Lightweight Smart Autofocusing Eyeglasses

Abstract

More than 100 million people in the United States of America alone suffer from age-related presbyopia caused by a loss of focal accommodation of the eye crystalline lens as the lens stiffens with age. The resulting accommodative error or lag produces blurred images of objects placed at different distances. Conventional fixed uniform or graded power eyeglasses cannot provide accommodation thus resulting in significant visual impairment. In this paper we will discuss the implementation of lightweight auto-focusing eyeglasses that augment the accommodative range thus partially or fully restoring normal vision function. The paper discusses some aspects of the construction of tunable power eyepieces and the implementation of accommodation correction algorithms.

Keywords: Biomedical optics; accommodation loss; adaptive eyeglasses; presbyopia.

Figure 1.

Illustration of typical Duane’s accommodation amplitude vs age curve [4] for the human eye. The accommodation is reduced from roughly 12 D to about 1 D after age 50.

Figure 2.

(a) Example of typical S-type accommodative response [5] for the human eye. The curve slope progressively flattens for the high powers with age. Furthermore the curve may exhibit offsets and flat regions at low stimulus.

Figure 3.

Simplified schematic of the tunable-focus lens excluding actuators [9]

Figure 4.

(left) Photograph of the actual device, and (right) lens optical power as a function of actuator voltage [9].

Figure 5.

Photograph of a second generation smart eyeglasses with exposed temple compartments.

Figure 6.

Optical setup utilized for imaging an object through a tunable lens eyepiece [9]. The fixed lens and camera emulates the response of a fully presbyopic eye with zero accommodation.

Figure 7.

Imaging of objects through optical setup of Figure 6 emulating a fully presbyopic eye with accommodation provided only by the variable power eyepiece. Images were recorded using our test unable focus eyepiece at optical powers of +0 D (left), and at +3.5 D (right)..

Figure 8.

Variable power setup used to emulate the accommodative response of an eye. The accommodation response is provided by the programmed power of the variable lens as a function of object distance.

Figure 9.

(left) Example of a model accommodative deficiency response for a hyperopic presbyopia eye. The model curve was programmed in the optical setup shown in Figure 8. (right) Accommodative response versus accommodative stimulus for the model prebyopic eye (red) and compensated by the smart eyeglass (green). Note that the smart eyeglass algorithm restores the lost accommodation with good fidelity.