Spying Inside the Eye
By Genevive Bjorn, M.S.
NEI Freelance Science Writer
Robert Fariss, Ph.D., has two loves: cell biology and microscopes. As chief of the Biological Imaging Core at the National Eye Institute (NEI), he is able to combine these interests, providing researchers with access to cutting-edge imaging technology."We can exploit the eye's transparency to take pictures of cellular processes as they happen, including the interactions between cells, or between cells and proteins," Fariss says.
The Imaging Core's latest acquisition, a two-photon laser microscope, is massive; it could easily fill a single-car garage. The foundation of this state-of-the-art microscope system is an ultra-fast pulsed laser, which can penetrate more deeply into living tissues than conventional lasers can. This microscope, however, is just one of many pieces of equipment that Fariss and his colleagues use to spy on the hidden world inside the eye.
In a recent interview, Fariss discusses his passion for cells and microscopes, as well as his experiences since joining the NEI in 2000.
For what types of projects are your high-tech instruments used?
The Imaging Core Unit assists investigators throughout the NEI who are working on a broad range of topics related to vision or blinding eye disorders. Our lab has the special capability of looking at the interactions of living cells with each other, with proteins, and with the environment.
Is there anything unique about the eye that enhances imaging?
Yes--one of the fortuitous things about studying the eye is its transparent structure, from the cornea in the front to the retina in the back. We can exploit its transparency to take pictures of cellular processes as they happen, including the interactions between cells, or between cells and proteins. We can also look at both non-living and living samples.
Why is it important to study living cells and tissues?
The cornerstone of cell biology research for the better part of a century has been looking at non-living, preserved tissue, and this continues to be a central component of our studies. But I also draw an analogy with ecology: We have learned a lot by looking at cells preserved in paraffin wax, like Darwin did when he looked at finches in boxes. But when he wanted to understand the fundamental biology underlying the birds' behavior, Darwin had to get out into the field and see how the birds were interacting with other animals in their environment. It's the same with cells. We need to understand how they interact with other cells around them.
What have you learned by watching living cells interact with their environment?
Living cells appear to monitor their external environment in a very dynamic way. For instance, when a tissue is injured, immune cells migrate toward the injury. Not surprisingly, living tissues are much more dynamic than scientists envisioned when they were looking only at preserved samples.
Robert Fariss, Ph.D.
Chief, Biological Imaging Core Unit
National Eye Institute
What challenges do you face when imaging living tissues compared to preserved?
Shining light through tissues causes photo damage, much like the sun's ultraviolet rays can cause skin damage. From a cell biology standpoint, we want to minimize the amount of damage that we cause while illuminating tissues. For living tissues, that's especially important.
How do you minimize photo damage?
Today, we use lasers with longer wavelengths of light than older technologies used. Specifically, our new two-photon laser microscope uses a longer wavelength of light than a confocal microscope, which was our standard imaging tool until now. A longer wavelength means that the light carries less energy, which causes less damage to living cells. Because the two-photon microscope minimizes disruption of cells, it will greatly expand our opportunities for live imaging.
The Imaging Core focuses on basic laboratory research, but do any of your projects involve technologies that could be used for patients in the clinic?
In the period that I've been at the NEI, ophthalmologists and basic scientists who work on visual processes have come to recognize their shared interests in improving imaging applications. Many technologies that were first used in the laboratory have made their way into eye clinics, including the traditional confocal imaging; the newer optical coherence tomography, which images eye tissues based on light reflections; and adaptive optics, which minimizes distortion and allows higher-resolution images. I believe that these trends mark the beginning of an imaging revolution that will provide clinicians with unprecedented insight into a number of eye diseases.