August 23, 2022
A metabolite of caffeine, known as 7-MX, may slow the progression of myopia, also known as myopia, in children, suggests observational research published online in the British Journal of Ophthalmology.
If proven safe and effective in large clinical trials, 7-MX could become a valuable treatment for a condition for which current options are somewhat limited, the researchers say.
Myopia occurs when the eye becomes too long, stretching and thinning, and often begins at age 6-7, progressing to age 16-20.
It is associated with an increased risk of several conditions that affect vision and eye health, including macular degeneration, cataracts, glaucoma, and retinal detachment.
Preliminary research suggests that the caffeine metabolite 7-methylxanthine, or 7-MX for short, inhibits excessive elongation of the eye (axial elongation).
7-MX has been used to treat childhood myopia in Denmark since 2009. But until now it has not been fully evaluated in long-term studies, and the researchers wanted to find out how quickly myopia progresses in children who they take 7-MX.
The researchers reviewed the medical records of 711 children (356 girls and 355 boys) treated for myopia at the one-eye clinic in Denmark between June 2000 and January 2021.
Comprehensive eye examinations, including axial length measurement, were performed on the children. And 624 of the children took 7-MX tablets up to 1200 mg per day (average 470 mg), while 87 did not, for various reasons.
Their mean age was 11 years (range 7–15) when they started treatment, and eye length and degree of myopia were followed for a mean of 3.5 years (range 11 months to 9 years).
Diopters (D) are the units of measurement used to assess the extent of eye function: the average degree of refractive error (short-sightedness) to begin with was -2.43 D, which increased an average of 1.34 D during the follow-up period. -3.00 D is considered moderately severe myopia; -6 D or more is considered severe myopia.
The mean axial length was 24.4 mm to begin with, increasing by an average of 0.21 mm/year.
Treatment with 7-MX was associated with a slower rate of myopia worsening and axial lengthening, with higher doses apparently more effective.
From this data, the researchers estimated that for a typical 7-year-old child with a refractive error of -2.53 D to begin with, that child’s myopia would increase by -3.49 D over the next 6 years without treatment.
But with a daily dose of 1000 mg of 7-MX, the myopia of the same child would increase by -2.65 D over the next 6 years.
Similarly, without treatment, the axial length would increase by 1.80 mm over the next 6 years, while it would increase by 1.63 mm with a daily dose of 1000 mg.
The researchers calculated that, on average, for an 11-year-old child taking 1,000 mg of 7-MX daily, that child’s myopia would increase by -1.43 D over the next 6 years, compared to – 2.27 D without treatment. And the axial length would increase by 0.84 mm compared to 1.01 mm without treatment.
None of the children taking 7-MX reported any side effects during the control period.
The findings echo those of experimental studies, the researchers say. But they acknowledge that their study is observational, and they weren’t able to take into account potentially influential factors, such as genetic factors, time spent outdoors, ethnicity and time spent at nearby work. Therefore, their findings cannot establish causality.
“The question of causality and the size of a potential treatment effect can only be determined by a randomized trial,” they write.
But they conclude: “Existing myopia control intervention methods are not entirely effective in preventing children from progressing to high myopia, and 7-MX may become a valuable adjunct if causality can be confirmed and the ‘efficacy in future randomized controlled trials’.
Source:
Journal reference:
Trier, K., et al. (2022) Oral administration of the caffeine metabolite 7-methylxanthine is associated with slowed myopia progression in Danish children. British Journal of Ophthalmology. doi.org/10.1136/bjo-2021-320920.