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

PurposeTo analyze the effects of Eye-Tracker performance on the pulse positioning errors during refractive surgery.MethodsA 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.ResultsEye-tracker acquisition rates below 100Hz correspond to pulse positioning errors above 1.5mm. Eye-tracker latency times to about 15ms correspond to pulse positioning errors of up to 3.5mm. Scanner positioning times to about 9ms correspond to pulse positioning errors of up to 2mm. Laser firing rates faster than eye-tracker acquisition rates basically duplicate pulse-positioning errors. Laser trigger delays to about 300μs have minor to no impact on pulse-positioning errors.ConclusionsThe 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