Choroidal modulation of refractive state. A. Unfixed hemisected chick eyes. Arrowheads delimit choroidal boundaries. B. Plastic-embedded sections of the back of the eyes. L, lacuna; P, pigment cells; PE, retinal pigment epithelium; arrowhead, choriocapillaris. C, One-mm-thick section of the posterior eye wall. Ch, choroid, delimited by arrows. Reproduced with permission from Wallman et al., 1995 © Elsevier. D. Thickness of the retina+choroid as a function of retinal defocus induced by spectacle lenses. Reproduced with permission from Wildsoet & Wallman, 1995 © Elsevier.