Irlen Syndrome: my investigation

Someone sent me an article about a girl who ordinarily found reading difficult and fatiguing; but when she tried laying transparent colored plastic over the page or screen, she was able to read normally.

Well, that sounded intriguing; so I started looking up more about Irlen Syndrome...
...and what I read made me suspicious.
If this is a real syndrome, why does it have its own diagnosticians? And what is behind the claim that a high percentage of the population (and the vast majority of the prison population) has a reading problem that I never heard of?

There are a lot of articles online, like this one, quoting parents and teachers who say they've seen colored overlays make a big difference.
And there are a lot of articles written from a scientific perspective, like this one or this one, claiming that Irlen Syndrome doesn't exist and the overlays don't work.

So, I asked around: Who has some insight into this?

The responses that I got from people I know paralleled what I found in the articles: I heard from parents and teachers, telling me about students who found the overlays effective ("when she started wearing glasses with yellow lenses, she suddenly went from a D to an A+ average"); or about some who maybe sort of did but they weren't sure; or about a rare light-sensitive student who actually did among many with reading disabilities who didn't; and I heard from an optometrist who said she thinks it's all a very expensive placebo effect; and my friend the nurse sent me another article....

...and then the reading specialist, who happens to know everything about everything, gave a brief answer that explains everything, including the discrepancy between the scientific findings and the anecdotes.

He wrote:

For reading difficulties: if it works, and in most cases it doesn't, it fixes a symptom, not the source of the problem. Multi sensory reading is the answer.
For light sensitivity or vision loss, it can help.

So, that's my answer.

Here are links about multi-sensory reading:
Multi-Sensory Kriah - he didn't send me this link; I am promoting him; and
Multisensory Structured Language Teaching Fact Sheet

As a side note, one thing all the Irlen pro and con studies seem to agree on is that children enjoy experimenting with reading through colored cellophane.
Well, a novel kriyah activity is also something...