Innovative Hand-Held OCT Probe Takes High-resolution Images of Children’s Retinas
Researchers and ophthalmologists from Duke University have presented a new option to examine children’s eyes in a new study entitled “In vivo cellular-resolution retinal imaging in infants and children using an ultracompact handheld probe” published in Nature Photonics.
The new handheld device is about the same size as a pack of cigarettes, weighs next to nothing and is capable of gathering detailed information about the retina’s cellular structure.
The device is being hailed as a great achievement as up to now it has been very difficult to gather data as to how a child’s retina develops, as it matures by the age of 10. This has severely impacted and limited knowledge of how diseases affect a child’s vision early in life and has made diagnosing various diseases more difficult.
The human eye presents an extraordinary opportunity for research and imaging because it is easy to access; it is relatively self-contained; improvements in function can be easily measured, and there is even a natural opening that allows us to peer inside. The eye is also delicate though, with complex vital structures concealed mere millimetres below various surfaces, which necessitates the use of a wide range of technologies to study it.
There have been many tools and technologies designed to study the eye over the past few decades, the most popular of these being Optical Coherence Tomography (OCT), which works by shining specific frequencies of light into the tissues of the eye and comparing the reflections to identical but unimpeded light waves, allowing researchers to build 3-D images of the back of the eye that are several millimetres deep .
The problem with the equipment so far though has been that it has been bulky, big, heavy and time-consuming, which is never a good idea with toddlers.
Cynthia Toth, Professor of Ophthalmology and Biomedical Engineering at Duke University said:
“Diagnostic tools that examine and image the retina have been well-designed for adults, but are exceedingly difficult to use in infants and young children who can’t hold the required position or focus for long enough periods of time. Before now, it hasn’t been possible to measure the impact of injury or diseases on their photoreceptors, the cells in the eye in which light is first converted into nerve signals.”
This is great news as it could shed a lot of light on hereditary paediatric retinoblastoma, which is the most common intraocular cancer found in children. Retinoblastoma was the first cancer to be directly associated with a genetic abnormality, and it can occur sporadically or it can be inherited.
Retinoblastoma occurs in 1 in 18,000 to 30,000 live births worldwide. and it has been the subject of great interest because of its well-studied genetic inheritance pattern and molecular biology.
A new type of smaller scanning mirror recently reached a point where it could replace larger, older models. A new design using converging rather than collimated light cut the telescoping length of the device by a third.
Custom lenses detailing curvature, thickness and glass type were designed by first author Francesco LaRocca and specially fabricated.
A mechanical design to hold and integrate the components was designed by Derek Nankivil — who, like LaRocca, recently graduated with a PhD from Duke — and fabricated in a machine shop on Duke’s campus.
The new device was then given to clinicians for testing on adults, which proved that it was capable of getting accurate photo-receptor density information. It was also used for research imaging in children who were already having an eye exam under anaesthesia.
According to the developers, it …”was able to quantify packing densities of parafoveal cone photo-receptors and visualize cross-sectional photo-receptor substructure in children ranging from 14 months to 12 years.”
The new hand-held probe is based on OCT and other technologies, features a compact optical design weighing a mere 94 grams. It allows researchers to gather structural information about the eyes of infants and toddlers for the first time.
“But because children have never been imaged with these systems before, there’s no gold standard that we can compare it to,” said LaRocca. “The results do, however, match theories of how cones migrate as the eye matures.
The tests also showed different microscopic pathological structures that are not normally possible to see with current lower-resolution clinical-grade handheld systems.”
The prototype is being used by clinicians at Duke Health, which means that the amount of information being gained from children’s scans could eventually create a database to give a much better picture of how the retina matures with age.
Joseph Izatt, the Michael J. Fitzpatrick Professor of Engineering at Duke and a pioneer of OCT technology said:
“This paper demonstrates the first time researchers have been able to directly measure the density of photoreceptors called cones in infants. As such, it opens the door to new research that will be key in future diagnosis and care of hereditary diseases.”
The group is already working on the next generation of the design after getting feedback from clinicians on what can be improved.