Researchers have made a breakthrough that could lead to a less expensive light source for swept-source optical coherence tomography (OCT), paving the way for OCT systems that are practical for use outside the ophthalmology clinic – or even at home.
Research team member Milana Kendris from the Medical University of Vienna in Austria said the “price of laser sources and the complexity of OCT systems hinder its accessibility outside of clinics and hospitals, in particular for home care or point-of-care use”.
But she said the research team found that a vertical cavity surface emitting laser (VCSEL) diode – commonly used in telecommunications and light detection and ranging (lidar) applications – could offer a cheaper alternative.
Although other groups have demonstrated that VCSELs can be used for OCT, those systems were not designed for eye imaging.
It could also allow home-based treatment monitoring for patients with age-related macular degeneration or… diabetes
Full Eye Scans
Single-mode VSCELs usually operate using a constant current, however the researchers varied the current to achieve the changes in the wavelength, or colour, needed for swept source OCT.
In the Optics Letters journal,1 the researchers describe their custom OCT setup that incorporates a VCSEL and advanced post-processing algorithms. They used the setup to obtain full eye scans on a healthy volunteer.
In a news release,2 Ms Kendrisic said the group wanted to “develop a low-cost OCT device that could be used in a general practitioner’s office, a pharmacy or even a supermarket to allow eye check-ups without going to the ophthalmologist”.
“It could also allow home-based treatment monitoring for patients with age-related macular degeneration or… diabetes patients to monitor treatment or catch abnormal changes early, avoiding loss of vision and ultimately preserving quality of life.”
Low Cost Alternative
Swept source OCT is a relatively new OCT approach that became clinically available for eye imaging in 2010. It enables high-quality visualisation of multiple parts of the eye, but the technology is very expensive.
Because the eye is mostly filled with water, the researchers used a VCSEL that operates at 850 nm, a wavelength that isn’t absorbed strongly by water. This allows the laser light to travel through the eye to the retina and back to the detector without losing the signal to absorption.
“Even though commercial swept sources have larger spectral bandwidths, we showed that even the small range we achieved with a VCSEL is sufficient to perform OCT,” Ms Kendrisic said.
“These laser diodes could cost as little as a few dollars each… and also allow large distance ranging, which is needed for covering the full length of the human eye from cornea to retina.”
“Although VSCEL-based systems have some limitations in terms of image quality, they still have the potential to expand access to diagnostic imaging and improve patient care in areas where traditional OCT systems may not be available or affordable,” Ms Kendrisic said.
References
- Kendrisic, M., Agafonov, V., Salas, M., et al., Thermally-tuned VCSEL at 850 nm as a low-cost source alternative for full eye SS-OCT,” Opt. Lett., 48, 11, 3079-3082 (2023). DOI:org/10.1364/OL.489050.
- Optica, Technology advance lays groundwork for OCT eye imaging at home, news release, 1 June 2023, available at org/en-us/about/newsroom/news_releases/2023/june/technology_advance_lays_groundwork_for_oct_eye_ima/ [accessed 6 June 2023].
