Abstract
Presbyopia is an age-related visual impairment that affects everyone, typically emerging in the forties or early fifties due to the stiffening of the eye’s crystalline lens or extra-lenticular changes that hinder near-focus ability. The conventional corrective solutions, such as reading glasses, progressive addition lenses (PALs), contact lenses, and intraocular lenses, have limitations. Progressive lenses, though widely used, often cause dissatisfaction due to unnatural accommodation, reduced contrast, limited depth perception, and optical distortions, leading to discomfort and motion issues. These challenges highlight the need for a dynamic, adaptive alternative that better mimics natural eye accommodation. The advent of tunable lenses presents a promising opportunity to address these limitations. Early implementations of tunable lens technology utilized piezoelectric-actuated varifocal liquid lenses, while subsequent work integrated time-of-flight distance sensors to adjust focal power based on user head movement. Further studies demonstrated adaptive tuning using liquid membrane lenses, with pupil tracking and stereo camera-based fusion algorithms. While these approaches show promise, limitations remain in response accuracy, natural accommodation emulation, and the effective working distance of stereo cameras. To address these limitations as a part of my doctoral thesis, I used liquid membrane-based tunable lenses from Optotune Inc. (EL-30-45), which change shape using optical fluids and a polymer membrane, offering a tunable range of -3.00 to +3.00 Diopters (D). The input to change the power of the lenses is provided using a current controller provided by the manufacturer, Optotune Inc. I determined the lower order and higher order aberrations of these lenses using a Hartmann-Shack wavefront sensor to ensure that the lenses have good optical quality. Furthermore, I assessed the effectiveness of the tunable lenses subjectively by measuring contrast sensitivity and visual acuity in human participants for use as a corrective lens. I also optimized the linearity of tunable lenses by measuring the achieved focal power for different applied input current values and deriving better focus tuning parameters. Furthermore, a study during my PhD work also demonstrated the feasibility of an adaptive control algorithm using a solid-state Light Detection and Ranging (LiDAR) camera in combination with gaze tracking, enabling dynamic focal adjustments. We developed a functional prototype with the liquid lenses for presbyopia correction. In this previous study, we assessed the performance of a tunable lens prototype in 15 healthy young participants with corrected sphero-cylindrical refraction. Participants completed a dynamic matching task. The task involved viewing and matching targets displayed on three screens positioned at varying distances under two distinct conditions: • Natural accommodation, where their eyes adjusted focus normally. • Simulated presbyopia, induced by cycloplegic drops to temporarily paralyze accommodation, requiring the use of the tunable lens prototype for focusing. The response times and accuracies were measured and found to be comparable between both the conditions, suggesting that real time gaze-tracking technology could effectively control tunable lenses for presbyopia correction.
Author and committee
dc:creator, dc:contributor.*- Author
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- Agarwala, Rajat
Identifiers
dc:identifier.*- Identifier
- hdl:10900/172735