Abstract
Purpose :
Subretinal injection is an effective way to deliver therapeutic agents into the photoreceptors and RPE layers. However precise positioning of the injector tip is highly challenging using a surgical microscope. This study explores using a handheld common-path swept-source optical coherence tomography (CP-SSOCT) fiber probe integrated microinjector system to monitor the position of the needle tip and achieve precise subretinal injection using live porcine models.
Methods :
The proposed microinjector was composed of a 3D-printed handpiece, a medical polyimide tube (ID = 0.1 mm), and a fiber sensor glued inside a 23G short-beveled needle with a fixed offset of ~500 um, shown in Fig. 1 (a). The animal studies were conducted using 5 live pigs (N = 10). In each study, retinal surgeons inserted the trocar and needle that was visualized with OCT images, shown in Fig. 1(b). Sodium hyaluronate (Healon) was injected once the needle moved to the target depth. For each porcine eye, two surgeons performed subretinal injections using either the Leica surgical microscope or the proposed microinjector. The trans-vitreal and trans-scleral injections were performed in 8 and 2 eyes. Following the experiments, the injection depth and the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) of the OCT images were measured.
Results :
For all tests, the iatrogenic retinal detachments were produced after subretinal injections. Fig.2 shows a representative Leica microscopic image and OCT image of a live porcine eye. Our proposed system provided an additional cross-sectional view for surgical guidance. The SNR of OCT images in the prepoking and drift stages was 3.16 and 7.19, while the CNR of OCT images was 2.31 and 6.28, respectively. The positioning tracking data in Fig. 1(b) demonstrated that our microinjector system can guide the needle fast and stably, with an average completion time of 12 s. Due to the physiological hand tremor, the root mean square error of the penetration depth is ~64.05 um.
Conclusions :
The proposed endoscopy OCT prototype can monitor the axial motion of the needle tip to increase the precision of subretinal injection, which shows its strong potential for clinical applications.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.