Abstract
Mitochondria are cellular organelles chiefly intended for energy production. Mammalian photoceptors aggregate numerous mitochondria in the ellipsoid region immediately adjacent to their light-sensitive outer segments to support the high metabolic demands of phototransduction. However, these complex, lipid-rich organelles are also poised to affect the passage of light into the outer segment, an essential step in the transduction of physical energy into cellular signals. Here we show, via live-imaging and computational modeling, that despite this risk of light scattering or absorption, such tightly packed mitochondria concentrate light for entry into the outer segment. Intriguingly, this “microlens”-like feature of cone mitochondria delivers light with an angular dependence akin to the Stiles-Crawford effect (SCE), providing a simple explanation for this essential visual phenomenon that improves resolution. Given the pivotal role that photoreceptor mitochondria play in multiple retinal degenerative diseases, this new insight into their optical properties provides critical information for the accurate interpretation of non-invasive ophthalmic imaging results and lends support for using SCE as an early diagnostic tool.
Funding: NEI Intramural Research Program