Adaptive optics (AO) imaging of the human retina is an emerging clinical technique that confers the highest possible spatial resolution of this tissue . To support consistent imaging performance across time and devices, we have designed and fabricated a robust and user-friendly phantom that can determine lateral resolution and contrast with 3D-printed microstructures approximating cone photoreceptors. We have carefully characterized multiple copies of this phantom via microscopic imaging and metrology, and we also demonstrated the phantom's utility with two different AO imaging modalities. Our results indicate that this phantom, with its associated ground truth data, can be a very effective qualitative and quantitative evaluation tool for ophthalmic AO devices.