Automated video tracking of contact lens motion

摘要

Successful extended contact lens wear requires lens motion that provides adequate tear mixing to remove ocular debris. Proper lens motion of rigid contact lenses is also important for proper fitting. Moreover, a factor in final lens comfort and optical quality for contact lens fitting is lens centration. Calculation of the post lens volume of rigid contact lenses at different corneal surface locations can be used to produce a volume map. Such maps often reveal channels of minimum volume in which lenses may be expected to move, or local minima, where lenses may be expected to settle. To evaluate the utility of our volume map technology and evaluate other models of contact lens performance we have developed an automated video-based lens tracking system that provides detailed information about lens translation and rotation. The system uses standard video capture technology with a CCD camera attached to an ophthalmic slit lamp biomicroscope. The subject wears a specially marked contact lens for tracking purposes. Several seconds of video data are collected in real-time as the patient blinks naturally. The data are processed off-line, with the experimenter providing initial location estimates of the pupil and lens marks. The technique provides a fast and accurate method of quantifying lens motion. With better contact lens motion information we will gain a better understanding of the relationships between corneal shapes, lens design parameters, tear mixing, and patient comfort.