Scanning system design for large scan depth anterior segment optical coherence tomography.

In telecentric scanning a large lateral scan area leads to an increase in the angle of incidence on each of the four anterior ocular surfaces (two for the cornea and two for the crystalline lens), causing significant reduction in the signal obtained from regions farther from the optical axis. We propose an optical coherence tomography scanning system, which achieves nearly normal incidences across the lateral locations of the four ocular surfaces. This provides an increase in the amount of light scattered back to the system, resulting in a higher signal-to-noise ratio (SNR). The images of a model eye obtained with the proposed scan and conventional telecentric scan were compared. SNR improvement of 5dB and 12dB was observed for the anterior and the posterior lens surfaces, respectively. For the posterior corneal surface SNR improvement of 4dB was observed, while the SNR improvement for the anterior corneal surface was 0.7dB.