Two of my kids were not really reading in K.
In the first case, dd (now 8) is both a visual learner and also had visual processing issues - eye tracking/eye teaming - that were fixed with six months of vision therapy during first grade. However, I just found out the other day that she's reading right at grade level now (3rd) and honestly I'm a little disappointed. We did IQ testing during K, so I have a rough idea of her potential, though I might like to re-test. I'm not sure if it's a case of her not really trying harder stuff, or whether her talents simply lay elsewhere (she's a grade level ahead in math according to a recent MAPS test, whatever that is. But still, even in that area I believe she's capable of more).
In the other case, my ds (now in first grade) has had some special needs issues - had an IEP for speech and fine motor. At the start of K he didn't really know the sounds of all the letters. Now he's more than a grade level ahead in reading - though his teacher recently noted that he does not perform well re: comprehension when the test is timed, in which case he tests at a level close to the end of first grade. He can read timed, or he can have good comprehension, but not both. He too is a VERY visual learner. He's definitely more gifted than his sister. He has not yet had IQ testing yet.
Other than something like a vision check (perhaps with a behavioral optometrist to check how the eyes work together, in addition to a regular vision check, see
www.covd.org ), I think mom2boys is right, sometimes you just have to be patient!