{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T17:48:16Z","timestamp":1777484896513,"version":"3.51.4"},"reference-count":37,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2020,9,1]],"date-time":"2020-09-01T00:00:00Z","timestamp":1598918400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Fixation identification is an essential task in the extraction of relevant information from gaze patterns; various algorithms are used in the identification process. However, the thresholds used in the algorithms greatly affect their sensitivity. Moreover, the application of these algorithm to eye-tracking technologies integrated into head-mounted displays, where the subject\u2019s head position is unrestricted, is still an open issue. Therefore, the adaptation of eye-tracking algorithms and their thresholds to immersive virtual reality frameworks needs to be validated. This study presents the development of a dispersion-threshold identification algorithm applied to data obtained from an eye-tracking system integrated into a head-mounted display. Rules-based criteria are proposed to calibrate the thresholds of the algorithm through different features, such as number of fixations and the percentage of points which belong to a fixation. The results show that distance-dispersion thresholds between 1\u20131.6\u00b0 and time windows between 0.25\u20130.4 s are the acceptable range parameters, with 1\u00b0 and 0.25 s being the optimum. The work presents a calibrated algorithm to be applied in future experiments with eye-tracking integrated into head-mounted displays and guidelines for calibrating fixation identification algorithms<\/jats:p>","DOI":"10.3390\/s20174956","type":"journal-article","created":{"date-parts":[[2020,9,1]],"date-time":"2020-09-01T14:21:10Z","timestamp":1598970070000},"page":"4956","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":69,"title":["Development and Calibration of an Eye-Tracking Fixation Identification Algorithm for Immersive Virtual Reality"],"prefix":"10.3390","volume":"20","author":[{"given":"Jose","family":"Llanes-Jurado","sequence":"first","affiliation":[{"name":"Instituto de Investigaci\u00f3n e Innovaci\u00f3n en Bioingenier\u00eda (i3B), Universitat Polit\u00e8cnica de Val\u00e8ncia, 46022 Valencia, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1271-2892","authenticated-orcid":false,"given":"Javier","family":"Mar\u00edn-Morales","sequence":"additional","affiliation":[{"name":"Instituto de Investigaci\u00f3n e Innovaci\u00f3n en Bioingenier\u00eda (i3B), Universitat Polit\u00e8cnica de Val\u00e8ncia, 46022 Valencia, Spain"}]},{"given":"Jaime","family":"Guixeres","sequence":"additional","affiliation":[{"name":"Instituto de Investigaci\u00f3n e Innovaci\u00f3n en Bioingenier\u00eda (i3B), Universitat Polit\u00e8cnica de Val\u00e8ncia, 46022 Valencia, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9207-0636","authenticated-orcid":false,"given":"Mariano","family":"Alca\u00f1iz","sequence":"additional","affiliation":[{"name":"Instituto de Investigaci\u00f3n e Innovaci\u00f3n en Bioingenier\u00eda (i3B), Universitat Polit\u00e8cnica de Val\u00e8ncia, 46022 Valencia, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2020,9,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2086","DOI":"10.3389\/fpsyg.2018.02086","article-title":"The Past, Present, and Future of Virtual and Augmented Reality Research: A Network and Cluster Analysis of the Literature","volume":"9","author":"Cipresso","year":"2014","journal-title":"Front. Psyc."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"959","DOI":"10.3389\/fpsyg.2017.00959","article-title":"A Novel Integrating Virtual Reality Approach for the Assessment of the Attachment Behavioral System","volume":"8","author":"Pravettoni","year":"2017","journal-title":"Front. Psyc."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Vince, J. (2004). Introduction to Virtual Reality, Springer Verl.. [2nd ed.].","DOI":"10.1007\/978-0-85729-386-2"},{"key":"ref_4","first-page":"34","article-title":"Methodological bases for a new platform for the measurement of human behaviour in virtual environments","volume":"92","author":"Guixeres","year":"2017","journal-title":"DYNA"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"208","DOI":"10.1093\/iwc\/iwz018","article-title":"Navigation comparison between a real and a virtual museum: Time-dependent differences using a head mounted display","volume":"31","author":"Llinares","year":"2019","journal-title":"Interac. Comput."},{"key":"ref_6","first-page":"141","article-title":"The EMMA Project: Emotions as a Determinant of Presence","volume":"1","author":"Botella","year":"2003","journal-title":"PsychNology J."},{"key":"ref_7","first-page":"1","article-title":"The EMMA Project: Emotions as a Determinant of Presence","volume":"14","author":"Greco","year":"2019","journal-title":"PLoS ONE"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"365","DOI":"10.1016\/j.ijpsycho.2011.12.003","article-title":"Cortical correlate of spatial presence in 2D and 3D interactive virtual reality: An EEG study","volume":"83","author":"Kober","year":"2012","journal-title":"Int. J. Psychophys."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"68","DOI":"10.1186\/s12984-016-0174-1","article-title":"Feasibility of a walking virtual reality system for rehabilitation: Objective and subjective parameters","volume":"13","author":"Borrego","year":"2016","journal-title":"J. Neuroeng. Rehabil."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1584","DOI":"10.1016\/j.eswa.2013.08.055","article-title":"Assessment of the influence of navigation control and screen size on the sense of presence in virtual reality using EEG","volume":"41","author":"Clemente","year":"2014","journal-title":"Expert Sys. Appl."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1089\/g4h.2017.0114","article-title":"Comparison of Oculus Rift and HTC Vive: Feasibility for Virtual Reality-Based Exploration, Navigation, Exergaming, and Rehabilitation","volume":"7","author":"Borrego","year":"2018","journal-title":"Games Health J."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1515","DOI":"10.1007\/s10639-017-9676-0","article-title":"A review of the use of virtual reality head-mounted displays in education and training","volume":"23","author":"Jensen","year":"2017","journal-title":"Educ. Inf. Technol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"109","DOI":"10.1016\/j.jbiomech.2019.109379","article-title":"A quantitative method for evaluation of 6 degree of freedom virtual reality systems","volume":"97","author":"Jost","year":"2019","journal-title":"J. Biomech."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"513","DOI":"10.1177\/0047239518824862","article-title":"Effect of Degrees of Freedom on the Sense of Presence Generated by Virtual Reality (VR) Head-Mounted Display Systems: A Case Study on the Use of VR in Early Design Studios","volume":"47","author":"Chandrasekera","year":"2019","journal-title":"J. Educ. Technol. Syst."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"B\u0103lan, O., Moise, G., Moldoveanu, A., Leordeanu, M., and Moldoveanu, F. (2020). An Investigation of Various Machine and Deep Learning Techniques Applied in Automatic Fear Level Detection and Acrophobia Virtual Therapy. Sensors, 20.","DOI":"10.3390\/s20020496"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"704","DOI":"10.1016\/j.cpr.2012.09.004","article-title":"Eye tracking of attention in the affective disorders: A meta-analytic review and synthesis","volume":"32","author":"Armstrong","year":"2012","journal-title":"Clinical Psychol. Rev."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"372","DOI":"10.1037\/0033-2909.124.3.372","article-title":"Eye movements in reading and information processing: 20 years of research","volume":"124","author":"Rayner","year":"1998","journal-title":"Psychol. Bulletin"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"307","DOI":"10.1037\/0278-7393.18.2.307","article-title":"Memory for position and identity across eye movements","volume":"18","author":"Irwin","year":"1992","journal-title":"J. Exp. Psychol. Learn. Mem. Cogn."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Tanriverdi, V., and Jacob, R.J.K. (2000). Interacting with Eye Movements in Virtual Environments. Assoc. Comput. Machin., 265\u2013272.","DOI":"10.1145\/332040.332443"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"426","DOI":"10.3389\/fnbeh.2014.00426","article-title":"Forced-choice decision-making in modified trolley dilemma situations: A virtual reality and eye tracking study","volume":"8","author":"Skulmowski","year":"2014","journal-title":"Front. Behav. Neurosci."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"305","DOI":"10.3389\/fnins.2018.00305","article-title":"The Immersive Virtual Reality Lab: Possibilities for Remote Experimental Manipulations of Autonomic Activity on a Large Scale","volume":"12","author":"Juvrud","year":"2018","journal-title":"Front. Neurosci."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"3","DOI":"10.16910\/jemr.12.1.3","article-title":"Eye Tracking in Virtual Reality","volume":"12","author":"Clay","year":"2019","journal-title":"J. Eye Mov. Res."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"180502","DOI":"10.1098\/rsos.180502","article-title":"Is the eye-movement field confused about fixations and saccades? A survey among 124 researchers","volume":"5","author":"Hessels","year":"2018","journal-title":"R. Soc. Open Sci."},{"key":"ref_24","first-page":"1","article-title":"Real-time recording and classification of eye movements in an immersive virtual environment","volume":"13","author":"Cooper","year":"2013","journal-title":"J. Vis."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1","DOI":"10.16910\/jemr.8.5.1","article-title":"Eye Tracking in the Wild: The Good, the Bad and the Ugly","volume":"8","author":"Lappi","year":"2015","journal-title":"J. Eye Mov. Res."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Duchowski, A.T., Medlin, E., Gramopadhye, A., Melloy, B., and Nair, S. (2001). Binocular Eye Tracking in VR for Visual Inspection Training. Assoc. Comput. Mach., 1\u20138.","DOI":"10.1145\/505008.505010"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Lim, J.Z., Mountstephens, J., and Teo, J. (2020). Emotion Recognition Using Eye-Tracking: Taxonomy, Review and Current Challenges. Sensors, 20.","DOI":"10.3390\/s20082384"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1016\/S0165-0270(03)00151-1","article-title":"Defining the temporal threshold for ocular fixation in free-viewing visuocognitive tasks","volume":"128","author":"Manor","year":"2003","journal-title":"J. Neurosci. Methods"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1145\/355017.355028","article-title":"Identifying fixations and saccades in eye-tracking protocols","volume":"10","author":"Salvucci","year":"2000","journal-title":"Proc. Eye Track. Res. Appli. (ETRA) Symp."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"573","DOI":"10.3758\/BF03195486","article-title":"3-D eye movement analysis","volume":"34","author":"Duchowski","year":"2002","journal-title":"Behav. Res. Methods Instrum. Comput. J. Psychon. Soc. Inc."},{"key":"ref_31","unstructured":"Duchowski, A. (2007). Eye Tracking Methodology: Theory and Practice, Springer Publ. Co. Inc.. [2nd ed.]."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Bobi\u0107, V., and Graovac, S. (2016). Development, implementation and evaluation of new eye tracking methodology. Telecommun. Forum (TELFOR), 1\u20134.","DOI":"10.1109\/TELFOR.2016.7818800"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Sidenmark, L., and Lundstr\u00f6m, A. (2019). Gaze behaviour on interacted objects during hand interaction in virtual reality for eye tracking calibration. Symp. Eye Track. Res. Appl., 1\u20139.","DOI":"10.1145\/3314111.3319815"},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Al Ghamdi, N., and Alhalabi, W. (2019). Fixation Detection with Ray-casting in Immersive Virtual Reality. Int. J. Adv. Comput. Sci. Appli., 10.","DOI":"10.14569\/IJACSA.2019.0100710"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"881","DOI":"10.3758\/APP.71.4.881","article-title":"Fixation identification: The optimum threshold for a dispersion algorithm","volume":"71","author":"Blignaut","year":"2009","journal-title":"Atten. Percept. Psychophys."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Shic, F., Scassellati, B., and Chawarska, K. (2008). The Incomplete Fixation Measure. Proc. Eye Track. Res. Appli. (ETRA) Symp., 111\u2013114.","DOI":"10.1145\/1344471.1344500"},{"key":"ref_37","unstructured":"Vive, H. (2020, September 01). Vive Pro Eye. Available online: https:\/\/www.vive.com\/us\/."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/17\/4956\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T10:05:40Z","timestamp":1760177140000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/17\/4956"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,9,1]]},"references-count":37,"journal-issue":{"issue":"17","published-online":{"date-parts":[[2020,9]]}},"alternative-id":["s20174956"],"URL":"https:\/\/doi.org\/10.3390\/s20174956","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,9,1]]}}}