Corneal stiffness plays a critical role in shaping the cornea with respect to intraocular pressure and physical interventions. However, it remains difficult to measure the mechanical properties noninvasively. Here, we report the first measurement of shear modulus in human corneas in vivo using optical coherence elastography (OCE) based on surface elastic waves. In a pilot study of 12 healthy subjects aged between 25 and 67, the Rayleigh-wave speed was 7.86 ± 0.75 m/s, corresponding to a shear modulus of 72 ± 14 kPa. Our data reveal two unexpected trends: no correlation was found between the wave speed and IOP between 13–18 mmHg, and shear modulus decreases with age (− 0.32 ± 0.17 m/s per decade). We propose that shear stiffness is governed by the interfibrillar matrix, whereas tensile strength is dominated by collagen fibrils. Rayleigh-wave OCE may prove useful for clinical diagnosis, refractive surgeries, and treatment monitoring.

Optical fibers made of thermoset elastomeric materials can offer extremely high stretchability not possible with conventional glass and plastic optical fibers. However, such elastomer fibers have so far been made with large mm‐scale diameters, which limit their potential utilities. Here, fabrication of small‐diameter (< 200 µm), core‐clad optical fibers using a thermal drawing of transparent thermoplastic elastomers is demonstrated. The single‐mode optical fibers fabricated by this method are highly elastic and durable against strain up to 700%. Furthermore, a composite thermoplastic‐thermoset elastic optical fiber is also presented, in which the advantageous properties of both families of elastomers are combined. These optical fibers may be useful for short‐distance, mechanically flexible, optical interconnections in biomedical, wearable, or implantable photonic devices.

Purpose-To investigate the feasibility of using Brillouin microscopy for assessment of corneal edema in patients with Fuchs' Endothelial Corneal Dystrophy (FECD). Brillouin microscopy analyzes the frequency shift of light inelastically scattered by naturally occurring acoustic waves in a small volume of tissue. The resulting frequency shift is a measure of the local hydromechanical properties of the tissue.Methods-Participants were scanned using a clinical Brillouin imaging system (780 nm laser, 5 mW) and a color-coded map of the mean Brillouin shift laterally across the corneal stroma was created.Results-Brillouin maps of normal subjects (n = 8) were relatively homogeneous, while FECD patients' (n = 7) maps exhibited significantly reduced Brillouin shifts (unpaired t test, P < .001) centrally. The mean difference of 83 MHz corresponds to approximately 3.9% higher water content (percentage difference in volume fraction) in central corneas of FECD group relative to normal subjects. The Brillouin scan of a FECD patient 1-month after Descemet membrane endothelial keratoplasty (DMEK) measured a 62 MHz increase in Brillouin shift relative to preoperative level, indicating normalization of corneal hydration.Conclusions-All FECD patients scanned exhibited a centralized reduction in Brillouin shift, distinct from the normal subjects measured, and consistent with centralized edema characterized by pachymetry. Brillouin scans revealed substantially reduced water content after DMEK. These results suggest that Brillouin microscopy could aid treatment planning and assessment of FECD. Moreover, corneal hydration mapping may be useful in understanding fluid pump function dynamics of the cornea and developing early interventions for FECD.