Purpose:
Excessive eye elongation in axial myopia is related to abnormal organisation and content of scleral connective tissue components. 7-methylxanthine increase the content of collagen as well as the diameter of collagen fibrils in rabbit sclera and may therefore hypothetically work against axial elongation in myopia. In a randomised, double-masked, parallel, clinical trial completed by 78 myopic children aged 8-13 years with a minimum axial growth rate of 0.075 mm per six months, 7-methylxanthine (400 mg per day for 12 months) reduced axial growth by 22% in children with a base-line axial growth rate of 0.075-0.19 mm per six months and by 8% in children with a base-line axial growth rate of 0.2-0.39 mm per six months compared with placebo (p-values 0.073 and 0.593, respectively). No side-effects of the treatment were found.
Methods:
After completing the trial, children from both the placebo and the 7-methylxanthine group were given the option of continued treatment with 7-methylxanthine 400 mg either once or twice per day for another 12 months. Axial length was measured with IOL-Master (Zeiss) at -6, 0, 12 and 24 months.
Results:
35 children (17 from the original 7-methylxanthine group and 18 from the original placebo group) completed 24 months follow-up (interim data). Among children with a base-line axial growth rate of less than 0.2 mm per six months (n=18), axial growth in the original 7-methylxanthine group was 0.252 mm compared with 0.421 mm in the original placebo group (p=0.05). In children with a base-line axial growth rate of 0.2 mm or more but less than 0.4 mm per six months (n=17), axial growth in the original 7-methylxanthine group was 0.486 mm compared with 0.599 mm in the original placebo group (p=0.239).
Conclusions:
These follow-up results could indicate that additional reduction of the axial growth rate can be obtained if treatment with 7-methylxanthine is continued for more than 12 months. After 24 months, axial growth in the original 7-methylxanthine group was reduced by 40% in the low axial growth stratification layer and by 19% in the high axial growth layer compared with the original placebo group.
Clinical Trial:
www.clinicaltrials.gov NCT00263471
Keywords: myopia • adenosine • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials