If you learn PhotoReading on the physical books (a necessity I have found). You know how to achieve photo focus on the computer. Nothing required. Besides you can PhotoRead two pages at a time on the computer with most pdf files and acrobat reader.
I prefer to download my kindle books onto kindle for PC for PhotoReading. Although it only has a single page it is much faster and easier to PhotoRead on PC or Mac than ebook and other tablets.
Patrick if you want to use dots, you only need to 1 inch 2.5cm apart. Top middle alignment to your page in the browser. (cocktail wienie effect).
However it's much easier if you've got the knack of getting into focus playing with magic-eye 3d Sterograms. After playing with them in print form it's a step to get into seeing them on the computer. Once you get the focus on the computer no cues are required. You'll use both the t-technique and 3d effect.
Alex