Abstract
Purpose:
Automated eye movement tracking has been used for marketing and advertising research, the development of assistive devices for immobile individuals, video games, and most extensively for neuropsychiatric research. We have developed a novel technique for eye movement tracking while watching a music video in which the position of the eye is tracked based on time elapsed since the start of the video rather than spatial calibration, enabling detection of impaired ability to move one eye relative to the other, and either eye relative to normal controls. The purpose of this work is to demonstrate that this novel tracking algorithm may reveal abnormal eye movement in patients with either a known oculomotor or abducens palsy or mass effect on the oculomotor or abducens nerves.
Methods:
We recorded subjects’ eye movements using an Eyelink 1000 (SR Research, Ltd., Ontario, Canada) eye tracker sampling at 500 Hz over 200 seconds while the subject viewed a music video moving inside an aperture on a computer monitor. We used this technique to assess ocular motility in 125 neurologically and ophthalmologically well control subjects and ten patients with clinical III and/or VIth nerve palsy confirmed by neurophthalmologic examination, or mass effect on the IIIrd or VIth nerve.
Results:
We detected significantly decreased lateral eye movement amplitude and disconjugacy in patients with a sixth nerve palsy apparent on clinical examination. Similar significant decreases in lateral eye movement and conjugacy were seen in subjects with lesions impinging on the VIth nerve. In patients with known oculomotor palsy, significantly decreased vertical eye movement and disconjugacy relative to controls was noted. The decreases were reversible upon resection of the causative mass effect or treatment of underlying pathology and were not seen in control subjects.
Conclusions:
Our results suggest that our novel eye movement tracking algorithm may reveal clinical and subclinical third and sixth nerve palsy in awake patients watching a music video. Since cranial nerve palsies are a signature finding of many neurologic disorders, this methodology renders eye tracking a potentially useful clinical and research tool for assessment of physiologic functioning in a spectrum of pathology including elevated intracranial pressure due to brain injury and/or hydrocephalus.
Keywords: 523 eye movements: conjugate •
524 eye movements: recording techniques •
638 pathology: human