The retina is nourished by two unique (retinal and choroidal) circulations. The lack of depth-resolved blood volume (BV) imaging techniques hampers investigation of vascular-specific regulation of the retina in vivo. This study presents a high-resolution, laminar-specific magnetic resonance imaging (MRI) study to image retinal and choroidal BVs, their responses to physiologic challenges in normal and Royal-College-of-Surgeons (RCS) rats (a model of retinal degeneration). Retinal and choroidal BVs were imaged by MRI (30×30×800μm) with intravascular administration of monocrystalline iron oxide nanocolloid (MION) contrast agent. Relative baseline BV and BV changes due to physiologic challenges were calculated in normal and RCS rat retinas. BV-MRI revealed two well-resolved retinal and choroidal vascular layers located on either side of the retina and an intervening avascular layer. The ratio of choroidal:retinal BV in normal rats at baseline was 9.8±3.2 in control rat retinas (N=7). Hyperoxia decreased retinal BV (−51±17%, p<0.05) more than choroidal BV (−28±14%), and hypercapnia increased retinal BV (52±11%, p<0.01) more than choroidal BV (12±11%). BV-MRI in degenerated retinas of RCS rats (N=7) revealed thinning of the avascular layer and an increase in relative baseline retinal and choroidal BVs. Only hypercapnia-induced BV changes in the retinal vasculature of RCS rats were significantly different (smaller) from controls (p<0.05).These findings suggest that BV in both retinal vasculatures is regulated. The relative baseline BV in both vasculatures increased in retinal degeneration. BV-MRI provides clinically relevant data that may prove useful for early detection and longitudinal probing of retinal diseases, and could complement optical imaging techniques.