Day-old chicks were used for experiments and they worn lenses with dual powers of different hyperopic and myopic defocus (from +10D to -10D combinations).   The amounts of defocus were also varied according to the relative contrast. They worn the lens for about a week and the axial length and refractive errors were examined using high resolution A-scan and retinoscopy.
Using the same principle, a randomized control trial was conducted and a number of myopic (-1D to -5D with astigmatism less than 1D) Hong Kong Chinese schoolchildren aged between 8 to 13 years were recruited. The subjects were randomly allocated to wear either the DISC contact lenses (treatment group) or the single vision (SV) contact lenses (control group). Their refractive error and related ocular parameters (e.g. axial length) were measured every 6 months for 2 years. Cycloplegic objective refraction and axial length were measured. The changes in spherical equivalent refractive error and axial length between two groups in 2 years were compared by using unpaired t-test.