How many alternates can we have to each character in the alphabet in Open type and what limits it to this number?

The format allows tens of thousands of glyphs in a font, so there are potentially more than enough for every character of the alphabet.

However, the choice of stylistic sets occurs as a typesetting choice — it’s not in the document “reader” available to the end user.
Therefore, a practical system would have a variety of different fonts, for different kinds of dyslexia, which the reader could choose from in the Preferences menu of, for instance, Safari. So this would work better in a dynamic online environment, rather than with PDF documents.

But, if end users download a text file into a program such as Word, then they can set and print it in *their* optimal font.

Could a typeface be preference based with individual settings for each user or is the best way to go about this creating a programme which renders each character in the alphabet based on a set of questions for the user?

The foundry could provide a series of fonts geared to different kinds of dyslexia.

But doesn’t this situation exist already?
Aren’t there a kazillion fonts available, and can’t readers simply choose the one that works best for them?
Why do advocates try to start from scratch rather than analyzing and exploring the typefaces that already exist?
Why not do research that categorizes different forms of dyslexia, and find the typefaces that works best for each?
And only then attempt to refine those “best practice” solutions.

It seems to me that technology could probably help here, not so much by creating fonts with letters that remain recognizable when altered, but by altering the entire display to compensate for the common problems faced by dyslexic readers. 3D acceleration could dynamically distort the screen in a way that compensates for a reading disability. Users could even dynamically alter their distortion method on the fly, and save profiles for a methodology that works best for them.

Granted some fonts are more difficult to read. Because any visual difficulties are in fine detail the size of the font can be more important. Most dyslexics really have no visual problems as far as reading print. Most problems are in fact word processing problems unrelated to vision.

I sell See Right Dyslexia Glasses that are able to remove all visual distortions that make reading diffficult for visual dyslexics. More info at dyslexiaglasses.com.

When doing my research I found that the majority of dyslexics will respond that they see a page of print in a clear, stable, focused and uniform manner.

The idea that there are problems that are common to all dyslexics doesn’t seem to fit the current data. Reading is a complex process that needs to have many different factors all work properly. Failure of any factor can result in reading difficulties that can be classified as dyslexia. Visual problems are only one factor in dyslexia and affects a minority of dyslexics.

A major problem for dyslexics is trying to determine what will help them read better when almost all treatments claim to help all dyslexics. I limit my claim so that it is always true. I claim that for the dyslexic that can describe a visual problem that makes reading difficult the See Right Dyslexia Glasses will remove that problem.

The reason some visual dyslexics are not identified until the third grade is that is when the print size is reduced.
Dyslexics who find they do not have problems reading billboards are more likely to be visual dyslexics. Dyslexics that have their normal reading problems reading billboards are more likely to have language processing problems.

Endre,
I’m just curious: Can you give an example how a letter should be designed for two different types of reading disabilities?
I always like to believe that legibility/readability affects everybody the same. I find it hard to believe, that a special typeface for dyslexics is helpful, when every other typeface they see in their environment is designed differently. But I have no experience in this field whatsoever.

A possible lead