Analysis of the effects of Eye-Tracker performance on the pulse positioning errors during refractive surgery

• Main Authors: Samuel Arba-Mosquera, Ioannis M. Aslanides
• Format: Article
• Language: English
• Published: Elsevier 2012-01-01
• Series: Journal of Optometry
• Subjects: Eye-Tracker; Pulse positioning errors; Refractive surgery; Eye-Tracking; Positioning errors; Eye movements; Acquisition rate; Latency time; Scanner positioning time; Laser firing rate; Trigger delay
• Online Access: http://www.sciencedirect.com/science/article/pii/S1888429612000039

Purpose: To analyze the effects of Eye-Tracker performance on the pulse positioning errors during refractive surgery. Methods: A comprehensive model, which directly considers eye movements, including saccades, vestibular, optokinetic, vergence, and miniature, as well as, eye-tracker acquisition rate, eye-tracker latency time, scanner positioning time, laser firing rate, and laser trigger delay have been developed. Results: Eye-tracker acquisition rates below 100 Hz correspond to pulse positioning errors above 1.5 mm. Eye-tracker latency times to about 15 ms correspond to pulse positioning errors of up to 3.5 mm. Scanner positioning times to about 9 ms correspond to pulse positioning errors of up to 2 mm. Laser firing rates faster than eye-tracker acquisition rates basically duplicate pulse-positioning errors. Laser trigger delays to about 300 μs have minor to no impact on pulse-positioning errors. Conclusions: The proposed model can be used for comparison of laser systems used for ablation processes. Due to the pseudo-random nature of eye movements, positioning errors of single pulses are much larger than observed decentrations in the clinical settings. There is no single parameter that ‘alone’ minimizes the positioning error. It is the optimal combination of the several parameters that minimizes the error. The results of this analysis are important to understand the limitations of correcting very irregular ablation patterns.