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The quality and availability of eye tracking equipment has been increasing while costs have been decreasing. These trends increase the possibility of using eye trackers for entertainment purposes. Games that can be controlled solely through movement of the eyes would be accessible to persons with decreased limb mobility or control. On the other hand, use of eye tracking can change the gaming experience for all players, by offering richer input and enabling attention-aware games. Eye tracking is not currently widely supported in gaming, and games specifically developed for use with an eye tracker are rare. This paper reviews past work on eye tracker gaming and charts future development possibilities in different subdomains within. It argues that based on the user input requirements and gaming contexts, conventional computer games can be classified into groups that offer fundamentally different opportunities for eye tracker input. In addition to the inherent design issues, there are challenges and varying levels of support for eye tracker use in the technical implementations of the games.

Recent evidence on the performance benefits of expanding targets during manual pointing raises a provocative question: Can a similar effect be expected for eye gaze interaction? We present two experiments to examine the benefits of target expansion during an eye-controlled selection task. The second experiment also tested the efficiency of a "grab-and-hold algorithm" to counteract inherent eye jitter. Results confirm the benefits of target expansion both in pointing speed and accuracy. Additionally, the grab-and-hold algorithm affords a dramatic 57% reduction in error rates overall. The reduction is as much as 68% for targets subtending 0.35 degrees of visual angle. However, there is a cost which surfaces as a slight increase in movement time (10%). These findings indicate that target expansion coupled with additional measures to accommodate eye jitter has the potential to make eye gaze a more suitable input modality.

Eye trackers have been used as pointing devices for a number of years. Due to inherent limitations in the accuracy of eye gaze, however, interaction is limited to objects spanning at least one degree of visual angle. Consequently, targets in gaze-based interfaces have sizes and layouts quite distant from "natural settings". To accommodate accuracy constraints, we developed a multimodal pointing technique combining eye gaze and speech inputs. The technique was tested in a user study on pointing at multiple targets. Results suggest that in terms of a footprintaccuracy tradeoff, pointing performance is best (~93%) for targets subtending 0.85 degrees with 0.3-degree gaps between them. User performance is thus shown to approach the limit of practical pointing. Effectively, developing a user interface that supports hands-free interaction and has a design similar to today's common interfaces is feasible.

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