Trust
Sources and evidence
Last updated 29 October 2026
Every key claim on this site carries two things: a numbered source and an evidence tag. This page explains both.
The four evidence tags
| Tag | Meaning | Typical basis |
|---|---|---|
| STRONG | Several good studies agree and the effect is consistent. | Randomised trials, systematic reviews and meta-analyses, large cohort studies that agree. |
| MODERATE | Good studies exist but some disagree, or the effect size is uncertain. | Fewer or smaller trials; observational studies with plausible mechanisms. |
| LIMITED | Early, small or indirect evidence; could change. | Pilot trials, short follow-up, animal or laboratory work, expert opinion. |
| EXPERIENCE | What happened in the author's own family. One account, not research. | The author's experience with his own children. |
The grades follow the evidence register in Appendix B of the book, where every claim in the book is listed with the strength of the evidence behind it.
Which sources we rely on
In rough order of weight: systematic reviews and meta-analyses; randomised controlled trials; the International Myopia Institute white papers; guidance from the American Academy of Ophthalmology, the American Academy of Pediatrics, the American Association for Pediatric Ophthalmology and Strabismus, the American Optometric Association, the US Preventive Services Task Force, the UK National Institute for Health and Care Excellence and the World Health Organization; large cohort studies; then smaller studies, clearly labelled as such. News articles, blogs and product pages are not sources.
Opened and read
A reference is listed only if it was opened and read against the sentence it supports. Where a claim could not be verified, the sentence was removed rather than softened. Each article lists its own sources at the end, with links where the source is online.
Conflicts of interest
The author has no financial relationship with any lens, drop, device, supplement or clinic. The site's only commercial interest is the author's book.
Found an error?
If a source does not say what we say it says, tell us via the contact page. Corrections are logged on the corrections page.