1.6 MHz Single-Spot OCT Imaging the Whole Anterior Segment

Abstract

 

Purpose:

 

To acquire a densely sampled volumetric OCT dataset of the whole anterior segment within less than 1 second and to demonstrate that high quality OCT imaging of the anterior segment is possible at MHz speeds.

 

Methods:

 

We developed a 1.6 MHz OCT system based on a 1310nm FDML laser which includes specially designed chirped fiber Bragg gratings for cavity dispersion reduction. This new development provides extended coherence length compared to previous MHz OCT systems greatly improving sensitivity roll-off. Imaging range and resolution can be traded off by adjusting the laser sweep range. The laser power onto the cornea was in accordance with ANSI safety standards.

 

Results:

 

The OCT system delivers a shot-noise limited sensitivity of 103dB at 1.6 MHz axial scan rate and features a sensitivity roll-off of 0.75mm/dB. When operated at 100nm (60nm), a 1GHz detection bandwidth provides a total imaging depth range (in air) of about 5.5mm (9mm). The system can acquire a densely sampled cube of 1000 x 1000 depth scans within 0.8 seconds and features very good image quality (see images).In "high resolution mode" (100nm sweep range, ~12um resolution in tissue), the 3D data sets show substructure in the cornea as well as in the iris. In "long range mode" (60nm sweep range), the whole anterior segment from the front of the cornea to the front of the crystalline lens can be imaged with one scan.

 

Conclusions:

 

Unlike previous MHz-OCT, extended depth range MHz-OCT is suitable for anterior segment imaging. Densely sampled cubes of 1000 x 1000 x 500 voxels with very high image quality can be acquired within less than a second.  

 

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • anterior segment