Dyslexia and Speed Reading: Fonts, Spacing and RSVP

Speed-reading training is not a treatment for dyslexia, and claims that it can make a dyslexic reader much faster should be ignored. Dyslexia is a difficulty with reading words accurately or fluently, and the support specialists recommend is explicit teaching of reading and spelling plus practical adjustments such as extra time and audio. On screen, special dyslexia fonts have not beaten ordinary fonts in controlled studies, while wider spacing and shorter lines have some, limited, support. The most useful thing a reading app can offer is comfort and control, not speed.

This article is general information, not a diagnosis or treatment. Tachi is not a medical or assistive product. If you think you may have dyslexia, ask for an assessment from a qualified specialist, such as an educational psychologist or specialist teacher.

What is dyslexia?

The NHS describes dyslexia as a common learning difficulty that mainly affects reading and writing. It is not linked to intelligence, it has no cure, and there is a good deal of support that helps people manage it at school, at work and at home.

In October 2025 the International Dyslexia Association (IDA) adopted a revised definition, its first major update since 2002. It keeps difficulty with word reading and spelling at the centre, says those difficulties can involve accuracy, speed or both, and describes them as persisting even with teaching that works for most learners. It also recognises that dyslexia occurs across languages and writing systems.

That last point about speed matters here. For many dyslexic adults, slow reading is not a habit to be trained away; it is part of how the condition shows itself, because recognising each word takes more effort.

Why speed-reading claims are a poor fit for dyslexia

The limit on everyone's reading speed is how quickly words are recognised and understood, not how fast the eyes move. Rayner and colleagues (2016), in the main review of speed reading, conclude that pushing well beyond a normal rate costs comprehension. For a reader whose difficulty is word recognition, that trade-off arrives sooner.

Word-by-word RSVP display brings extra problems. It sets a fixed pace whether a word is easy or hard, gives you no preview of the next word, and removes the look-backs readers use to repair a misreading. We could not find any controlled study of RSVP as a reading aid for dyslexic adults, so there is no evidence base to recommend it. If you try it, treat it as a comfort experiment at a slow pace, not as training. The format is explained in what is RSVP reading?

Do dyslexia fonts like OpenDyslexic work?

Fonts such as OpenDyslexic and Dyslexie give letters heavier bottoms or distinct shapes to make them harder to confuse. When researchers have compared them with ordinary fonts, they have not found the promised benefit.

Most of these studies involved children and measured word reading speed and accuracy rather than understanding of long texts, so they do not settle every question. But together they point in one direction: the shape of the letters makes little difference, and the spacing around them may matter more.

Do letter spacing and short lines help dyslexic readers?

There is some evidence that they can, with caveats.

• Letter spacing. Zorzi and colleagues (2012) tested 74 Italian and French children with dyslexia, aged 8 to 14. Text with extra spacing between letters (and proportionally wider word and line spacing) roughly halved their reading errors and made reading somewhat faster. The authors linked the effect to crowding: letters packed closely interfere with each other, and dyslexic readers may be more affected. Other researchers have questioned how specific the benefit is to dyslexia.
• Short lines. Schneps and colleagues (2013) tracked the eyes of 26 high school students with dyslexia reading on a phone-sized device that showed about two words per line. Compared with the same text on a tablet at about twelve words per line, they read 27% faster, made fewer fixations and less than half as many backward eye movements, with no loss of comprehension. Other factors in the study helped some students and hindered others.

Pick a clear, ordinary font you find comfortable, make the text large enough and give it room. If a dyslexia font feels better to you, use it; it is unlikely to hurt, but do not expect it to change your reading speed.

How to set up a comfortable reading screen

Comfort is personal, so test settings rather than copying a list. Here is a 15-minute way to do it with any text you need to read:

1. Choose two or three fonts to compare. Include one sans serif you know (such as Inter or your system font) and one designed for legibility, such as Atkinson Hyperlegible or Lexend. Add OpenDyslexic if you are curious.
2. Read the same kind of text in each for three minutes. Note which felt least tiring, not which looked nicest.
3. Increase the size one step at a time until it stops getting easier.
4. Try the background. Compare a white page with an off-white or sepia one and a dark one. Choose what you can read longest without strain.
5. Keep lines short. In a word processor or browser, narrow the window or use a reading view; on a phone, portrait orientation already gives short lines.
6. Use audio alongside. Text-to-speech, built into most phones and computers, lets you listen and read together, which some readers find easier on long documents.

In Tachi's reader you can make the same comparisons: it offers seven fonts, including OpenDyslexic, Atkinson Hyperlegible and Lexend, a font size from 36 to 96 pixels, and nine themes, among them paper, sepia and several dark ones. Two modes, Highlight and Pacer, keep the whole passage on screen and move a marker through it, so you keep the context and can look back. Tachi does not let you change letter spacing; for that, a browser reading view or word processor is the better tool.

If a moving marker or a fixed pace feels stressful, close the reader and read the text at your own speed. The point is comfort. Bionic-style bolding is another option people ask about; we compare it with RSVP in RSVP vs bionic reading.

Where to get real support

• Assessment. A diagnostic assessment explains your profile and is often the route to adjustments at university or work.
• Structured literacy teaching. Explicit, systematic teaching of how sounds, letters and word parts fit together is the approach the IDA promotes, and specialist tutors work with adults as well as children.
• Adjustments. Extra time, digital copies of texts, text-to-speech and speech-to-text are standard ways to reduce the load at university and work.
• An eye examination. If words blur, double or seem to move, or reading gives you headaches, see an optometrist. Visual problems are separate from dyslexia, and no app or exercise corrects them.

Many people with dyslexia also have attention difficulties; if that sounds familiar, see speed reading and ADHD. The reader settings mentioned here are listed in full in how Tachi works.