Microscope equipped with mirrors and a laser reveals the back of the retina in real time.

A new type of laser-based microscope can quickly provide a real-time view of living cells in the human retina.

For more than three decades, researchers have probed the human eye with laser-scanning microscopes. These devices use swivelling ‘scanning’ mirrors to direct a laser across a sample and create an image. This method can resolve some individual retinal cells, but imaging of the retina’s central cone cells — which are responsible for the perception of fine detail — usually requires either subsequent processing or complex and specialized equipment.

Joseph Izatt and his colleagues at Duke University in Durham, North Carolina, devised a series of mirrors and lenses that first expands the image formed from the laser light, then redirects the image across the scanning mirrors before it reaches a camera. These steps result in more accurate placement of the laser light onto the camera sensor, resulting in a sharper image.

A human retina (left) imaged by a conventional approach looks blurrier than when imaged by a microscope equipped with additional mirrors and lenses.Credit: T. B. DuBose et al./Nat. Photonics

The technique improves resolution over conventional methods and is much faster. When the setup was used on a living person’s eye, the microscope captured a real-time video of the retina, including clear footage of individual cone cells.