Abstract
Purpose: :
To visualize corneal ultrastructure and tear film dynamics in 3D with spectral domain optical coherence tomography (SOCT) exhibiting 2µm axial resolution at 100.000 A-scans per second.
Methods: :
We employ high-resolution spectral domain optical coherence tomography exhibiting a resolution in tissue of 2µm. The system is equipped with modern high-speed CMOS detector technology, allowing acquisition speeds of 100.000 A-scans/second. Such speed is a prerequisite if precise anatomy is to be determined. The high resolution gives access to corneal microstructure such as the epithelium layer as well as the boundaries of Bowman layer and stroma. Even more interestingly the natural tear film can be distinguished on the cornea surface. High-speed time series of volumes have been recorded in order to study the time evolution of tear film integrity.
Results: :
High-speed corneal tomograms have been recorded at an A-scan rate of 100.000 scans per second. A full volume of 1000 x 100 x 800 pixels is recorded in only 1 sec exhibiting an axial resolution of less than 3µm. Layer boundaries such as the Bowman - Epithelium layer interface can be extracted with high accuracy of 1µm. This allows for precise determination of epithelium layer thickness of 48.71µm±1,05µm and of the Bowman layer thickness of 15.43µm±2.7µm over a diameter of 4mm. The extracted tear film thickness amounted to 5µm. Reducing the scanning pattern to 500x100 points allows even recording several volumes per second. This allowed for studying dynamically break up of natural tear film over time.
Conclusions: :
We produced precise thickness maps of cornea substructure using a high performance FDOCT system with unprecedented imaging speed of the anterior eye anatomy. Such high performance system will gives insight into high fidelity 3D corneal microstructure helping to precisely plan refractive surgery, as well as yields new perspectives on studying and understanding tear film dynamics in a natural environment.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • cornea: epithelium • cornea: tears/tear film/dry eye