Handheld probe images
photoreceptors in children
August 27, 2018
University researchers have developed a handheld probe that can image
individual photoreceptors in the eyes of infants.
The technology, based on adaptive optics, will make it easier for
physicians and scientists to observe these cells to diagnosis eye
diseases and make early detection of brain-related diseases and trauma.
Photoreceptors are specialized neurons that comprise the light-sensing
cells of the retina, an extension of the central nervous system located
at the back of the eye. The retina sends signals to the brain via the
optic nerve, which then processes the visual information. Previous
studies have shown that neurodegenerative diseases, including
Alzheimer's and Parkinson's, as well as traumatic brain injuries, such
as concussions, can alter the neuronal structures in the retina.
A new hand-held
ophthalmology instrument allows imaging of photoreceptors in the eyes of
young children. It could help to improve the diagnosis of eye diseases
and eventually find use in early detection of brain-related diseases and
To study these neuronal
structures, researchers commonly use an adaptive optics scanning laser
ophthalmoscope (AOSLO), a non-invasive tool that provides a
significantly higher image resolution than an MRI.
Although traditional AOSLO allows researchers to visualize individual
photoreceptor cells, such systems are as large as a billiard table,
costly and extremely complex. Its use has been limited to patients who
are able to sit upright fix their gaze for several minutes, which means
it is not as useful for young children or for adults with cognitive or
The new system, called HAOSLO for handheld AOSLO, measures just 4 inches
by 2 inches by 5.5 inches, and weighs less than half a pound.
The Duke researchers transformed the AOSLO into a handheld probe by
improving its optical, signal processing and mechanical designs. This
included development of a new algorithm that replaces the traditional
AOSLO's large wavefront sensing system, an optical component that can
detect light distortion caused by the eye.
The study appears August 23 in the journal Optica.
"Other researchers have shown that the wavefront sensor can be replaced
by an algorithm, but previous algorithms haven't been fast or robust
enough to be used in a handheld device," said Theodore DuBose, a PhD
student in the department of biomedical engineering at Duke and the
first author of the paper. "The algorithm we developed is much faster
than previous techniques and just as accurate."
The tool was tested in a clinical trial with 12 adults and two children,
where the team demonstrated its ability to capture detailed images of
photoreceptors close to the fovea--the center of the retina where
photoreceptors are smallest and vision is most acute.
"Our new tool is fast and lightweight so physicians can take it directly
to their patients, and the probe allows us to collect images quickly,
even if there is movement," said Sina Farsiu, an associate professor in
the departments of biomedical engineering and ophthalmology. "These
capabilities allow us to open up the pool of patients who could benefit
from this technology."
tool's new design makes it especially useful for imaging the eyes of
young children. For example, premature newborns have a greater risk of
developing eye diseases, like retinopathy, which can lead to blindness
if not diagnosed quickly. Researchers can also use the tool to track
early brain development in children by imaging their retina, which
develops along with the central nervous system.
The team is optimistic about the tool's use both inside and outside of
the hospital. Because the HAOSLO can be taken into an operating room,
physicians will be able to see the photoreceptors at the highest
resolution possible during surgery, even when a patient is under
anesthesia and in a reclined position. It could also help doctors
rapidly assess possible brain trauma in athletes, such as football
players coming off the field with head injuries.
Before the researchers prepare for large-scale clinical trials, they
plan to incorporate additional imaging modes for detecting other
They also have made the mechanical designs, computational algorithms and
control software freely available online so that other scientists can
adapt the new system for their scientific applications.