Extended-imaging-depth (16mm) Spectral Domain OCT Operating at 1310-nm for Anterior Segment Biometry of the Human Eye

Abstract

 

Purpose

 

The aim of this study is to demonstrate the feasibility of an extended-imaging-depth spectral domain OCT (EID-SDOCT) for the comprehensive biometric assessment of the whole anterior segment of the human eye.

 

Methods

 

We have developed an EID-SDOCT, operating at 1310 nm, capable of a comprehensive biometric evaluation of the whole anterior segment from anterior cornea to posterior crystalline lens surface. In the system, a new prototype InGaAs linescan camera with 2048 active-pixel photodiodes is used to record OCT spectral interferograms in parallel. 3D EID-SDOCT imaging of the anterior segment was conducted under a bright (~500 lux) and a dark (<1 lux) stimulus, respectively to examine architectural changes of the whole anterior segment during dynamic light-dependent iris movement. An unwarping algorithm was used to correct the 3D image distortions.

 

Results

 

EID-SDOCT provided a 16 mm imaging depth in air. An A-scan rate of ~120 kHz providing ~7.2 μm axial resolution in air permitted anterior-segment imaging of the human eye ranging from the anterior cornea to the posterior surface of the crystalline lens. During light-dependent iris movement there is an obvious difference of pupil size between the bright (Fig. A) and dark (Fig. B) background conditions. Further, based on the segmentation of the recorded high-resolution 3D OCT images, the 3D biometry of the cornea, angle, anterior chamber and crystalline lens are derived and compared between the two light conditions (see the figure).

 

Conclusions

 

This newly developed EID-SDOCT can be used for whole anterior segment imaging/biometry, including the biometry of the cornea, iris, iridocorneal junction and crystalline lens. It can also be used to provide whole AC depth, lens thickness and total cornea to posterior lens depth in one scan. This performance is comparable to that of state-of-the-art swept-source OCT with similar system specifications. However, EID-SDOCT is more cost-effective, more stable, more reliable and simpler for clinical translation as current commercial OCT systems are based on SD-OCT.

 

 

EID-SDOCT imaging of the anterior segment. Column (A) and (B) respectively correspond to a bright and a dark stimulus. Row (1) provides a 3D reconstruction of the whole anterior segment. Row (2) provides a segmentation of the cornea and angle. Row (3) provides a segmentation of the anterior chamber.

 

Keywords: 421 anterior segment • 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 495 depth