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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.

The localized application of the riboflavin/UV-A collagen cross-linking (UV-CXL) corneal treatment has been proposed to concentrate the stiffening process only in the compromised regions of the cornea by limiting the epithelium removal and irradiation area. However, current clinical screening devices dedicated to measuring corneal biomechanics cannot provide maps nor spatial-dependent changes of elasticity in corneas when treated locally with UV-CXL. In this study, we leverage our previously reported confocal air-coupled ultrasonic optical coherence elastography (ACUS-OCE) probe to study local changes of corneal elasticity in three cases: untreated, half-CXL-treated, and full-CXL-treated in vivo rabbit corneas (n = 8). We found a significant increase of the shear modulus in the half-treated (>450%) and full-treated (>650%) corneal regions when compared to the non-treated cases. Therefore, the ACUS-OCE technology possesses a great potential in detecting spatially-dependent mechanical properties of the cornea at multiple meridians and generating elastography maps that are clinically relevant for patient-specific treatment planning and monitoring of UV-CXL procedures.

SIGNIFICANCE A novel imaging technology, dynamic optical coherence elastography (OCE), was adapted for clinical noninvasive measurements of corneal biomechanics. PURPOSE Determining corneal biomechanical properties is a long-standing challenge. Elasticity imaging methods have recently been developed and applied for clinical evaluation of soft tissues in cancer detection, atherosclerotic plaque evaluation, surgical guidance, and more. Here, we describe the use of dynamic OCE to characterize mechanical wave propagation in the human cornea in vivo, thus providing a method for clinical determination of corneal biomechanical properties. METHODS High-resolution phase-sensitive optical coherence tomography imaging was combined with microliter air-pulse tissue stimulation to perform dynamic elasticity measurements in 18 eyes of nine participants. Low-pressure (0.1 mmHg), spatiotemporally discreet (150 μm, 800 μs) tissue stimulation produced submicron-scale tissue deformations that were measured at multiple positions over a 1-mm2 area. Surface wave velocity was measured and used to determine tissue stiffness. Elastic wave propagation velocity was measured and evaluated as a function of IOP and central corneal thickness. RESULTS Submicron corneal surface displacement amplitude (range, 0.005 to 0.5 μm) responses were measured with high sensitivity (0.24 nm). Corneal elastic wave velocity ranged from 2.4 to 4.2 m/s (mean, 3.5; 95% confidence interval, 3.2 to 3.8 m/s) and was correlated with central corneal thickness (r = 0.64, P < .001) and IOP (r = 0.52, P = .02). CONCLUSIONS Phase-sensitive optical coherence tomography imaging combined with microliter air-pulse mechanical tissue stimulation has sufficient detection sensitivity to observe submicron elastic wave propagation in corneal tissue. These measurements enable in vivo corneal stiffness determinations that will be further studied for use with disease detection and for monitoring clinical interventions.

Both consumers and eye care practitioners need to know how well online optical vendors conform with the accepted standards for quality and safety. We found that almost 1 in 10 prescriptions failed to meet national standards, which is a significant improvement over previous studies.The purpose of this study was to assess the accuracy and repeatability of spectacle lens prescriptions ordered from a sample of online vendors.Spectacle lens prescriptions were ordered by paid participants with no optical training who were masked to the study objectives. The prescription powers ordered (sphere, cylinder, and axis) were statistically sampled from 1000 previously filled prescriptions. A total of 100 orders were placed with each of three online vendors that included a range of high- and low-powered single vision lenses and progressive addition lenses, and duplicate orders to assess repeatability. An independent certified testing laboratory was contracted to assess conformance with voluntary consensus standards (ANSI Z80.1-2015) and Food and Drug Administration drop-ball safety testing. Lenses not meeting these standards were counted as failures.The overall failure rates for the three vendors were 11.2 ± 3.2% (vendor A), 8.0 ± 2.7% (vendor B), and 8.2 ± 2.8% (vendor C). The repeatability for 20 prescriptions ordered five times from each vendor was high, with correlation coefficients greater than 90%. There were no observed lens impact failures.Almost 1 in 10 spectacle lens prescriptions ordered from three online vendors failed to meet national standards for optical quality. Additional studies are needed to assess eyewear ordered online for other important patient-specific variables that can influence visual performance and ultimate acceptability of prescription eyewear, such as lens placement relative to the visual axis, frame fit, and cosmetic acceptability.

Supplemental digital content is available in the text., SIGNIFICANCE Patients with glaucoma and providers recognized perceived treatment efficacy, patient-provider relationship, psychological stress, instillation skill, good quality of life, and forgetfulness as key determinants of glaucoma adherence. This shared insight could help shape the development of clinical and behavioral interventions for addressing treatment barriers and improving adherence. PURPOSE Despite their impact on adherence in glaucoma, sociobehavioral factors may not be adequately explored during clinical consultations. We aimed to elicit consensus between patients and providers around key determinants of adherence and hypothesized that patients would place greater emphasis on sociobehavioral factors compared with providers. METHODS A two-round Delphi survey was used to assess treatment beliefs, barriers, facilitators, motivators, and needs among 18 patients with glaucoma and providers. In round 1, agreement with 46 statements was scored on a 5-point Likert scale (strongly disagree to strongly agree). Statements with which 80% or more of panelists agreed reached consensus and advanced to round 2, where participants were asked to prioritize them based on their importance to treatment. RESULTS There was consensus regarding the influence of perceived treatment efficacy, good provider relationship, good quality of life, psychological stress, glaucoma knowledge, instillation skill, and forgetfulness on glaucoma adherence. For statements that failed to reach consensus, the Bonferroni-corrected Mann-Whitney U test revealed that the greatest differences between patients and providers pertained to regimen complexity (provider median, 4 [interquartile range {IQR}, 1]; patient median, 1.5 [IQR, 1]; P = .002), instillation skill (providers, 4 [IQR, 0.5]; patients, 2 [IQR, 1]; P = .001), and low motivation (providers, 3 [IQR, 2.25]; patients, 1 [IQR, 0]; P = .003). CONCLUSIONS Although patients and providers prioritized sociobehavioral factors as key determinants of adherence, disagreement between these groups was observed in other areas. Continued juxtaposition of patient and provider perspectives could spotlight underexplored areas and guide the development of successful interventions for improving adherence.

In this study, we propose to measure the spatial deformation spreading (SDS) produced by an air-pulse on the surface of tissues during the near-field regime of propagation as a metric to characterize degree of anisotropy. Experiments in isotropic tissue-mimicking phantoms and anisotropic chicken tibialis muscle were conducted using an optical coherence tomography system synchronized with a confocal air-pulse stimulation. SDS ratio measured along versus across the direction of fibers in chicken muscle agreed with the wave speed ratio taken at the same directions, demonstrating the capabilities of the air-pulse SDS technique in measuring the elastic anisotropy of transverse isotropic tissues.

We have designed and developed an air-coupled ultrasonic radiation force probe co-focused with a phase-sensitive optical coherence tomography system (ACUS-OCT). Our custom-made 1 MHz spherically focused piezo-electric transducer with a concentric circular opening of 10 mm diameter allows for the confocal micro-excitation of waves and the spatial (2D, 3D) motion measurement of tissues. Phantom studies demonstrated the capabilities of this probe to produce quasi-harmonic excitation up to 4 kHz for the generation of highly localized elastic waves. Experimental results in ocular tissues showed the highly localized 2D/3D elasticity mapping capabilities of this approach with great potential for clinical translation.

The purpose of this study is to evaluate the changes in elasticity of the corneo-scleral limbus when the eye-globe is subjected to different intraocular pressures. Continuous elastic waves were mechanically induced in the sclera and imaged using a phase-sensitive optical coherence tomography system. Experimental results showed a marked heterogeneity of wave speed across the corneal-limbal-scleral region, which increased as a function of IOP. The conclusion of this study reveals that the corneo-scleral limbus tissue is more mechanically nonlinear compared to the cornea and sclera. This suggests that limbus acts as a supporting and accommodating mechanical structure for the cornea.

In optical coherence elastography (OCE), air-pulse stimulation has been widely used to produce propagation of mechanical waves for elastic characterization of tissues. In this paper, we propose the use of spatial deformation spreading (SDS) on the surface of samples produced by air-pulse stimulation for the OCE of transverse isotropic tissues. Experiments in isotropic tissue-mimicking phantoms and anisotropic chicken tibialis muscle were conducted using a spectral-domain optical coherence tomography system synchronized with a confocal air-pulse stimulation. SDS measurements were compared with wave speeds values calculated at different propagation angles. We found an approximately linear relationship between shear wave speed and SDS in isotropic phantoms, which was confirmed with predictions made by the numerical integration of a wave propagation model. Experimental measurements in chicken muscle show a good agreement between SDS and surface wave speed taken along and across the axis of symmetry of the tissues, also called degree of anisotropy. In summary, these results demonstrated the capabilities of SDS produced by the air-pulse technique in measuring the shear elastic anisotropy of transverse isotropic tissues.

Purpose Currently, the biomechanical properties of the corneo-scleral limbus when the eye-globe deforms are largely unknown. The purpose of this study is to evaluate changes in elasticity of the cornea, sclera, and limbus when subjected to different intraocular pressures (IOP) using wave-based optical coherence elastography (OCE). Special attention was given to the elasticity changes of the limbal region with respect to the elasticity variations in the neighboring corneal and scleral regions. Methods Continuous harmonic elastic waves (800 Hz) were mechanically induced in the sclera near the corneo-sclera limbus of in situ porcine eye-globes (n = 8). Wave propagation was imaged using a phase-sensitive optical coherence tomography system (PhS-OCT). The eyes were subjected to five different IOP-levels (10, 15, 20, 30, and 40 mm Hg), and spatially distributed propagation velocities were calculated along corneal, limbal, and scleral regions. Finite element analysis (FEA) of the same regions under the same excitation conditions were conducted for further validation of results. Results FEA demonstrated that the stiffness of the heterogeneous cornea-limbus-sclera transition can be characterized by phase velocity measurements of the elastic waves produced at 800 Hz in the anterior eye. Experimental results revealed that the wave speed in the limbus (cL = 6.5 m/s) is between the cornea (cc = 2.9 m/s) and sclera (cs = 10.0 m/s) at a physiological IOP level (15 mm Hg) and rapidly increases as the IOP level is increased, even surpassing the wave speed in the sclera. Finally, the change in elastic wave speed in the limbus (ΔcL∼18.5 m/s) was greater than in the cornea (Δcc ∼12.6 m/s) and sclera (Δcs∼8.1 m/s) for the same change in IOP. Conclusions We demonstrated that wave-based OCE can be utilized to assess limbus biomechanical properties. Moreover, experimental evidence showed that the corneo-scleral limbus is highly nonlinear compared to the cornea and sclera when the eye-globe is deformed by an increase of IOP. This may suggest that the limbus has enough structural flexibility to stabilize anterior eye shape during IOP changes.