Abstract
Purpose :
The statistics of speckle in optical coherence tomography (OCT) images of cornea are supposed to reflect changes in corneal properties induced by intraocular pressure (IOP). The purpose of this study was to develop a method for estimating IOP using the information of corneal OCT speckle statistics.
Methods :
An inflation test was performed on 23 porcine eyeballs in the ex-vivo study with IOP increasing from 15 to 40 mmHg with a step of 5 mmHg. IOP was precisely set and maintained at each level using a computer-controlled syringe pump. Spectral-domain OCT (SOCT Copernicus REVO) was used to acquire B-scans of the central 5 mm of cornea for each IOP. After initial preprocessing, the region of interest (ROI) of size 600x50 pixels was moved vertically within the imaged stroma in OCT scans with a step of 20 pixels (see figure, top panel). For pixel values from ROI in each position, contrast ratio (CR) was calculated. The obtained trajectories of CR changes with corneal depth were then fitted with linear functions and the correlation between IOP values and the group mean slopes of these functions was calculated.
Results :
IOP elevation influences the shape of the trajectory of CR changes with corneal depth, generally increasing CR values (see figure, left panel). The slope of these trajectories was found to be strongly correlated with IOP, resulting in a Pearson correlation coefficient of R=0.997, p<0.001 (see figure, right panel).
Conclusions :
The results of this ex-vivo study show the potential of OCT speckle statistics to be utilized for measuring IOP using static corneal imaging (i.e., without inducing corneal deformation). Further work is needed to validate this method with in-vivo imaging of human corneas.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.