A metabolite of caffeine may slow the progression of myopia in children, a preliminary study has found, researchers report today.
If large clinical trials find 7-methylxanthine (7-MX) safe and effective, it could become a valuable treatment for myopia, which is associated with a heightened risk of conditions that affect vision and eye health, including macular degeneration, cataracts, glaucoma and retinal detachment, according to the Danish researchers.
7-MX has been used since 2009 to treat childhood myopia in Denmark, but it has not been fully evaluated in long-term studies.
Writing in the latest edition of *The British Journal of Ophthalmology*, the researchers describe reviewing the medical records of 356 girls and 355 boys treated for myopia at one eye clinic in Denmark between June 2000 and January 2021.
The children underwent comprehensive eye tests, including measurement of axial length, and 624 of took up to 1200 mg daily 7-MX tablets (average 470 mg) while 87 did not.
Their average age was 11 when they started treatment and their eye length and degree of myopia were tracked for an average of 3½ years.
The average degree of refractive error to begin with was ?2.43 D, which increased by an average of 1.34 D during the monitoring period. -3.00 D is regarded as moderately severe myopia; -6 D or more is regarded as severe myopia.
Average axial length was 24.4mm, to start with, increasing by an average of 0.21 mm/year.
However, the researchers, led by Dr Klaus Trier, of Trier Research Laboratories, Ojenlage Klaus Trier ApS, Hellerup, found 7-MX treatment was associated with a slower rate of worsening myopia and axial elongation. Higher doses were also more effective.
Based on the data, the researchers estimated that for a typical seven year old with an initial refractive error of ?2.53 D, the child’s myopia would increase by ?3.49 D over the following six years without treatment.
But that could slow to -2.65 D over the same period if they took a daily dose of 1000 mg of 7-MX.
Similarly, without treatment the axial length would increase by 1.80 mm over six years compared to 1.63 mm if the child took a daily dose of 1000 mg.
None of the children taking 7-MX reported any side effects during the monitoring period.
While the study was observational, the research team write: “Existing myopia control intervention methods are not fully effective in preventing children from progressing to high myopia, and 7-MX may become a valuable supplement if causality and efficacy can be confirmed in future randomised controlled trials.”
Trier K, Cui D, Ribel-Madsen S et al. Oral administration of caffeine metabolite 7-methylxanthine is associated with slowed myopia progression in Danish children. *British Journal of Ophthalmology* 23 August 2022; doi 10.1136/bjo-2021-320920
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