f-ORG(ing) Ahead

Scientists from Poland’s International Centre for Translational Eye Research have introduced f-ORG (photopic flicker optoretinography), an imaging technique that detects tiny, light-induced changes in photoreceptors.

To create “flicker optoretinography” (f-ORG), the team combined optoretinography (ORG) with spatiotemporal optical coherence tomography (STOC-T), a high-speed imaging system that records nanometer-scale movements in the outer segments of photoreceptor cells. Using flickering light stimulation, the study measured how photoreceptors physically change in response to light.

The researchers confirmed that when photoreceptors are exposed to flickering light, the cones in the human retina will lengthen and contract in response to the stimulus. Similarly, in rodent models, rods also displayed elongation and contraction patterns, suggesting that this response is universal across different species.

The study identified a crucial protein, phosphodiesterase 6 (PDE6), as a key player in these structural changes. The researchers found that PDE6 undergoes shape changes at the molecular level, which amplifies the movement of photoreceptors from an atomic scale to a visible cellular scale.

To test PDE6’s role further, the study used sildenafil (Viagra), a drug known to inhibit PDE6 activity. In mice treated with sildenafil, it was observed that the usual elongation of rods in response to light was significantly reduced, confirming PDE6's essential function in photoreceptor movement.

The ability to measure these subtle changes in the retina non-invasively opens up possibilities for diagnosing retinal diseases like macular degeneration and retinitis pigmentosa, the authors say. Since f-ORG can detect early functional changes before visible damage occurs, it could become a valuable diagnostic tool for monitoring treatments and detecting vision loss sooner.