Corneal collagen crosslinking (CXL) is a treatment used for corneal ectasia, a major cause of impaired vision in the United States and a leading indication for corneal transplantation. Existing methods of measuring the mechanical properties of normal and ectatic corneas still face a number of hurdles, including low spatial resolution, patient motion, measurement speed, patient comfort, and intraocular-pressure dependence. We have recently developed a phase-decorrelation OCT (PhD-OCT) method which avoids these drawbacks. PhD-OCT is sensitive to the endogenous random motion within the cornea. This nanometer-level motion can be detected with 5ms (M-scan) measurements using spectral-domain OCT. The random motion is reduced in crosslinked regions of the cornea, which provides contrast to enable mapping of corneal properties during CXL. These maps agree well with the current understanding of the CXL process, showing a distinct region of increased stiffness in the anterior portion of the cornea which corresponds to the demarcation line sometimes visible in conventional OCT. The PhD-OCT method uses conventional OCT and does not involve perturbing the cornea. This method may be useful clinically for pre-surgical screening, ectasia diagnosis, and treatment monitoring and customization.
|