New imaging technology may help diagnose neurological conditions

Researchers in Canada refine targeted ocular spectroscopy for the eyes

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by Andrea Lobo |

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Targeted ocular spectroscopy, a technology that allows real-time imaging of the back of the eye (or eye fundus) while observing how light interacts with specific structures in the retina, can help diagnose several eye and neurological conditions, including Parkinson’s disease, according to a recent study.

The retina is the light-sensitive layer at the back of the eye. It plays a crucial role in converting incoming light into electrical signals, which then are transmitted through the optic nerve to the brain.

The study “Targeted spectroscopy in the eye fundus,” was published in the Journal of Biomedical Optics.

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The assessment of biomarkers in the eye can be used to help screen, diagnose, and monitor diseases affecting the eyes, as well as neurological conditions, including Parkinson’s and Alzheimer’s disease. These conditions were shown recently to cause observable changes in the nerves and blood flow of the retina.

Eye care professionals generally rely on color imaging and computed tomography, which captures images within the body using X-rays, to diagnose ocular diseases. Spectroscopy techniques allow the study of how light interacts with tissues by splitting the light into a spectrum of colors,  providing diagnostic information complementary to standard eye-imaging methods.

However, currently used spectroscopy methods have several limitations, such as the inability to detect fine spectral changes in localized retinal structures, or requiring the fixation of patients, “which can be laborious when fine positioning is required,” the researchers wrote.

To address these issues, a research team at the University of Alberta, in Canada, developed a flexible and versatile system for targeted spectroscopy in the eye.

How the new imaging technology works

The device includes illumination LEDs, a color camera and a spectrometer, which can be used simultaneously for real-time color imaging and spectral measurements.

The device’s spectrometer also focuses a LED in a small region of the retina, and the position of the region of interest can be adjusted through simple mechanisms that rotate the beam splitter that feeds the camera and the spectrometer.

This makes it easier to perform spectral measurements in specific eye structures, such as the optic nerve and retina, as well as to identify blood leakage, fat deposits, or other lesions. It also can be used to measure fluorescence, which extends its applicability to a wider variety of biomarkers.

“The user can select a target and move it to any location within the eye fundus region being imaged … while continuously receiving spectral information of the targeted sampled area,” researchers wrote.

In the study, researchers demonstrated the system functionality using both lab models and retina measurements in healthy volunteers. First, they confirmed the system’s ability to acquire a spectrum from a specific target region, using colored areas in a reference target with a grid-like pattern.

Then, using an eye model, the system was able to effectively measure distinct spectral signatures for different eye regions — namely blood vessels, the retina near the optic nerve head, the optic nerve head, and the retina far from the optic nerve head. While only small changes were detected between the two regions of the retina, clear differences were observed between blood vessels and the optic nerve.

Moreover, measurements performed on the retinas of eight healthy individuals showed different spectral profiles of the optic nerve and a region of the retina called the parafovea. Based on targeted spectral analysis, researchers also were able to assess oxygen levels in different locations of the eye fundus.

Overall, the new technology “provides structural, compositional, and functional information of specific regions of the eye fundus from a non-invasive approach to ocular biomarker detection,” the researchers wrote.

‘An increasingly important tool’

“Targeted ocular spectroscopy has the potential to assess the presence of … hemoglobin [the protein that transports oxygen throughout the body], oxyhemoglobin [the oxygen-bound hemoglobin], melanin [a substance that produces skin, hair, and eye color], or lipofuscin [an ‘aging’ pigment that accumulates progressively in cells], associated with disease progression,” the researchers wrote.

“This could open the door to change the way we diagnose and treat eye diseases, and targeted ocular spectroscopy could become an increasingly important tool in eye care in the coming years,” they concluded.