somebody who was raised on a farm.
Likewise, to a 21st century American, "mustard" is a spicy sandwich spread. Some may know that the seed is very small. To such a person, "faith like a mustard seed" will mean that even the smallest amount of faith is worth having, and can drastically change a life. Mustard is pretty neutral to us. We have no emotional reaction to it.
To the audience Jesus actually spoke to, though (which was not us), that would mean something else entirely. Anybody living in the Mediteranian region in the 1st Century would have had extremely different experiences with mustard. They would have lived their entire lives hearing warnings about it--that you should never let even the slightest speck of mustard into your fields, because it is a vicous weed which will overtake everything around it. Mustard is dangerous and to be treated with caution and fear. What would they have thought, upon hearing Jesus tell a crowd that the Kingdom of God is like a mustard seed? What would a Roman soldier have thought?
No, I do not read through "pure eyes" because it is impossible to do so. What I try to do is read through honest eyes. I learn as much as I can about a culture and language, and try to understand what was originally said. I do not simply listen to the end results of a 2000 year-long game of "telephone" and call myself "pure," because I accept that without question.