Optical Coherence Elastography-Based Corneal Strain Imaging During Low-Amplitude Intraocular Pressure Modulation.

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Materials Science

Background:

• Optical coherence elastography (OCE) offers high-resolution strain imaging for ocular tissues.
• Intraocular pressure (IOP) is a key factor inducing strain in the eye, with physiological diurnal fluctuations up to 5 mmHg.

Purpose of the Study:

• To investigate local corneal strain patterns under low-amplitude intraocular pressure (IOP) modulation.
• To assess the sensitivity and capabilities of OCE in detecting small deformations in corneal tissue.

Main Methods:

• Ex vivo porcine eyes were subjected to controlled IOP changes (5 mmHg cycles) around initial pressures of 15 mmHg and 25 mmHg.
• Two-dimensional optical coherence tomography (2D-OCT) B-scans were acquired to generate axial strain maps from displacement and phase data.
• Strain detection sensitivity was quantified, with a reliable measurement threshold of 2.44·10⁻⁵ established.

Main Results:

• OCE resolved deformations from single 1-mmHg IOP steps.
• Largest strain amplitudes (5.11·10⁻³) occurred in the posterior stroma at lower IOP (15 mmHg vs. 25 mmHg, p=0.003).
• Corneal response showed anterior compression and posterior expansion upon IOP increase; tissue changes were sensitive to postmortem time.

Conclusions:

• Low-amplitude IOP variations, mimicking diurnal changes, induce measurable corneal deformations.
• Axial strain maps enable localized assessment of the corneal biomechanical response.
• Small-strain OCE shows potential for broader applications beyond ocular tissues.