Investigative Ophthalmology & Visual Science
RPE cell mosaics (top) and
mapping, mosaics (bottom) at
on the retina of a
In-Vivo Images of Retina’s
Retinal pigment epithelial (RPE) cells
play a vital role in maintaining the
health of the human retina, especially
its photoreceptors (rods and cones).
However, until recently, physicians had
di culty seeing individual RPE cells
to assess them for potentially eyesight-robbing abnormalities.
A team at the University of Rochester (N.Y., U.S.A.) has taken the first
images of this layer of so-called “dark
cells” in a living retina (Invest. Oph-thalmol. Visual Sci. 50, 1350). e
imaging technique, which involves
adaptive optics and autofluorescence,
could someday help doctors catch certain eye diseases in their early stages.
A single layer of RPE cells, which
are nearly black, recharges the rods and
cones with pigment molecules after
exposure to light and collects the toxic
waste products from the photoreceptors.
Despite their darkness and their position
behind the light receptors, physicians
will need to study living RPE tissues
to assess the e cacy of any future drug
treatments for eye diseases.
In 1997, David R. Williams, a
professor of optics, and his Rochester
colleagues developed an adaptive optics
camera with a Hartmann-Shack wavefront sensor and a 37-actuator mirror to
image photoreceptors in vivo. In 2007, a
University of California group used an
adaptive optics system combined with
a scanning laser ophthalmoscope to
obtain reflectance images of living RPE
cells in regions of the retina where cones
were missing. However, that technique
did not work in healthy retinas because
of interference with the signal from the
Fortunately, in the course of performing their duties, RPE cells accumulate
a pigment called lipofuscin, which is
made up of autofluorescence molecules.
Williams’ team leveraged the autofluorescence along with the adaptive optics
scanning laser ophthalmoscope and
simultaneous dual-wavelength imaging
e experimental setup scanned
the retina with three lasers: a 568-nm
argon-krypton tunable laser to stimulate
autofluorescence, an 830- or 794-nm
diode laser for reflectance imaging, and
a 904-nm diode laser for wavefront sensing. Although the RPE cells fluoresce
only dimly, the adaptive optics teases out
the glow from the individual cells.
e ability to see individual RPE
cells could help scientists learn how they
contribute to macular degeneration and
other retinal diseases. If doctors could
catch these diseases in their early stages,
prompt treatment could save eyesight.
Patricia Daukantas ( email@example.com) is the senior writer/editor of Optics & Photonics News.
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