Illuminating retinoid flux in the neurosensory retina.

The retinoid chromophore 11-cis-retinal triggers an intracellular cascade known as phototransduction that converts light into electrochemical signals. Enzymatic regeneration of 11-cis-retinal sustains vision, prevents the buildup of toxic byproducts, and is supported largely by the retinal pigmented epithelium. Directly visualizing rapidly changing retinoid intermediates in patients with inherited retinal diseases (IRDs) could provide essential therapeutic insights. In this issue, Engfer et al. introduced a groundbreaking strategy using the mouse retina as a genetically malleable model for the mammalian eye. Using cell-specific expression of lecithin:retinol acyltransferase to trap mobile retinols, they mapped the availability of 11-cis- and all-trans-retinoids within different retinal compartments under normal and diseased conditions. Their findings elucidate retinoid distribution in the retina and highlight important differences between mouse and human Müller glia. Here, we contextualize these advances within decades of research defining the visual cycle and retinoid biology, outlining the profound implications for therapeutic development for IRDs.