The change of peripheral refraction and the shape of 52 myopic eyes of 26 patients aged 8 to 16 (averagely, 10.4 ± 0,9 years) resulting from overnight wearing of orthokeratology lenses was followed up for 3.2 ± 0.9 years on average. The use of Ortho-k lenses was found to form relative peripheral myopia, whose value correlated with the initial degree of myopia and was averagely equal to -1.4 ± 0.13 D, -1.9 ± 0.17 D and -4.4 ± 0.13 D, respectively for low, moderate and high myopia. The ratio coefficient APA/HD between the length of the anterioposterior axis (APA) and the horizontal diameter (HD) of the eye changed from the initial value, which was averagely equal to 1.01 ± 0.06 (1.00 ± 0.002 for low myopia, 1.01 ± 0.008 for moderate myopia, and 1.02 ± 0.003 for high myopia), to -0.98 ± 0.006 (-0.94 ± 0.001 for low myopia, 0.98 ± 0.007 for moderate myopia, and - 1.00 ± 0.006 for high myopia) by the end of lens wearing term. This dynamics of APA/HD variation is an evidence of eyeball shape change as a result of prolonged use of ortho-k lenses toward the shape of a oblate ellipsoid. This is accompanied by the formation of a peripheral myopic defocus // Russian Ophthalmological Journal, 2016; 1: 62-6