(A). Spectacle lenses [minus 15 D (–15) or plus 15 D (+15)] were applied to the right eyes of chicks for 6–24 hr. (B). Schematic diagram illustrating the effects of imposed optical defocus on the location of ocular images of distant objects for an emmetropic eye (center); positive lenses move the image plane in front the retina, imposing myopic defocus (left), while negative lenses move the image plane behind the retina, imposing hyperopic defocus (right). (C) Refractive status of chick eyes while wearing –15 D and +15 D lenses. Application of –15 D lenses results in a hyperopic shift in the refraction of normal chick eyes, relative to untreated (no lens) eyes, whereas application of +15 D lenses results in a myopic shift in refraction, compared to untreated eyes. ***p<0.0001, ANOVA with Bonferroni correction for n=2 chicks in each group (five measurements/chick). (D) IL-6 mRNA expression in choroids from control and treated eyes, following 6 or 24 hr of plus lens wear (n=6 and n=27, respectively), 24 hr of minus lens wear (n=34), and normal untreated choroids (n=8). ***p=0.0003, Wilcoxon signed-rank test for matched pairs. (E) Scleral proteoglycan synthesis following 24 hr of lens wear. Proteoglycan synthesis was significantly reduced following 24 hr of + 15 D lens wear, compared to untreated contralateral control eyes (***p=0.00047, paired t-test, n=10) and was significantly increased following 24 hr of –15 D lens wear, compared with untreated contralateral control eyes (*p=0.0403, paired t-test, n=13).