New Technique Captures Nine Corneal Points Simultaneously

Researchers at the International Centre for Translational Eye Research (ICTER) have built a prototype optical coherence tomography (OCT) system that maps how the cornea deforms after a brief air puff at nine different locations during a single measurement. The approach aims to overcome a key limitation of conventional biomechanics testing: most methods sample the corneal response sequentially or in only one plane, which can distort results when the tissue’s mechanical reaction is fast and non-repeatable.

The cornea is not only a transparent focusing surface but also a mechanically active tissue. Its stiffness and deformation behavior influence vision quality and can change early in disorders such as keratoconus, sometimes before standard imaging reveals obvious structural damage. Detecting those early mechanical signatures could improve diagnosis, risk assessment, and monitoring of treatment outcomes.

The study—published in Biomedical Optics Express—introduces a “single-shot, depth-encoded multiplexed OCT” design. Instead of probing the cornea with one beam at a time, the system sends multiple beams that strike the cornea simultaneously at a central point and eight peripheral positions. The signals are separated using depth encoding, allowing the corneal dynamics at all nine sites to be recorded within one acquisition.

This simultaneous strategy is crucial because the corneal response to the air stimulus lasts only about 20 milliseconds. Conventional scanning can introduce temporal mismatch between locations, especially when eye motion, blinking, or tear-film fluctuations occur during the measurement. By freezing the event in time, the prototype aims to produce a more faithful biomechanical map.

To characterize accuracy, the researchers varied temporal sampling. When sampling was degraded from 10 microseconds to 250 microseconds, asymmetry magnitude errors rose to roughly 20%, and at 1 millisecond errors approached 70%. Direction estimates were also sensitive, with angular errors increasing sharply as temporal resolution worsened.

From the multi-point deformation data, the team derived an “asymmetry vector” that summarizes local imbalance: its magnitude indicates how strong the difference is between center and peripheral regions, while its direction points toward where deformation is greatest. In keratoconus patients, the vector direction consistently aligned with regions showing thinning, steeper curvature, and abnormal posterior elevation.

Interestingly, validation experiments revealed a previously unreported “dual-indentation response,” where the cornea can exhibit two distinct deformation phases after a single air pulse. The effect emerged after modifying the air nozzle diameter, changing how force distributes across the corneal surface—highlighting the value of simultaneous, ultrafast observation.

While the work is primarily a proof of concept, the researchers see clear potential for earlier keratoconus detection, longitudinal monitoring, and improved decision-making for procedures such as cross-linking and refractive surgery planning. Future versions will require automated OCT segmentation and robust eye-alignment features to make the system practical in clinics.

Keywords

OCT, corneal biomechanics, keratoconus, air-puff testing, multi-spot imaging, depth-encoded multiplexing, asymmetry vector, single-shot acquisition, optical coherence tomography