PICO device set to aid corneal ulcer diagnosis

15 Mar 2022

University of Arizona project supported by $1 million from National Eye Institute.

DK Kang: small-scale optical platforms

Such ulcers cause visual impairment or blindness and can be common in rural farming communities, arising from scratches to the cornea suffered during field work. More than 4 million people are afflicted with the condition per year.

Since the kind of clinic-scale ophthalmology examinations that can spot the condition are impractical in the communities most affected, a smaller hand-held examination platform would be a valuable step in reducing cases.

The UArizona project aims to create a portable in vivo confocal ophthalmoscope, or PICO, and is currently funded by $1 million from the US National Eye Institute. Leading the project is Dongkyun "DK" Kang, whose previous work on confocal platforms suitable for easily diagnosing cancer in limited-resource scenarios has fed into the new project.

Current rural testing for corneal ulcers relies on visual examination using a simple slit lamp, but this cannot easily show whether the cause of the condition is fungal, parasitic or bacterial, a key distinction for treatment.

The University of Manchester's Jaya Chidambaram has been trialing the use of confocal microscopy as an alternative, and found that although results were better, the machines were inconveniently complex and the testing took too long. Contact with Kang at UArizona about the issue led to the formation of the new project.

"She came with a problem, I came with a solution, and we felt like this was a really good match," said Kang.

Adoption as a standard corneal imaging tool

Shrinking the size of confocal microscopy platforms is a constantly evolving goal of optics developers, going hand in hand with developments in optical components and MEMS scanning techniques. Kang's previous work on similarly small-scale imaging devices for cancer diagnosis was part of these efforts, aiming to develop a smartphone endoscope costing under $3,000 rather than the $50,000 price tag of full-scale platforms.

At SPIE Photonics West 2020 (pdf), Kang's work on small-scale cancer imaging was described as as an example of "where optics is going," during that year's BIOS conference.

"This is all because of advances in photonics," commented 2020 BIOS co-chair Jennifer Barton, referring to Kang's research. "You can use a small laser diode and implement it in the imaging and diagnostic devices that we are building. Today you can manufacture small optics at a reasonable price."

PICO is intended to scan in two dimensions rather than one, line by line rather than dot by dot. It will use a diffraction grating to create a scanning line so that a larger portion of the eye can be scanned at a time without sacrificing image quality. The goal is a portable device able to yield results in around two minutes, and which does not involve direct contact with the patient's cornea.

"We use that diffraction method to scan and illuminate an image in the entire area of tissues, without having to mechanically scan anything," Kang said. "This makes it possible to increase the speed by up to 20 times and reduce the cost by up to eight times. We strongly believe that PICO will be adopted as a standard corneal imaging tool, and its availability in a wide range of health care settings will fundamentally improve eye care worldwide."