Semiautomated intraocular laser surgery using handheld instruments

Abstract

Background and Objective
In laser retinal photocoagulation, hundreds of dot-like burns are applied. We introduce a robot-assisted technique to enhance the accuracy and reduce the tedium of the procedure.

Materials and Methods
Laser burn locations are overlaid on preoperative retinal images using common patterns such as grids. A stereo camera/monitor setup registers and displays the planned burn locations overlaid on real-time video. Using an active handheld micromanipulator, a 7x7 grid of burns spaced 650 μm apart is applied to both paper slides and porcine retina in vitro using 30 ms laser pulses at 532 nm. Two scenarios were tested: unaided, in which the micromanipulator is inert and the laser fires at a fixed frequency, and aided, in which the micromanipulator actively targets burn locations and the laser fires automatically upon target acquisition. Error is defined as the distance from the center of the observed burn mark to the preoperatively selected target location.

Results
An experienced retinal surgeon performed trials with and without robotic assistance, on both paper slides and porcine retina in vitro. In the paper slide experiments at an unaided laser repeat rate of 0.5 Hz, error was 125±62 μm with robotic assistance and 149±76 μm without (p < 0.005), and trial duration was 70±8 s with robotic assistance and 97±7 s without (p < 0.005). At a repeat rate of 1.0 Hz, error was 129±69 μm with robotic assistance and 166±91 μm without (p < 0.005), and trial duration was 26±4 s with robotic assistance and 47±1 s without (p < 0.005). At a repeat rate of 2.0 Hz on porcine retinal tissue, error was 123±69 μm with robotic assistance and 203±104 μm without (p < 0.005). Conclusion Robotic assistance can increase the accuracy of laser photocoagulation while reducing the duration of the operation.