A new mutant line (delayed amelanotic-DAM) of domestic chicken shows an early progressive loss of choroidal and pigment epithelial melanin which leads to visual impairment, blindness and severe retinal dystrophy. Ocular amelanosis begins with an initial destruction of choroidal melanocytes, usually accompanied by choroidal inflammation. Following complete loss of chor oidal melanocytes, RPE shows a variety of pathological changes which appear to represent successive stages and include thinning, retraction, clumping, and destruction of apical processes and RPE cells. Retinal detachment, loss of cells and retinal laminar organization occur in the inner retinal layers in advanced cases of ocular amelanosis.