The 30-point difference between his performance and verbal scores is very significant. (You didn't say, but I imagine that his verbal scores were higher, since these are most often correlated with academic success.) However, it's the impact of that difference on his performance that's important. If he's made it through high school and SAT's with this difference, it's pretty clear that he's been able to work around or compensate for any problems that split may have caused. Poor visual perceptual skills may have affected his ability to do art, design, or geometry, but his reading has obviously not been affected, which is great news, since he's headed for a lot of it.
If his written work is weak, he may need to have assistance from the learning center at his college. If he doesn't feel that he needs help, I'd suggest that you respect his opinion in the interests of encouraging self-advocacy. However, if his teachers at school think his self-assessment is way off base, then they might be the best ones to encourage him to seek additional help at school. If he still refuses help, his college professors will ultimately help him know if he's right in thinking he doesn't need it.
Consider an intensive dose of writing help between now and the start of school (if your son will accept it). Then keep a close watch in the fall, and try to get him to fax you a couple of first papers, both before and after his professors read them. It's great when kids want to handle the work themselves. You just don't want him to fall in a deep pit early in the game.
If he hasn't used it yet, I'd recommend getting him writing software called Inspiration®. With a bit of instruction (maybe a tutor's help) he can learn to use it easily. Then, it will be his tool to use throughout school.
