6-HYDROXY DOPAMINE DOES NOT AFFECT LENS-INDUCED REFRACTIVE ERRORS BUTSUPPRESSES DEPRIVATION MYOPIA

Degradation of the retinal image by translucent occluders during postn atal development induces axial myopia in chickens, tree shrews and mon keys. Local visual deprivation produces myopia even in local regions o f the eye and neither accommodation nor intact connection between the eye and the brain are necessary. Therefore, it is an important questio n whether a similar local-retinal pathway translating visual informati on into growth or stretch signals to the underlying sclera is acting t o emmetropize the growing eye. It is not known until now whether occlu der deprivation triggers similar eye growth (or scleral stretch) mecha nisms that are also responsible for visual guidance of normal refracti ve development. We here report that, in chickens, 6-hydroxy dopamine s uppresses deprivation-induced myopia but has no effect on the magnitud e of changes in axial eye elongation that are induced by spectacle len ses. The result suggests that, in chickens with normal accommodation, two pharmacologically different feedback loops may be responsible for deprivation myopia and lens-induced refractive errors.