Enhancing Precision in Eye Surgery: Applanation and Vacuum-Aided Automatic Cornea Needle Insertion System

This paper illustrates the improvement of needle positioning precision within corneal tissue by an automated needle insertion system utilizing a vacuum applanation pad. The system is designed to streamline the needle insertion process for deep anterior lamellar keratoplasty (DALK), where precise positioning of the needle tip is essential for successful pneumatic dissection of the diseased corneal tissue. The vacuum applanation pad of the system can fixate and flatten the corneal tissue, resulting in a fixed uniform tissue region. By penetrating the needle into the fixture region, tissue deformation - which can negatively influence needle positioning accuracy - could be minimized. Furthermore, a needle selection process regarding the gauge and length was performed to determine the optimal needle parameter with minimal end tip deflection, and a Luer lock needle fixture was designed to provide roller support that can additionally suppress deflection. Two target needle depths (400 and
$500~\mu \text{m}$
) were set to evaluate the proposed system. Ten cadaveric porcine eyes were tested for each target depth and a total of 20 data points were acquired. As a result, the system could achieve a needle end tip depth of
$373.9\pm 15.9~\mu \text{m}$
(Target:
$400~\mu \text{m}$
) and
$441.3\pm 22.2~\mu \text{m}$
(Target:
$500~\mu \text{m}$
), showing an overall standard deviation of
$21.1~\mu \text{m}$
from the target depth. Therefore, the proposed system could achieve precise positioning of the needle within the corneal tissue to the target depth without relying on feedback information, such as that provided by real-time optical coherence tomography.