Accommodative Haptics Study Based on Flexible Amplification Mechanism

A B S T R A C T

In this study, we take the effect of the anterior movement of the optic into account and propose a novel haptic based on lever-type and bridge-type flexible amplification mechanisms. Based on the consideration of the offset of the rotation center of the flexible hinge, we have deduced the formula for calculating the amplification ratio of the proposed four-stage amplifier. The geometric parameters and the material property parameters, in terms of the clinical measurement data of the human eye, are assumed to restrain the structural features and motion trajectories for the amplifier. As the ciliary muscle achieves the contraction limit, the output displacement and amplification ratio reach the highest and lowest values, separately, and gradually approach a stable range. The amplification ratio of formula calculation and FEA (Finite Element Analysis) are around 18.86 and 17.79, respectively, with the input displacement ranging from 0.115mm to 0.127mm. The error of the amplification ratio between theoretical method and FEA is less than 5%. The presented haptic acting as a four-stage displacement amplifier, enables an improved lens power of 3.80 diopters to obtain much more focus shift to achieve a better near visual performance for patients.

Keywords

Haptic, flexible amplification mechanism, amplification ratio, flexure hinges

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Qiuyue Du Wenjing Chen Bin Tian Wenjing Wang

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References

1. Beiko GH (2013) Comparison of visual results with accommodating intraocular lenses versus mini-monovision with a monofocal intraocular lens. J Cataract Refract Surg 39: 48-55. [Crossref]
2. Ni Y, Deng ZQ, Li JB, Wu X, Li L (2015) Multi-objective Design Optimization of an Over-constrained Flexure-based Amplifier. Algorithms 8: 424-434.
3. Tan N, Zheng D, Ye J (2014) Comparison of Visual Performance after Implantation of 3 Types Intraocular Lenses: Accommodative, Multifocal, and Monofocal. Eur J Ophthalmol 24: 693-698. [Crossref]
4. Dhital A, Spalton DJ, Gala KB (2013) Comparison of near vision, intraocular lens movement, and depth of focus with accommodation and monofocal intraocular lenses. J Cataract Refract Surg 39: 1872-1878. [Crossref]
5. Shusheng B, Shanshan Z, Xiaofeng Z (2010) Dimensionless design graphs for three types of annulus-shaped flexure hinges. Precis Engineer 34: 659-666.
6. Ling M, Cao J, Zeng M, Lin J, Inman DJ (2016) Enhanced Mathematical Modeling of the Displacement Amplification Ratio for Piezoelectric Compliant Mechanisms. Smart Mater Struct 25: 075022.
7. Choi KB, Lee JL, Kim GH (2012) A Compliant Parallel Mechanism with Flexure-based Joint Chains for Two Translations. Int J Precision Engineer Manufactur 13: 1625-1632.
8. Marcos S, Oritiz S, Merino PP, Birkenfeld J, Durán S et al. (2014) Three-dimensional evaluation of accommodating intraocular lens shift and alignment in vivo. Ophthalmology 121: 45-55. [Crossref]
9. Uthoff D, Haigis W, Hepper D, Pölzl M, Holland D (2013) Evaluation of The Valence Objective and Subjective Methods for Measuring Pseudophakic Accommodation. Ophthalmologe 110: 441-446. [Crossref]
10. Dao TP, Huang SC (2017) Design and Multi-objective Optimization for a Broad Self-amplified 2-DOF Monolithic Mechanism. Sādhanā 42: 1527-1542.
11. Ai WJ, Xu QS (2014) New Structural Design of a New Compliant Gripper Based On the Scott-Russell Mechanism. Int J Adv Robotic Syst 2014: 2588-2593.
12. Kim H, Ahn D, Gweon D (2012) Development of a novel 3-degrees of freedom flexure based positioning system. Rev Sci Instrument 83: 055114. [Crossref]
13. Kohnen T, Koch DD (2006) Cataract and Refractive Surgery. Berlin: Springer-Verlag.
14. Zelenika S, Munteanu MG, Bona FD (2009) Optimized flexural hinge shapes for microsystems and high-precision applications. Mech Mach Theor 44: 1826-1839.
15. Yanoff M, Duker JS (2013) Ophthalmology: Expert Consult: Online and Print (4 Edition). Canada: Saunders.
16. Na TW, Choi JH, Jung JY, Kim HG, Han JH et al. (2016) Compact Piezoelectric Tripod Manipulator Based On A Reverse Bridge-Type Amplification Mechanism. Smart Material Struct 25: 13. [Crossref]
17. Liu YC, Wilkinns M, Kim T, Malyugin B, Mehta JS (2017) Cataracts. Lancet 390: 600-612. [Crossref]
18. Tian Y, Shirinzadeh B, Zhang D, Zhong Y (2010) Three flexure hinges for compliant mechanism designs based on dimensionless graph analysis. Precis Engineer 34: 92-100.
19. Wei qing H, Xiao qing S, Yin W (2015) Design of Diamond Piezoelectric Micro Displacement Amplification Mechanism. Optics Precision Engineer 23: 803-809.
20. Pei X, Yu JJ, Zong GH, Bi S (2014) Design of Compliant Straight-line Mechanisms Using Flexural Joints. Chin J Mech Engineer 27: 146-153.
21. Yang Z, He Z, Li D, Xue GM, Cui X (2014) Hydraulic Amplifier design and Its Application to Direct Drive Servo Valve Based on Magnetostricive Actuator. Sensor Actuat A-Physic 216: 52-63.
22. Zhang K, Zhang L, Fu L, Li S, Chen H et al. (2013) Magnetostrictive resonators as sensors and actuators. Sensor Actuat A:Physic 200: 2-10.
23. Sun X, Yang B (2017) A New Methodology for Developing Flexure-hinged Displacement Amplifiers with Micro-vibration Suppression for A Giant Magnetostrictive Micro Drive System. Sensor Actuat A: Physic 263: 30-43.
24. Pallikaris LG, Kontadakis GA, Portaliou DM (2011) Real and pseudoaccommodation in accommodative lenses. J Ophthalmol 2011: 284961. [Crossref]