Fig 1.
Left: OCT elastography system patient interface schematic diagram. Right: Photograph of the optical coherence elastography prototype highlighting the applanating apparatus (lens, force sensors and linear actuator stage).
Fig 2.
Example OCT elastography results for the right eye of patient one.
Top left: Frame of the point of maximum compression. Anterior (blue box) and posterior (red box) stromal regions of interest were defined to generate the force/displacement relationships on the right. Note that the corneal epithelium was intact in all eyes (visible in top left frame) and was included in all analyses except the anterior/posterior stromal region comparisons. Top right: Force vs. displacement plot depicting differences in axial stiffness approximations for the anterior and posterior stromal regions. Higher slopes are consistent with stiffer behavior. Middle Left: Cumulative displacement map of the central cornea in microns. Middle Right: Depth-dependent cumulative displacement profile along a central 100um wide band (averaged laterally) through the depth of the cornea. Bottom left: Elastography map overlaid with the corneal image of the point of maximum compression presenting local values for the slope of the force (grams) vs. displacement (μm) relationship, an approximation of axial/compressive stiffness. Cooler colors indicate higher approximate stiffness corresponding to smaller displacement magnitudes than warmer colors. Bottom right: Depth-dependent k profile, representing the approximate stiffness behavior along a central 100um-wide band (averaged laterally) through the depth of the cornea.
Table 1.
Demographic and tomographic data for each subject.
Table 2.
Approximation of axial stiffness from the slope term of the force/displacement relationship for anterior and posterior corneal stroma.
Fig 3.
Linear regression results between ka/kp (the anterior/posterior stromal response ratio) and A) the mean anterior corneal curvature and B) IOP for all eyes. Despite a trend toward lower with increasing corneal curvature, neither correlation was statistically significant. S = standard error, R-sq = coefficient of variation, CI = confidence interval, PI = prediction interval.
Fig 4.
System sensitivity to the intra-eye IOP variability.
Anterior (A), and posterior (B) force/displacement curves from donor eye experiment with IOP values of 10, 15, and 20 mmHg. Anterior (C) and posterior (D) force/displacement curves from in silico experiment with 10, 15, and 20 mmHg IOPs. E: Axial corneal stresses under compression from in-silico study at IOP = 15mmHg.
Table 3.
Axial stiffness ratio between anterior and posterior corneal regions in response to varying intraocular pressures.