Optical coherence tomography with a 2.8-mm beam diameter and sensorless defocus and astigmatism correction.

An optical coherence tomography (OCT) system with a 2.8-mm beam diameter is presented. Sensorless defocus correction can be performed with a Badal optometer and astigmatism correction with a liquid crystal device. OCT B-scans were used in an image-based optimization algorithm for aberration correction. Defocus can be corrected from ? 4.3 ?? D to + 4.3 ?? D and vertical and oblique astigmatism from ? 2.5 ?? D to + 2.5 ?? D . A contrast gain of 6.9 times was measured after aberration correction. In comparison with a 1.3-mm beam diameter OCT system, this concept achieved a 3.7-dB gain in dynamic range on a model retina. Both systems were used to image the retina of a human subject. As the correction of the liquid crystal device can take more than 60 s, the subject’s spectacle prescription was adopted instead. This resulted in a 2.5 times smaller speckle size compared with the standard OCT system. The liquid crystal device for astigmatism correction does not need a high-voltage amplifier and can be operated at 5 V. The correction device is small ( 9 ?? mm × 30 ?? mm × 38 ?? mm ) and can easily be implemented in existing designs for OCT.