I'm an optometrist who does lots of different bits of children's vision, I also have a higher qualification in children's vision.
Coloured tints can help, sometimes with some children. Whether the thing called Irlen's syndrome exists?? It may just be that some children do suffer a sort of over-excitation of the brain under certain visual conditions and reducing the contrast helps.
Many people do get pattern glare, which is the sort of shimmery thing you notice with stripes - such as when you go down an escalator. If you put a coloured filter in front of your eyes, the visual sensation reduces.
When you do see an improvement with the filters, it can be quite dramatic. But it's pretty uncommon, I reckon around 1 in 25 children with dyslexia get an improvement.
Similarly behavioural optometry, also encompasses a lot of orthoptic techinques which are regularly done in a hospital environment such as convergence eye exercises, patching or exercises to strengthen extra-ocular muscles or reduce supression. Some of it though is utter guff!
Anyway, stay a little bit sceptical, especially if someone is over-promising. You want to try the overlays for at least a couple of months before forking out for expensive glasses. But, they do sometimes make a significant improvement.