No abstract

Assessing corneal biomechanics in vivo has long been a challenge in the field of ophthalmology. Despite recent advances in optical coherence tomography (OCT)-based elastography (OCE) methods, controversy remains regarding the effect of intraocular pressure (IOP) on mechanical wave propagation speed in the cornea. This could be attributed to the complexity of corneal biomechanics and the difficulties associated with conducting in vivo corneal shear-wave OCE measurements. We constructed a simplified artificial eye model with a silicone cornea and controllable IOPs and performed surface wave OCE measurements in radial directions (54–324°) of the silicone cornea at different IOP levels (10–40 mmHg). The results demonstrated increases in wave propagation speeds (mean ± STD) from 6.55 ± 0.09 m/s (10 mmHg) to 9.82 ± 0.19 m/s (40 mmHg), leading to an estimate of Young’s modulus, which increased from 145.23 ± 4.43 kPa to 326.44 ± 13.30 kPa. Our implementation of an artificial eye model highlighted that the impact of IOP on Young’s modulus (ΔE = 165.59 kPa, IOP: 10–40 mmHg) was more significant than the effect of stretching of the silicone cornea (ΔE = 15.79 kPa, relative elongation: 0.98–6.49%). Our study sheds light on the potential advantages of using an artificial eye model to represent the response of the human cornea during OCE measurement and provides valuable insights into the impact of IOP on wave-based OCE measurement for future in vivo corneal biomechanics studies.

Assessing corneal biomechanics in vivo has long been a challenge in the field of ophthalmology. Although recent wave-based optical coherence elastography (OCE) methods have shown promise in this area, the effect of intraocular pressure (IOP) on mechanical wave propagation in the cornea remains unclear. To address this, we constructed an artificial eye model and performed surface wave OCE measurements in the radial directions (54–324°) of the silicone cornea at varying IOP levels (10–40 mmHg). The results demonstrated increases in wave propagation speeds (mean ± STD) from 6.55 ± 0.09 m/s (10 mmHg) to 9.82 ± 0.19 m/s (40 mmHg), leading to an estimate of Young’s modulus, which increased exponentially from 145.23 ± 4.43 kPa to 326.44 ± 13.30 kPa. Our implementation of an artificial eye model highlighted that the impact of IOP on Young’s modulus (ΔE = 165.59 kPa, IOP: 10–40 mmHg) was more significant than the effect of stretching of the silicone cornea (ΔE = 15.79 kPa, relative elongation: 0.98%–6.49%). Our study sheds light on the potential of using an artificial eye model in OCE research for corneal biomechanics. Furthermore, it is critical to consider the impact of IOP on measurement results when utilizing wave-based OCE in clinical settings for enhanced assessment of corneal biomechanics.

Microliter air-pulse stimulated optical coherence elastography (OCE) was recently proposed for tissue biomechanical characterization using natural frequency oscillations. However, previous studies have not quantified actual stimulation parameters (e.g. time-frequency analysis), obscuring the actual stimulation-response function, leading to potential errors in natural frequency measurement. We propose a dual-channel air-pulse OCE method with one channel stimulating the sample and the other simultaneously measured with a pressure sensor. While pressure amplitude differences were ~10%, the frequency profiles were identical (duration: 3–35 ms; pressure: 20 Pa to 2 kPa) for both channels. The frequency response function was used to characterize the resonant features of agar phantoms (concentrations: 1–2%) and a silicone cornea phantom in an artificial anterior chamber eye model (intraocular pressure, IOP: 5–40 mmHg) under a 200 Pa stimulation pressure. The measured dominant natural frequencies increased with agar concentrations (181 Hz to 359 Hz, maximum displacements: 0.14–0.47 µm) and IOPs for the silicone cornea (333 Hz to 412 Hz, maximum displacements: 0.41–0.52 µm). These frequencies were consistent across different air–pulse durations, though coefficient variation increased as stimulus duration increased. The dual-channel OCE approach, using low-pressure stimulation and small-amplitude oscillation features, can advance our understanding of sample frequency responses when accessing delicate tissues, such as the human cornea in vivo.

Microliter air-pulse stimulated optical coherence elastography (OCE) was recently proposed for tissue biomechanical characterization using natural frequency oscillations. However, previous studies have not quantified actual stimulation parameters (e.g. time-frequency analysis), obscuring the actual stimulation-response function, leading to potential errors in natural frequency measurement. We propose a dual-channel air-pulse OCE method with one channel stimulating the sample and the other simultaneously measured with a pressure sensor. While pressure amplitude differences were ~10%, the frequency profiles were identical (duration: 3–35 ms; pressure: 20 Pa to 2 kPa) for both channels. The frequency response function was used to characterize the resonant features of agar phantoms (concentrations: 1–2%) and a silicone cornea phantom in an artificial anterior chamber eye model (intraocular pressure, IOP: 5–40 mmHg) under a 200 Pa stimulation pressure. The measured dominant natural frequencies increased with agar concentrations (181 Hz to 359 Hz, maximum displacements: 0.14–0.47 µm) and IOPs for the silicone cornea (333 Hz to 412 Hz, maximum displacements: 0.41–0.52 µm). These frequencies were consistent across different air–pulse durations, though coefficient variation increased as stimulus duration increased. The dual-channel OCE approach, using low-pressure stimulation and small-amplitude oscillation features, can advance our understanding of sample frequency responses when accessing delicate tissues, such as the human cornea in vivo.