The study investigated how orthokeratology lenses (OK lenses) of different sizes affect eye length growth in myopic children compared to regular glasses. 162 children wearing OK lenses (86 with a diameter of 6.0 mm and 76 with a diameter of 5.5 mm) and 68 children wearing single vision spectacle lenses who wore the lenses continuously for at least one year were included in the research. After 12 months of lens wear, significant differences in axial elongation of the eye were found between the groups. Median axial elongation was reduced by 78% (from 0.295 mm to 0.065 mm) in the 5.5 mm diameter group and by 53% (from 0.295 mm to 0.140 mm) in the 6.0 mm diameter group compared with wearing glasses. Among patients with OK lenses, axial elongation was significantly reduced by 54% in the 5.5 mm group compared to the 6.0 mm group. The study concluded that orthokeratology lenses effectively inhibit eye length growth in myopic children and achieve better myopia control than regular glasses, with smaller diameter lenses being more effective.