The use of high-resolution eye-tracking to determine the impact of ocular nerve palsy on ocular movement and recovery

Introduction: Recent technology allows precise eye movement measurement, improving diagnosis, management, and intervention planning. Such programmes are rarely used in clinical practice due to limited programmes and analysis techniques. Aims: To develop testing paradigms and analysis techniques to record eye movements in a clinical setting and to monitor the impact of recently acquired ocular nerve palsies on eye movement systems within four months of onset. Methods: Thirty-five age-matched healthy control participants aged 19-79 years were divided into three age categories; 18-39 years, 40-59 years and >60 years. The fixation, smooth pursuit and saccades were recorded. Ten patients, mean age 72.4 ±10.5 years, who had acquired ocular nerve palsy related to diabetes, hypertension, and high cholesterol were enrolled. They completed five eye movement recording measurements (in weeks 2, 4, 8, 12 and 16 post-onset) of the affected eye using EyeLink 1000 Plus with a 500 Hz sampling rate. Ethical approval was obtained from the Research Ethics Committee NHS, Health Research Approval. Results: An increase in smooth pursuit root means square error and prolonged saccadic latency, tested horizontally and vertically, were identified in the old age healthy volunteers (p<0.05). The saccadic gain of the older age group reduced at larger horizontal amplitude and upward saccades (p<0.05). Conversely, the horizontal and downward saccadic peak velocity increased with ageing. All ten patients with microvascular ocular nerve palsy had impaired smooth pursuit and saccadic performance at baseline, with varying recovery rates over 4 months. These were commensurate with the clinical findings. Conclusion: The EMR technique, programmes, and analysis strategies are simple-to-use technology that generates a permanent record and reproducible results. Additionally, it can assist clinicians in making decisions during the recovery period of patients with acquired ocular nerve palsies. The findings yielded encouraging results which merit further investigation and development.