Abstract
Purpose :
The distribution of the Optical Coherence Tomography (OCT) speckle of cornea is thought to be associated with its microstructure. It is hypothesized that there is an influence of intraocular pressure (IOP) on this distribution. Our purpose was to evaluate this relationship in a controlled environment of an ex-vivo study.
Methods :
14 porcine eyes acquired from a local abattoir were measured with spectral-domain OCT (SOCT Copernicus REVO) within the maximum of 8 hours post mortem. A custom-made system was used with a computer-controlled syringe pump that allows delivering a stable set level of IOP to the anterior chamber. The range of IOP was from 10 to 40 mmHg with steps of 5 mmHg. Three horizontal and three vertical OCT B-scans of the central cornea (5 mm) were acquired at each IOP level. Raw data was used for subsequent calculations. The intensity of pixels in OCT scans was assumed to be Gamma distributed. Spatial distribution maps of Gamma parameters (scale parameter aG, shape parameter vG), corresponding to the central stroma, were computed from OCT scans of size 592 x 1529 pixels using 41 x 41 pixel scanning window. Then, a region of interest (ROI) was selected from the maps and values of the shape and scale parameter were averaged from ROI. The nonparametric Wilcoxon sign-rank test was used to evaluate changes in the averaged values of Gamma distribution parameters with IOP.
Results :
Corneal OCT speckle distribution responds to changes in IOP. Statistically significant differences were observed between values of aG parameter at different IOP levels, particularly in the lower range of IOP values from 10 to 20 mmHg (see figure, bottom panel). Such relationship was less evident for the shape parameter vG.
Conclusions :
The study proves that variation in IOP results in changes in corneal OCT speckle statistics. Hence, evaluation of OCT speckle may allow characterizing corneal microstructure and its dependence on IOP.
This is a 2020 ARVO Annual Meeting abstract.