Switchable liquid crystal contact lenses: dynamic vision for the ageing eye

Abstract

The inability of the eye to focus on nearby objects, presbyopia, is suffered by ~100% of people over the age of 50. Liquid crystal (LC) spectacle lenses have shown great potential for correcting presbyopia. However, correcting presbyopia in contact lens users has proven elusive and existing commercial options suffer significant compromises in vision and comfort. We describe a novel contact lens that includes a liquid crystal element that offers to correct presbyopia without the compromises associated with other technologies. We fabricated variable focus lenses using a balanced optical system, providing the additional optical power presbyopes require for near vision (typically +1.00 D to +2.00 D). The system uses positive optical power from the two substrates and variable negative optical power from the LC layer to form a balanced optical system which, when unpowered, corrects distance vision. Upon voltage application, the liquid crystal layer decreases in refractive index, resulting in additional optical power in the system, offering correction equivalent to reading glasses. Our new technology is based on a traditional contact lens material which could be placed directly on the eye. The liquid crystal lens employed is well suited to the small optical areas associated with contact lenses. We compare several different LC materials and geometries which are suitable for our application, and discuss the influence of material and geometry on switching times, optical quality and operating voltage. Our contact lenses typically switch ±2.00D in response to < 10 V rms with response times of the order of a second.

Liquid crystal contact lenses with graphene electrodes and switchable focus

“…planar aligned with ITO electrodes, planar aligned with graphene electrode and homeotropic aligned, were characterized for their optical and electrical properties [2][3][4][5]. Polarizing microscopy images of the contact lens revealed the quality of the alignment both for planar [2,5] and homeotropic geometry.…”

“…One of the first successfully created electrically switchable liquid crystal contact lenses utilized the planar aligned geometry [2,3]. Figure 1 shows the design and geometry of the substrates and the liquid crystal layer between them, which dictate the optical power of the complete system.…”

“…Polymethyl methacrylate (PMMA) substrates have been employed in various lens designs [2][3][4] mainly due to their historic link with the contact lens industry. The lower PMMA substrate has to been designed with its radius of curvature matching that of the corneal dimensions (typically a 7.8 mm radius of curvature) for optimum placement on the eye.…”

“…A unique and extremely promising approach is the use of liquid crystal contact lenses that can provide compromise-free vision in the whole field of view. A distinguishing feature of such liquid crystal contact lenses is the ability to provide additional optical power for near vision tasks on application of low voltages (ON state) with the eye able to perform distance vision tasks normally in the OFF state of the contact lens [2][3][4]. The change in optical power is facilitated by the changing refractive index of the liquid crystal system on application of a voltage and can be continuous, offering mid-distance vision correction.…”

“…We report the electro-optical performance of such contact lens systems in two different modes of liquid crystal geometry; planar (homogeneous) [2,3] and vertically aligned (homeotropic) [4]. We further describe the optimisation of such systems with the inclusion of graphene electrodes instead of Indium Tin Oxide electrodes (ITO) [5].…”