Anterior Segment Optical–Frequency–Domain– Reflectmeter Optical Coherence Tomography Using SSG–DBR Laser (2nd Report)

Abstract

Purpose: : Anterior segment imaging by Optical Coherence Tomography (OCT) has been reported by several investigators. Their system is called Time–Domain OCT (TD–OCT). We have tried to develop a novel application for Optical–Frequency–Domain–Reflectmeter OCT (OFDR–OCT) that will provide a higher speed and a longer depth range compared with TD–OCT. We demonstrated the efficiency of a first–generation application for OFDR–OCT (Mk–I) using SSG–DBR laser at the 2005 ARVO. We improved the speed of SSG–DBR laser and developed a second–generation application for OFDR–OCT (Mk–II) capable of eliminating motion artifacts. The purpose is to evaluate the efficiency of Mk–II.

Methods: : Our OFDR–OCT utilizes SSG–DBR laser capable of emitting 3.1 mW of high–coherence light discretely. The frequency interval was 6.25 GHz, corresponding to 12 mm depth range. The tuning range of SSG–DBR laser was from 1533 to 1574 nm to achieve an axial resolution of 20 µm, an lateral resolution of 26 µm. The laser probe was mounted on slitlamp base. It was performed with the normal subjects and subjects with open angle glaucoma and subjects with narrow angle glaucoma, subjects after LASIK in sitting position.

Results: : The scanning speed was 2.5 kHz axial scans per second and image frame was selectable between 128 and 512 axial scans per image. The image size was 8 mm wide and 6 mm deep. We can observe changes in anterior segment anatomy after laser iridotomy and filtering blebs after trabeculectomy and measure corneal pachymetry after LASIK with little motion artifacts.

Conclusions: : This system enables the evaluation of anterior segment in both quantity and quality, and useful for avoiding the risk of the infection.

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