Simultaneous OCT A-scan depth ranging and C-scan volume imaging for intraoperative robotic retinal surgery guidance

Current subretinal injection systems combine surgical microscopy, optical coherence tomography (OCT), and robotic assistance to enable precise, depth-resolved, and tremor-free drug delivery to targeted retinal sites. Nevertheless, subretinal and intraretinal vascular injections remain constrained by two major challenges: (1) the inherent difficulty in simultaneously achieving wide-field, real-time imaging of fundus lesions at high spatial resolution, and (2) the requirement for precise intraocular localization of the needle tip quickly. Current fundus injection imaging methods provide limited accuracy in needle tip localization and require prolonged procedure time. To address this issue, we present a novel intraoperative OCT (iOCT) imaging system that integrates a single light source and dual-channel OCT detection to simultaneously acquire A-scan and C-scan data without incurring substantial additional cost. Using the A-scan component of the synchronization signal, high-speed and real-time distance detection of the retinal surface is performed in M-scan mode. Meanwhile, the C-scan component of the synchronization signal provides high spatial resolution imaging of retinal depth information. Combined with the ultra-wide field of view afforded by microscopic imaging, this approach facilitates rapid and extensive guidance for lesion localization in the fundus, while also allowing real-time intraoperative assessment of drug injection procedures. This system is integrated into a high-precision robot-assisted platform, enabling subretinal injections and retinal vascular injections within the ocular fundus. To the best of our knowledge, this is the first time that the simultaneous acquisition of A-scan and C-scan data has been proposed for subretinal injection and retinal vascular injection procedures. The A-scan sensitivity roll-off was characterized and exhibited a decrease of approximately 3 dB over a 0.88 mm depth range in water. The B-scan imaging with 1024 × 1024 pixels achieve a 97.7 fps with maximal lateral field of view (FOV) 16 mm. The system achieved an axial measurement accuracy of 15 µm for needle tip localization. The success rate of single attempt subretinal (6 out of 6 attempts) and optic disc vessel injections was 100% in both live (3 out of 3 attempts) and <i>ex vivo</i> pig eyes (100 out of 100 attempts/30 out of 30 attempts), while venous injections in live pig eyes required positional adjustments during injection to achieve a 100% success rate (3 out of 3 attempts). Integrated with a microscope, the A-scan and C-scan OCT system, assisted by a robotic arm, can safely and reliably address the challenges associated with subretinal injection and retinal vascular injection.