There's no evidence that Comic Sans works well for dyslexics; it appears to be a myth.
There are a ton of commonly used fonts that are great for dyslexia, like Helvetica, Courier, Arial, and Verdana. The biggest factor in readability for dyslexics isn't font anyway, it's context: for example, the line height and kerning, the amount of white space on the page, the colors and contrast, and the design grid of the page. No font alone is going to be able to address the bigger factors, although they can certainly help.
For what it's worth, there's information here: https://creativemarket.com/blog/2014/05/14/is-comic-sans-easier-for-dyslexic-users-to-read about a study that found the four above-mentioned fonts worked well for dyslexic readers.
It didn't test Comic Sans, but it did test OpenDyslexic, which was inspired by Comic Sans. They found that OpenDyslexic did not perform as well as the others mentioned because it caused fixation.
At least one dyslexic blog noted, as well, that the study doesn't necessarily demonstrate that these commonly used fonts are better; it may also be the case that if dyslexic readers have experience using a particular font, it is easier for them to read text in that font in the future.
The study itself can be read here: http://dyslexiahelp.umich.edu/sites/default/files/good_fonts_for_dyslexia_study.pdf
Or on one of the authors' websites, which also includes the study in a slideshow format:
Their main conclusion is that font types do have an impact -- which is interesting, because we tend to leap straight past "do font types have an impact" all the way to "which ones", possibly partly because it's the easiest thing to change in a document. Their strongest findings seem to be that use of italic fonts in general and Arial Italic in particular should be avoided because they decrease readability (with the Arial version "significantly decreasing" it).
Also, they note that reading out loud is what would be most likely to improve with specially designed fonts like OpenDyslexic, and that they did not do an out loud test. I didn't see anything about WHY that's all that would improve with specially designed fonts, though.