Eye Tracker Accuracy: Quantitative Evaluation of the Invisible Eye Center Location

Purpose. We present a new method to evaluate the accuracy of an eye tracker based eye localization system. Measuring the accuracy of an eye tracker's primary intention, the estimated point of gaze, is usually done with volunteers and a set of fixation points used as ground truth. However, verifying the accuracy of the location estimate of a volunteer's eye center in 3D space is not easily possible. This is because the eye center is an intangible point hidden by the iris. Methods. We evaluate the eye location accuracy by using an eye phantom instead of eyes of volunteers. For this, we developed a testing stage with a realistic artificial eye and a corresponding kinematic model, which we trained with {\mu}CT data. This enables us to precisely evaluate the eye location estimate of an eye tracker. Results. We show that the proposed testing stage with the corresponding kinematic model is suitable for such a validation. Further, we evaluate a particular eye tracker based navigation system and show that this system is able to successfully determine the eye center with sub-millimeter accuracy. Conclusions. We show the suitability of the evaluated eye tracker for eye interventions, using the proposed testing stage and the corresponding kinematic model. The results further enable specific enhancement of the navigation system to potentially get even better results

Development of a head-mounted, eye-tracking system for dogs

Growing interest in canine cognition and visual perception has promoted research into the allocation of visual attention during free-viewing tasks in the dog. The techniques currently available to study this (i.e. preferential looking) have, however, lacked spatial accuracy, permitting only gross judgements of the location of the dog’s point of gaze and are limited to a laboratory setting. Here we describe a mobile, head-mounted, video-based, eye-tracking system and a procedure for achieving standardised calibration allowing an output with accuracy of 2-3º. The setup allows free movement of dogs; in addition the procedure does not involve extensive training skills, and is completely non-invasive. This apparatus has the potential to allow the study of gaze patterns in a variety of research applications and could enhance the study of areas such as canine vision, cognition and social interactions

The influence of corneoscleral topography on soft contact lens fit

To evaluate the influence of peripheral ocular topography, as evaluated by optical coherence tomography (OCT), compared with traditional measures of corneal profile using keratometry and videokeratoscopy, on soft contact lens fit

Eye tracking based navigation for proton beam therapy

Cancers of the eye, so-called ocular tumors, are a severe disease that may lead to blindness or even death if left untreated. A possibility to remove the tumor from the body of the patient is a so-called enucleation surgery, the removal of the eye. However, it is a drastic action and oncologists usually try to avoid it. Another treatment option is the therapy with protons. The actual proton therapy to treat ocular tumors is very successful and non-invasive. However, the navigation method that is applied for this kind of therapy requires a pre-treatment surgery, where radio-opaque clips are sutured onto the affected eyeball. These clips are used during the actual treatment to align the diseased eye with two orthogonal X-ray units. Hence, the overall treatment is invasive. The work at hand presents an alternative, completely non-invasive navigation method based on eye tracking technology. We present a new treatment scheme with a first eye tracking prototype integrated into the treatment facility at Paul Scherrer Institute (PSI). This system together with a patient specific eye model enables the medical physicist to align the patient’s eye such that the tumor gets accurately treated by the proton beam. Further, we present a second, improved eye tracking system. This time, we propose a stereo eye tracker, which only uses one physical camera to save physical space. We combine a stereo eye tracking algorithm with a clever arrangement of two planar mirrors and a single camera to get high accuracy, precision, and a compact design altogether. Finally, we present a method to quantitatively evaluate the proposed navigation system. Verifying the accuracy of the location estimate of a volunteer’s eye center is not easily possible. This is because the eye center is an intangible point, that does not correspond to an anatomical structure. Our evaluation method is based on an eye phantom on microstages and a corresponding kinematic model. Our research and development may lead to an ocular tumor treatment which will be safer, more cost-effective, and more accessible to patients suffering from this serious disease