Window to your soul: artificial cornea implants

3 January 2018

Dr Pui-Chuen Hui (Croucher Fellowship, 2014) has been investigating the feasibility of implanting a fibre-optic pressure sensor into an artificial cornea.

Dr Pui-Chuen Hui (Croucher Fellowship, 2014) is a Research Fellow at the Massachusetts Eye and Ear Infirmary (MEEI). He has been investigating the feasibility of implanting a fibre-optic pressure sensor into an artificial cornea, to accurately measure intraocular pressure (IOP). Hui’s technology seeks to address the unique challenge of managing glaucoma in patients with artificial cornea implants. In addition to his current work, Hui has a rich portfolio of research into photonics and optical physics, ranging from nonlinear mechanics with optical gradient and near-field forces in coupled photonic crystal structures, to novel biomedical interferometric imaging strategies, facilitated by compressive sensing and optical path length-multiplexing with multimode fibres.

Hui’s ventures in biomedicine originated from the catalytic idea of a scientist’s social responsibility. “As a young and naïve graduate student, I was fully contented with frontier photonics research. I never saw the need to branch out. However, I remember sitting in a nonlinear optics class, taught by Professor James Fujimoto at MIT, as he spent quite some time directing our attention to what society contributes to our graduate studies. Simply put, the privileges and the resources granted to scientists are largely derived from taxpayer’s money.” Hui was struck with the need to use his position to give something back.

Exchange with his neurobiologist-ophthalmologist wife further ushered Hui into exploring the synergistic opportunities between optical physics and biomedicine, as a way of giving back to society. Hui’s career progressed from studying the dynamics of optomechanical systems, to devising new optical imaging methods, and optical devices for biomedical applications. He relates, “I noticed there was a communication gap between the photonic device community and the biomedical world. Having been immersed in these two different environments, I had the opportunity to communicate the novelties and caveats of new techniques back and forth. It helped to inspire and distil realistic solutions to tackle biomedical imaging problems.”

One such solution was an optical device based approach to glaucoma management. Elevated intraocular pressure (IOP), or ocular hypertension, is linked with an increased risk of glaucoma; a disease which, according to the Glaucoma Foundation, is the world’s leading cause of blindness. It is also one of the post-operative complications that limits the long-term outcome for patients who receive the artificial cornea transplant known as the Boston Keratoprosthesis (B-KPro), pioneered by Dr Claes H. Dohlman at MEEI.

Despite its high retention rate and satisfactory post-operative visual acuity in patients, standard IOP-monitoring methods, including Goldman tonometry, or recent MEMS-based devices such as TriggerFish, are not amenable to this patient group due to the keratoprosthesis’ mechanical rigidity. Hui’s solution to this was to integrate a compact fibre-optic pressure sensor into the corneal prosthetic implant, which directly probes the IOP in the anterior chamber.

When asked about the real-world practicality of his optical, Hui explains that although the technology of fibre-optic sensors is not new, the crux of this development is how to couple light to the sensor, and extract the required information in an efficient and comfortable manner, in a fast-paced eye clinic.

Another one of Hui’s design considerations for optical sensing devices is improving their small-scale compatibility and portability. This introduces a new set of challenges. Hui’s graduate research work at the Laboratory of Nanoscale Optics at Harvard University focused on the understanding of the Casimir effect, as it relates to nanotechnology.

The Casimir force is a quantum electrodynamical force between two uncharged objects, which could be quite large when in these objects are in close proximity. The smaller the technology, the more significant the force. Hui expounds, “Advances in nanofabrication techniques allow many tiny moving functional parts to be packed into a small space. These types of forces then become significant, and even detrimental to a device. Therefore, we need to characterise these near-field forces to gain control over them… Our approach featured a chip-based platform for Casimir force characterisation. Such a platform becomes an interesting playground for theorists to study some of the novel geometrical influences in the manifestation of the Casimir effect. Interestingly, we can even use repulsive optical forces, resonantly enhanced by photonic crystals, to counteract the Casimir effect.”

The optomechanical platform and fibre-optic detection architecture for performing sensitive measurement of the Casimir effect, and optical forces, is finding its way back to Hui’s current research. With similar physical principles of sensitive displacement measurement via spectroscopic fibre-optic interferometry and insights from cavity optomechanics, Hui moved from measuring the Casimir and optical pressure in a vacuum chamber, to measuring the IOP of the anterior chamber of a patient’s eye. In the near future, he looks forward to developing a mobile IOP-monitoring system that can be used outside of the clinic.

As for the future, Hui would like to continue exploring the application of physics to other fields of study, namely, choral music. “I have always been totally captivated by the blending, tuning and breathtaking togetherness of choral music; it really is so different, so intriguing. I would love to delve into the physics of choral music within the framework of coupled oscillators and synchronization phenomena.”

Dr Pui-Chuen Hui obtained his BS in Applied and Engineering Physics from Cornell University in 2008, where he worked with Professor Farhan Rana on terahertz biomolecule detection, and with Professor Alex Gaeta on nonlinear optics. In 2012, he undertook his MS in Engineering Science at Harvard University. Hui went on to receive his PhD in Applied Physics, Electrical Engineering in 2014, after conducting research at the Laboratory of Nanoscale Optics of Professor Marko Loncar, at the School of Engineering and Applied Sciences at Harvard University. His research focused on the detection and optomechanical counteraction of the Casimir effect in an integrated MOEMS platform. He also received a Croucher Foundation Fellowship that year to perform research work in optical biomedical imaging at Professor Brett Bouma’s lab at Wellman Centre for Photomedicine, Massachusetts General Hospital. Dr Hui is also a proud alumnus of the Cornell Glee Club (07-08), Harvard Glee Club (08-10) and Tanglewood Festival Chorus.

To view Dr Hui's Croucher profile, please click here