Fiber probe design for needle tip depth sensing in subretinal injection surgery based on SD-OCT

At present, there have been many studies using OCT technology to assist subretinal injection surgery. One of the research directions is to perceive the depth of needle penetration by collecting A-Line signal of tissue in real time. Most of the OCT systems in such solutions use a common optical path architecture, which basically does not require dispersion compensation, and the structure is simple, but the working distance is fixed. In this paper, a needle tip depth sensing SD-OCT system was developed. Two types of ball lens fiber probes emitting quasi-parallel light were designed for use in air and water. The ball lens fiber probe used in water was fabricated. A probe, called a single-mode fiber probe, was manufactured by cutting the light emitting surface of a single-mode fiber using a fiber cleaver. Under the same conditions, in the water, the A-Line signal of the mirror collected by the SD-OCT system integrated with the ball lens fiber probe used in the water is stronger than that collected by the SD-OCT system integrated with the single-mode fiber probe. When collecting the A-Line signal of the mirror in water, the SD-OCT system integrated with the ball lens fiber probe used in the water has a longer working distance than the CP-SDOCT system integrated with the single-mode fiber probe. Finally, the needle tip depth sensing function of the system was tested through experiments.