Direct laser writing of a titanium dioxide-laden retinal cone phantom for adaptive optics-optical coherence tomography

The spatial resolution of adaptive optics-optical coherence tomography (AO-OCT) enables visualization of retinal components (e.g., photoreceptors), which can advance clinical diagnosis of ocular diseases. Currently, however, variability in AO-OCT system performance suggests a need for standardized physical models, or “phantoms”, that replicate the opto-structural properties of retinal components. Here we employ direct laser writing – a two-photon polymerization-based additive manufacturing technology – using a light scattering titanium (IV) dioxide nanoparticle-laden photomaterial to create novel retinal cone outer segment (OS) phantoms. Fabrication results demonstrate effective mimicry of cone OS diameter and spacing at four retinal eccentricities, while AO-OCT experiments demonstrate cone spacings >4 µm can be resolved. These results suggest a promising methodology for biomimetic photoreceptor phantom development for AO-OCT.