{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,12]],"date-time":"2025-11-12T05:16:14Z","timestamp":1762924574935,"version":"3.45.0"},"reference-count":55,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2025,11,10]],"date-time":"2025-11-10T00:00:00Z","timestamp":1762732800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100007569","name":"Carl Zeiss Foundation","doi-asserted-by":"publisher","award":["P2019-01-001"],"award-info":[{"award-number":["P2019-01-001"]}],"id":[{"id":"10.13039\/100007569","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Bioengineering"],"abstract":"<jats:p>Ageing results in the progressive loss of near vision, known as presbyopia, which impacts individuals and society. Existing corrective methods offer only partial compensation and do not restore dynamic focusing at varying distances. This work presents a closed-loop correction system for presbyopia, employing biopotential signals from the ciliary muscle and an artificial neural network to predict the eye\u2019s accommodative state in real time. Non-invasive contact lens electrodes collect biopotential data, which are preprocessed and classified using a multi-layer perceptron. The classifier output guides a control system that adjusts an external focus-tunable lens, enabling both accommodation and disaccommodation similar to a young eye. The system demonstrated an accuracy of 0.79, with F1-scores of 0.78 for prediction of accommodation and 0.77 for disaccommodation. Using the system in two presbyopic subjects, near visual acuity improved from 0.28 and 0.38 to 0.04 and \u22120.03 logMAR, while distance acuity remained stable. Despite challenges such as signal quality and individual variability, the findings demonstrate the feasibility of restoring near-natural accommodation in presbyopia using neuromuscular signals and adaptive lens control. Future research will focus on system validation, expanding the dataset, and pre-clinical testing in implantable devices.<\/jats:p>","DOI":"10.3390\/bioengineering12111228","type":"journal-article","created":{"date-parts":[[2025,11,10]],"date-time":"2025-11-10T13:51:08Z","timestamp":1762782668000},"page":"1228","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Real-Time Control of a Focus Tunable Lens for Presbyopia Correction Using Ciliary Muscle Biopotentials and Artificial Neural Networks"],"prefix":"10.3390","volume":"12","author":[{"given":"Bishesh","family":"Sigdel","sequence":"first","affiliation":[{"name":"Institute for Ophthalmic Research, University of Tuebingen, 72076 Tuebingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-6029-5280","authenticated-orcid":false,"given":"Sven","family":"Schumayer","sequence":"additional","affiliation":[{"name":"Institute for Ophthalmic Research, University of Tuebingen, 72076 Tuebingen, Germany"},{"name":"Faculty Mechanical and Medical Engineering (MME), Institute for Microsystems Technology (iMST), Furtwangen University, 78120 Furtwangen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sebastian","family":"Kaltenstadler","sequence":"additional","affiliation":[{"name":"Institute of Microelectronics, University of Ulm, 89081 Ulm, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Eberhart","family":"Zrenner","sequence":"additional","affiliation":[{"name":"Institute for Ophthalmic Research, University of Tuebingen, 72076 Tuebingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5017-619X","authenticated-orcid":false,"given":"Volker","family":"Bucher","sequence":"additional","affiliation":[{"name":"Faculty Mechanical and Medical Engineering (MME), Institute for Microsystems Technology (iMST), Furtwangen University, 78120 Furtwangen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Albrecht","family":"Rothermel","sequence":"additional","affiliation":[{"name":"Institute of Microelectronics, University of Ulm, 89081 Ulm, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7725-7961","authenticated-orcid":false,"given":"Torsten","family":"Stra\u00dfer","sequence":"additional","affiliation":[{"name":"Institute for Ophthalmic Research, University of Tuebingen, 72076 Tuebingen, Germany"},{"name":"University Eye Hospital Tuebingen, 72076 Tuebingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,11,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"207","DOI":"10.1111\/j.1444-0938.2008.00256.x","article-title":"The Eye in Focus: Accommodation and Presbyopia","volume":"91","author":"Charman","year":"2008","journal-title":"Clin. Exp. Optom."},{"key":"ref_2","first-page":"956","article-title":"Massive Increase in the Stiffness of the Human Lens Nucleus with Age: The Basis for Presbyopia?","volume":"10","author":"Heys","year":"2004","journal-title":"Mol. Vis."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1113\/jphysiol.1969.sp008739","article-title":"Elastic Constants of the Human Lens Capsule","volume":"201","author":"Fisher","year":"1969","journal-title":"J. Physiol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1492","DOI":"10.1016\/j.ophtha.2018.04.013","article-title":"Global Prevalence of Presbyopia and Vision Impairment from Uncorrected Presbyopia","volume":"125","author":"Fricke","year":"2018","journal-title":"Ophthalmology"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1010","DOI":"10.1001\/jama.1912.04270090254042","article-title":"Normal Values of Accommodation at All Ages","volume":"LIX","author":"Duane","year":"1912","journal-title":"JAMA"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/BF02720789","article-title":"Ueber die Accommodation des Auges","volume":"1","author":"Helmholtz","year":"1855","journal-title":"Graefes Arch. Clin. Exp. Ophthalmol."},{"key":"ref_7","first-page":"143","article-title":"Mechanism of Accommodation","volume":"Volume 1","author":"Southall","year":"1924","journal-title":"Helmholtz\u2019s Treatise on Physiological Optics (Trans. from the 3rd German ed.)"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"255","DOI":"10.1046\/j.1475-1313.1995.9500020e.x","article-title":"Accommodation and Presbyopia","volume":"15","author":"Atchison","year":"1995","journal-title":"Ophthalmic Physiol. Opt."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"437","DOI":"10.1016\/j.jcrs.2014.07.028","article-title":"Computer-Animated Model of Accommodation and Presbyopia","volume":"41","author":"Goldberg","year":"2015","journal-title":"J. Cataract Refract. Surg."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"e18437","DOI":"10.7717\/peerj.18437","article-title":"The Effect of Aging on the Ciliary Muscle and Its Potential Relationship with Presbyopia: A Literature Review","volume":"12","author":"Zuo","year":"2024","journal-title":"PeerJ"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1146\/annurev-vision-110623-080628","article-title":"Ocular Accommodation: The Autofocus Mechanism of the Human Eye","volume":"11","author":"Bharadwaj","year":"2025","journal-title":"Annu. Rev. Vis. Sci."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"646","DOI":"10.1038\/eye.1988.119","article-title":"The Mechanics of Accommodation in Relation to Presbyopia","volume":"2","author":"Fisher","year":"1988","journal-title":"Eye"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"379","DOI":"10.1016\/j.preteyeres.2004.11.001","article-title":"The Mechanism of Presbyopia","volume":"24","author":"Strenk","year":"2005","journal-title":"Prog. Retin. Eye Res."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"124","DOI":"10.1016\/j.preteyeres.2018.09.004","article-title":"Presbyopia: Effectiveness of Correction Strategies","volume":"68","author":"Wolffsohn","year":"2019","journal-title":"Prog. Retin. Eye Res."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Tabernero, J., Chirre, E., Hervella, L., Prieto, P., and Artal, P. (2016). The Accommodative Ciliary Muscle Function Is Preserved in Older Humans. Sci. Rep., 6.","DOI":"10.1038\/srep25551"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1111\/opo.12091","article-title":"Developments in the Correction of Presbyopia I: Spectacle and Contact Lenses","volume":"34","author":"Charman","year":"2014","journal-title":"Ophthalmic Physiol. Opt."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"397","DOI":"10.1111\/opo.12129","article-title":"Developments in the Correction of Presbyopia II: Surgical Approaches","volume":"34","author":"Charman","year":"2014","journal-title":"Ophthalmic Physiol. Opt."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"e001122","DOI":"10.1136\/bmjophth-2022-001122","article-title":"New Insights in Presbyopia: Impact of Correction Strategies","volume":"8","author":"Wolffsohn","year":"2023","journal-title":"BMJ Open Ophth."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"897","DOI":"10.1007\/s40266-024-01155-4","article-title":"Pilocarpine in the Treatment of Presbyopia: Progress, Issues, and Future Prospects","volume":"41","author":"Zhang","year":"2024","journal-title":"Drugs Aging"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"390","DOI":"10.1109\/TBME.2021.3094964","article-title":"Correcting Presbyopia With Autofocusing Liquid-Lens Eyeglasses","volume":"69","author":"Karkhanis","year":"2022","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"883","DOI":"10.1364\/BOE.543807","article-title":"Performance of Focus-Tunable Presbyopia Correction Lenses Operated Using Gaze-Tracking and LIDAR","volume":"16","author":"Agarwala","year":"2025","journal-title":"Biomed. Opt. Express"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"2440","DOI":"10.1364\/BOE.557747","article-title":"Dynamic Presbyopia Correction in the Macular Field of View by Using a Liquid Crystal Lens","volume":"16","author":"Galstian","year":"2025","journal-title":"Biomed. Opt. Express"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"488","DOI":"10.1113\/jphysiol.1957.sp005829","article-title":"The Reciprocal Actions of Accommodation and Convergence","volume":"137","author":"Fincham","year":"1957","journal-title":"J. Physiol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1069","DOI":"10.1016\/0042-6989(70)90083-0","article-title":"A Model of Accommodation","volume":"10","author":"Toates","year":"1970","journal-title":"Vis. Res."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"828","DOI":"10.1152\/physrev.1972.52.4.828","article-title":"Accommodation Function of the Human Eye","volume":"52","author":"Toates","year":"1972","journal-title":"Physiol. Rev."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"e206","DOI":"10.1016\/j.ophtha.2020.12.025","article-title":"Future Intraocular Lens Technologies","volume":"128","author":"Dick","year":"2021","journal-title":"Ophthalmology"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"116","DOI":"10.1007\/BF00682518","article-title":"Aktionspotentiale des M. ciliaris beim Menschen","volume":"157","author":"Schubert","year":"1955","journal-title":"Graefes. Arch. Clin. Exp. Ophthalmol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"592","DOI":"10.1001\/archopht.1958.00940080612007","article-title":"The Electrical Response of the Human Eye in Far-to-Near Accommodation","volume":"60","author":"Alpern","year":"1958","journal-title":"Arch. Ophthalmol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"231","DOI":"10.1016\/0002-9394(58)90802-X","article-title":"The Electric Activity of the Eye During Accommodation","volume":"46","author":"Jacobson","year":"1958","journal-title":"Am. J. Ophthalmol."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"323","DOI":"10.1159\/000304372","article-title":"The Action Potential of the Ciliary Muscle","volume":"144","author":"Hagiwara","year":"1962","journal-title":"Ophthalmologica"},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Schumayer, S., Sigdel, B., Jarboui, M.A., Zrenner, E., Bucher, V., Stra\u00dfer, T., and Wagner, S. (2025). Non-Invasive Measuring of Biopotentials of the Ciliary Muscle during Accommodation in Emmetropes. Sci. Rep., 15.","DOI":"10.1038\/s41598-025-04165-3"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Schumayer, S., Simon, N., Sittkus, B., Wagner, S., Bucher, V., and Strasser, T. (2022). Novel Three-Dimensional and Biocompatible Lift-Off Method for Selective Metallization of a Scleral Contact Lens Electrode for Biopotential Detection. Front. Med. Technol., 4.","DOI":"10.3389\/fmedt.2022.920384"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"5100","DOI":"10.1364\/BOE.9.005100","article-title":"Ciliary Muscle Thickness Profiles Derived from Optical Coherence Tomography Images","volume":"9","author":"Wagner","year":"2018","journal-title":"Biomed. Opt. Express"},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Kaltenstadler, S., Sigdel, B., Schumayer, S., Steinhoff, R., Stra\u00dfer, T., and Rothermel, A. (2024, January 15\u201319). An Implantable Ciliary Muscle LFP Recording and Transmitting System. Proceedings of the 2024 46th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Orlando, FL, USA.","DOI":"10.1109\/EMBC53108.2024.10781543"},{"key":"ref_35","unstructured":"Schumayer, S., Sigdel, B., Nikolaidou, A., Wolfram, L., Wagner, S., Zrenner, E., Bucher, V., and Stra\u00dfer, T. (2025, January 25\u201328). Preserved Ciliary Muscle Biopotentials Enable Artificial Lens Control and near Vision Recovery in Long-Term Presbyopia. Proceedings of the 62nd Annual Symposium of the International Society for Clinical Electrophysiology of Vision (ISCEV 2025), Utrecht, The Netherlands."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"631","DOI":"10.1097\/00006324-197809000-00005","article-title":"Accommodation Dynamics I. Range Nonlinearity","volume":"55","author":"Shirachi","year":"1978","journal-title":"Am. J. Optom. Physiol. Opt."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Wang, Z., Yan, W., and Oates, T. (2017, January 14\u201319). Time Series Classification from Scratch with Deep Neural Networks: A Strong Baseline. Proceedings of the 2017 International Joint Conference on Neural Networks (IJCNN), Anchorage, AK, USA.","DOI":"10.1109\/IJCNN.2017.7966039"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"420","DOI":"10.1007\/s42979-021-00815-1","article-title":"Deep Learning: A Comprehensive Overview on Techniques, Taxonomy, Applications and Research Directions","volume":"2","author":"Sarker","year":"2021","journal-title":"SN Comput. Sci."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"917","DOI":"10.1007\/s10618-019-00619-1","article-title":"Deep Learning for Time Series Classification: A Review","volume":"33","author":"Forestier","year":"2019","journal-title":"Data Min. Knowl. Discov."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"915","DOI":"10.1016\/j.asoc.2017.09.027","article-title":"Real-Time Human Activity Recognition from Accelerometer Data Using Convolutional Neural Networks","volume":"62","author":"Ignatov","year":"2018","journal-title":"Appl. Soft Comput."},{"key":"ref_41","unstructured":"Goodfellow, I., Courville, A., and Bengio, Y. (2016). Deep Learning, The MIT Press."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1373","DOI":"10.1007\/s00530-020-00728-8","article-title":"Myocardial Infarction Detection Based on Deep Neural Network on Imbalanced Data","volume":"28","author":"Hammad","year":"2022","journal-title":"Multimed. Syst."},{"key":"ref_43","first-page":"27","article-title":"Evaluation Measures for Models Assessment over Imbalanced Data Sets","volume":"3","author":"Bekkar","year":"2013","journal-title":"J. Inf. Eng. App."},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Jeni, L.A., Cohn, J.F., and De La Torre, F. (2013, January 2\u20135). Facing Imbalanced Data--Recommendations for the Use of Performance Metrics. Proceedings of the 2013 Humaine Association Conference on Affective Computing and Intelligent Interaction, Geneva, Switzerland.","DOI":"10.1109\/ACII.2013.47"},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Chen, T., and Guestrin, C. (2016, January 13\u201317). XGBoost: A Scalable Tree Boosting System. Proceedings of the Proceedings of the 22nd ACM SIGKDD International Conference on Knowledge Discovery and Data Mining, San Francisco, CA, USA.","DOI":"10.1145\/2939672.2939785"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"107741","DOI":"10.1016\/j.exer.2019.107741","article-title":"Prolonged Nearwork Affects the Ciliary Muscle Morphology","volume":"186","author":"Wagner","year":"2019","journal-title":"Exp. Eye. Res."},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Faouzi, J. (2024). Time Series Classification: A Review of Algorithms and Implementations. Time Series Analysis\u2014Recent Advances, New Perspectives and Applications, IntechOpen.","DOI":"10.5772\/intechopen.1004810"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"4","DOI":"10.1167\/jov.22.9.4","article-title":"Seeing the Future: Predictive Control in Neural Models of Ocular Accommodation","volume":"22","author":"Read","year":"2022","journal-title":"J. Vis."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"476","DOI":"10.1111\/opo.12234","article-title":"Microfluctuations in Accommodation: An Update on Their Characteristics and Possible Role","volume":"35","author":"Charman","year":"2015","journal-title":"Ophthalmic Physiol. Opt."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"12","DOI":"10.1167\/iovs.64.2.12","article-title":"Lens Thickness Microfluctuations in Young and Prepresbyopic Adults During Steady-State Accommodation","volume":"64","author":"Rohman","year":"2023","journal-title":"Investig. Ophthalmol. Vis. Sci."},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Kazanskiy, N.L., Khonina, S.N., and Butt, M.A. (2023). Smart Contact Lenses\u2014A Step towards Non-Invasive Continuous Eye Health Monitoring. Biosensors, 13.","DOI":"10.3390\/bios13100933"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"154823","DOI":"10.1016\/j.cej.2024.154823","article-title":"Smart Contact Lenses: From Rational Design Strategies to Wearable Health Monitoring","volume":"497","author":"Han","year":"2024","journal-title":"Chem. Eng. J."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"6817","DOI":"10.1021\/acsnano.3c12072","article-title":"Smart Contact Lenses for Healthcare Monitoring and Therapy","volume":"18","author":"Liu","year":"2024","journal-title":"ACS Nano"},{"key":"ref_54","doi-asserted-by":"crossref","unstructured":"Schumayer, S., Zahrani, E.G., Azarhoushang, B., Bucher, V., and Stra\u00dfer, T. (2025). Design and In Vivo Evaluation of an Intraocular Electrode for Ciliary Muscle Biopotential Measurement in a Non-Human Primate Model of Human Accommodation. Biosensors, 15.","DOI":"10.3390\/bios15040247"},{"key":"ref_55","unstructured":"Clouse, M.M. (2017). Recording and Processing of Tissue-Specific Ocular Electrical Biosignals for Applications in Biomedical Devices. [Ph.D. Thesis, University of T\u00fcbingen]."}],"container-title":["Bioengineering"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2306-5354\/12\/11\/1228\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,11,12]],"date-time":"2025-11-12T05:11:59Z","timestamp":1762924319000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2306-5354\/12\/11\/1228"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,11,10]]},"references-count":55,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2025,11]]}},"alternative-id":["bioengineering12111228"],"URL":"https:\/\/doi.org\/10.3390\/bioengineering12111228","relation":{},"ISSN":["2306-5354"],"issn-type":[{"type":"electronic","value":"2306-5354"}],"subject":[],"published":{"date-parts":[[2025,11,10]]}}}