Anterior segment OCT is a key quantitative tool for geometrical, and structural information of the cornea and the ctystaline lens, as well as their dynamics. We have available in our laboratory two custom-built anterior segment optical coherence tomography systems, a spectral OCT and a swept source OCT.
The spectral domain system is based on fiber-optics Michelson interferometer configuration with a superluminescent diode SLD (central wavelength of 840 nm, and 50 nm bandwidth) serving as a source and a 12-bit line-scan CMOS camera . The horizontal and vertical scanning is achieved with two galvanometer optical scanners. The axial resolution of this system was measured to be about 3.4 microns in air. A high acquisition rate, up to 135,000 A-scans/second enables three-dimensional reconstruction allows anterior segment during lenticular accommodation, and corneal deformation dynamic imaging.
The anterior segment images obtained from OCT are subject to fan (arising from the scanning architecture) and optical distortion (arising from refraction from preceding ocular surfaces). We have developed algorithms based on 3-D ray tracing for the compensation of these distortions, which, along with image processing tools for denoising, segmentation and surface fitting) allow quantitative anterior and posterior cornea and anterior and posterior lens topograhies.
Applications of the instruments and processing tools developed include the study of the accommodating lens, corneal biomechanics, crystalline lens gradient index, corneal topography in diseased and treated corneas, study of intracorneal rings, 3-D full biometry in patients implanted with accommodating IOLs, IOL tilt and decentration measurements, among others.