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Abstract: This study evaluated the efficacy of a facemask, a non-invasive and potentially more reliable method, in inducing axial myopia in guinea pigs. Thirty-six animals were randomly assigned to 3 groups: MDF (monocularly-deprived facemask, n=6), lid-suture (eyelids sutured monocularly, n=24) and normal control (free of form deprivation, n=6). All the groups underwent biometric measurement (refraction, corneal curvature and axial length) prior to the experiment. All animals in the MDF group underwent biometric measurement at each of the 4 timepoints (2, 4, 6 and 8 weeks of form deprivation). In the lid-sutured group, the animals were randomly assigned to 4 subgroups (n=6 each) and each subgroup underwent biometric measurement at one of the timepoints matching those of the MDF group. In the normal control group, all animals underwent biometric measurement at each of the timepoints matching those of the 2 experimental groups. Placement of a facemask on an animal took approximately 10sec and all the facemasks remained in place at all timepoints. The procedure of lid-suture took at least 20min for an animal and rupture of the sutures occurred in 50% of the animals after 4 weeks. The MDF eyes developed myopia from −2.21±2.11D (Mean±s.d.) at 2 weeks to −4.38±2.14 at 8 weeks (p<0.05 at all timepoints, compared to the contralateral eyes) with a lengthening of the vitreous chamber from 0.17±0.05mm at 2 weeks to 0.29±0.12mm at 8 weeks (p<0.01 at all timepoints, compared to the contralateral eyes). The lid-sutured eyes developed myopia from −2.38±1.21D at 2 weeks to −4.75±1.39D at 8 weeks (p<0.05 at all timepoints, compared to the contralateral eyes) with a lengthening of the vitreous chamber from 0.13±0.02mm at 2 weeks to 0.30±0.10mm at 8 weeks (p<0.05 at 2, 4, 8 weeks, but >0.05 at 6 weeks, compared to the contralateral eyes) and an increase in the radius of the corneal curvature (0.20±0.07mm at 4 weeks, p<0.01; 0.17±0.05mm at 8 weeks, p<0.05; compared to the contralateral eyes). Both the MDF and lid-sutured groups had a similar development in myopia and vitreous length (MDF vs lid-suturing: p>0.05 at all timepoints, one-way ANOVA with Bonferroni correction). This development was significantly faster than in the normal control group (MDF or lid-suture vs normal control: p<0.05 to <0.01 from 2 to 8 weeks, one-way ANOVA with Bonferroni correction). The radius of corneal curvature in the lid-sutured group was significantly greater than in either the MDF group or the normal control group since 4 weeks of form deprivation (p<0.05, one-way ANOVA with Bonferroni correction). Treatment with MDFs is as effective as the lid-suture in inducing axial myopia in guinea pigs. This method is non-invasive and allows evaluation of the same group of animals at different timepoints so that the number of animals required could be minimized without affecting the accuracy of the results. [Copyright &y& Elsevier]