American researchers have published images of cone photoreceptor cells from live human eyes, a first in the history of ophthalmology. Professors at the University of California, Davis, as well as Indiana University's School of Optometry carried out this study. These stunning images were published in the most recent edition of Biomedical Optics Express.
The main reason researchers looked into these photoreceptor cells was to figure out new ways to prevent and treat diseases like age-related macular degeneration (AMD) and retinitis pigmentosa. These particular eye diseases have a profoundly negative effect on photoreceptors. As of yet, there have been no clear images of photoreceptors in the human eye to give doctors a clear picture of what these cells are doing.
These photoreceptor cells, which are extremely sensitive to light, are naturally regenerated and disposed of every day. This daily process is sometimes referred to as "disc shedding" and "disc renewal." These American scientists were able to capture some amazing images of this natural process.
The most important function of the photoreceptors is that they transform light from the outside world into an electrical response that registers in the brain. The reason why these cone-like cells need to be discarded and replenished so rapidly is due to the fact that the light is toxic for the eye. The eye needs to know just how many cells to replenish and how many to discard so that the eye has a "Goldilocks" amount of photoreceptors at all times.
Researchers wrote that problems with the shedding/renewing cycle in the eyes could lead to a serious condition called retinal pigment epithelium (RPE) dystrophy. This disease can lead to permanent blindness if not detected early at an eye screening.
The most difficult things for researchers to capture were the end tips of the photoreceptors. These end tips, which measure only a few microns in length, have been proven to break up the photoreceptor cells once every day in the shedding/renewing process.
Both optical coherence tomography (OCT) and adaptive optics technologies were used to collect these images. By putting these two technologies together, the scientists were able to produce images that showed the length, width, and depth of the photoreceptors within the eye's retina. In total, the doctors took pictures from three people's eyes.
To figure out how the photoreceptor cells moved through time, the team had to devise an intricate algorithm. By plugging in the data collected from the images, this algorithm allowed the team to make observations about both the spatial and temporal properties of this shedding/renewing process.
Although researchers have been looking into photoreceptors for many years, this was the first time scientists were able to produce images directly from the eyes of live human subjects. Thanks to this latest round of photos, the days when researchers were only able to collect photoreceptor data from dead animals' eyes is a thing of the past.