Irlen, Dyslexia, struggling learners, vision problems in learning

I was at soccer practice with my grandson.  This is the only time I have been all season.  Another mother was there with a young child.  She is homeschooling for the first time this year.  We were comparing ideas on schooling and she has a child who is struggling in school.  I told her about my child having Irlen dyslexia.  She and I planned a time for her to come see how I tutor.   When she looked up the Irlen online, her daughter said her words moved like the third example.  She went to an educational store, Mardel's, and allowed the child to pick out a plastic color sheet to place over her school work.  On one of the store end caps there was a magnifying glass with pink and black zebra stripes.  Her daughter asked to have one.  When her daughter put it on her paper to read her comment was, "This cages the letters so they cannot escape."   In three weeks, reading was on level.
Her mom had said many times, "I do not understand why you cannot get this," when she was teaching this child.
How many children would benefit from being able to see correctly?  How many are we labeling learning disabled or teaching ineffectively because they cannot see or cannot see correctly?