SIGNIFICANCE: The myopia control effect of orthokeratology accrues over time, with 11 years of lens wear providing a cumulative absolute reduction in axial elongation of −0.69 mm in comparison with spectacle lens wear. Steeper corneas are likely to benefit from enhanced myopia control efficacy. PURPOSE: To compare axial length growth between a group of orthokeratology contact lens wearers and a control group of distance single-vision lens wearers over an 11-year period. METHODS: White European subjects 6 to 12 years old with myopia −0.75 to −4.00DS and astigmatism ≤1.00DC were prospectively allocated orthokeratology or distance single-vision spectacle correction for 2 years. Axial length measurements (Zeiss, IOLMaster) were taken at 6-month intervals during the initial 2 years of the study. Subjects were contacted approximately 5 and 9 years later (i.e., 7 and 11 years after the beginning of the study, respectively) and axial length measurements were repeated. RESULTS: Thirty-one orthokeratology and 30 control subjects were initially recruited, but only 10 orthokeratology and 15 control subjects attended the 11-year visit. In comparison with the control group, the change in axial length for the orthokeratology group was reduced by 0.04, 0.10, 0.14, 0.22, 0.45, and 0.69 mm after 0.5, 1, 1.5, 2, 7, and 11 years of lens wear, respectively. Significant differences between groups were found in mean unadjusted changes in axial length at the 1-, 1.5-, and 2-year time points (unpaired t-test, p < 0.05), whereas standard contrasts revealed statistical differences between groups in the estimated marginal means of the change in axial length at the 7- and 11-year time points (p < 0.05). CONCLUSIONS: Eleven years of orthokeratology lens wear provided a substantial slowing in the axial elongation of the eye, with a treatment effect of up to 0.69 mm after 11 years of lens wear in comparison with single-vision lens wear.