1. Field of the Invention
This invention relates to spectacles. In particular, it relates to automatic accommodative spectacles that use sensors to determine a patient's fixation region of interest (ROI) and automatically adjust the optical power of focusing elements on the spectacles to help him/her remain focused on the fixation ROI.
2. Description of the Related Art
Spectacles and contact lenses are commonly used optical devices to correct refractive errors, such as myopia (nearsightedness) and hyperopia (farsightedness). Most prescribed spectacles and contact lenses are unifocal that have one fixed optical power. Unfortunately, patients' refractive errors can change overtime and unifocal correction devices cannot adapt to such changes. In addition, patients with presbyopia, that is, people who cannot accommodate due to aging, need different optical powers to clearly see targets at various distances. In recent years, accommodative intraocular lenses (A-IOL) have been reported, such as U.S. Pat. No. 6,616,691, US patent application 2006/0089712. But A-IOL can only be implanted in patients' eyes after cataract surgeries. A number of multifocal spectacles and contact lenses have been proposed and/or produced; they can provide either a few discrete number of optical power or continuous varying optical powers (U.S. Pat. Nos. 3,877,798, 3,975,093 and 4,472,036), which usually requires the patients to use different regions of the devices or look at targets in specific fashions, significant constraints on how patients look at their targets of interest.
A focusing element is an optical device that can vary its focusing capability. There are a number of methods to achieve variable focus. Some variable focus lenses have been proposed/produced to make spectacles (U.S. Pat. Nos. 5,956,183, 6,517,203, 7,553,019, and US patent application 2010/0053543). However, in these proposals, how to determine the needed optical power of the lenses are not specified. The amount of optical power adjustment is usually based on the feedback from visual perception. Such devices can be useful for patients in certain cases where the viewing targets are stationary or changing infrequently, but are not practical for general usage.