A New Algorithm for Identifying Saccadic Movements in Eye-Tracking Studies
Saccades—rapid, coordinated eye movements—play a crucial role in vision, especially for wearers of progressive power lenses (PPLs). These lenses allow users to transition between different focal zones, but how effectively they do so depends on how the eyes move. However, traditional methods for tracking saccades often struggle with accuracy, particularly in real-world conditions using wearable eye-tracking devices. This limitation can lead to incomplete insights into lens performance and wearer experience.
A new algorithm aims to improve saccade detection and analysis, addressing these gaps. By comparing this approach to the widely used Tobii I-VT fixation filter, researchers evaluated how different PPL designs influence saccade characteristics during distance and near reading tasks. These findings have important implications for optical labs and eye care professionals (ECPs) looking to optimize progressive lens design and improve wearer adaptation.
Figure 1. Gaze samples with a velocity below the threshold corresponds to fixations (blue) and above to saccades (green).
Why saccade tracking matters in progressive lenses
Progressive lenses are designed to provide smooth vision at all distances, but wearers don’t always use them as intended. Factors like peripheral distortions, adaptation challenges, and individual viewing habits can all impact gaze shifts and visual comfort. Analyzing saccadic movements offers valuable insights that can:
Improve lens designs to enhance comfort and adaptation
Help eye care professionals (ECPs) guide patients toward the right lens choice
Reduce wearer discomfort caused by inefficient visual transitions
However, traditional velocity-based algorithms often misclassify saccades in wearable eye-tracking data due to lower sampling rates and fragmented movements. This study introduces a new method to improve classification and analysis, providing a more reliable way to track real-world eye movements.
Figure 2. Cylinder power distribution maps of the PPLs tested in this study.
How the study was conducted
Participants and study design
This double-masked, longitudinal study included 28 PPL wearers (17 men, 11 women) aged 46 to 64. All participants had normal vision and no conditions affecting their eye movements.Each subject was fitted with three different free-form PPL designs:
PPL-Distance (PPL-D) – optimized for a wider distance vision area
PPL-Near (PPL-N) – designed for a larger near-vision zone
PPL-Balance (PPL-B) – a symmetrical distribution for general use
Eye movements were recorded using Tobii Pro Glasses 3 while participants performed distance and near reading tasks. The collected data was processed using both the existing Tobii I-VT fixation filter and the newly developed algorithm.
Figure 3. Scheme for the evaluation of reading speed at distance vision (A) and near vision (B).
How the new algorithm improves saccade tracking
The new algorithm addresses key weaknesses in traditional velocity-based tracking by:
Maintaining reliable fixation classification from the original Tobii I-VT filter
Reclassifying fragmented movements between fixations as single saccades
Refining saccade duration calculations by summing all gaze data between fixations
Improving saccade amplitude measurements for greater accuracy
Filtering out noise and misclassifications using an outlier detection algorithm
By correcting misclassifications and integrating fragmented movements, this method provides a clearer picture of how wearers interact with different lens zones, particularly in lower-sampling wearable eye-tracking systems.
Figure 4. Saccade amplitude (θ) calculation from one fixation (Fn) to the next (Fn+1).
Key findings: How PPL design affects saccadic movements
Figure 5. Example of gaze data where saccade is divided into several parts using the original algorithm (A), and when applying the new algorithm than unifies the saccade and data loss into a single movement (B).
Distance reading task
With the new algorithm, the number of saccades better aligned with the number of fixations, showing one fewer saccade than fixations per trial. Compared to the original algorithm:
Saccade count decreased by 26% in PPL-D, 26% in PPL-B, and 25% in PPL-N
Saccade time increased by 22% in PPL-D, 24% in PPL-B, and 21% in PPL-N
Significant differences were found in saccade count (p=0.04) and amplitude (p=0.04) between designs
PPL-D showed fewer saccades and greater saccade amplitude compared to PPL-N
Near reading task
Similar trends were observed in near reading:
Saccade count decreased by 33% in PPL-N, 34% in PPL-B, and 36% in PPL-D
Saccade time increased by 32% in PPL-N, 34% in PPL-B, and 41% in PPL-D
Significant differences were found in saccade count (p<0.001), saccade time (p<0.001), and saccade amplitude (p=0.002)
PPL-N showed the lowest saccade count and saccade time, but the highest saccade amplitude
These findings suggest that PPL-D is more efficient for distance vision tasks, while PPL-N facilitates smoother near reading movements, influencing wearer comfort and adaptation.
Figure 6. Mean values and 95% confidence intervals for fixation and saccade count (A), saccade time (B), and mean saccade amplitude (C) for each of the PPL designs. Denotes statistically significant differences between PPL groups.
Implications for optical labs and ECPs
For optical labs
Improve progressive lens designs by considering how power distribution affects saccades
Optimize lens transitions to enhance comfort and reduce adaptation time
Develop better quality control methods for assessing real-world lens performance
For ECPs
Offer better lens recommendations based on patients’ visual habits
Help patients adapt to new prescriptions by understanding their natural eye movement patterns
Educate wearers on lens selection for tasks like reading, computer use, or driving
Advancing eye-tracking analysis in lens research
This study introduces an improved algorithm for detecting and classifying saccadic movements in wearable eye-tracking data. By refining gaze data analysis, researchers provide new insights into how different PPL designs influence eye movements in both distance and near vision tasks.
These findings can help optimize progressive lens performance, improve wearer comfort, and support ECPs in making more informed lens recommendations.
Download the Full Poster
Explore the development of a new algorithm for more accurate saccade detection using wearable eye-tracking. This poster outlines the study’s methodology, comparison to traditional tracking methods, and key findings on how different progressive lens designs influence eye movements. Learn how these insights can support better lens design, wearer adaptation, and real-world performance analysis.
Pablo Concepcion-Grande holds a degree in Optics and Optometry, a master’s in optometry and Vision, and a PhD in Optics, Optometry, and Vision from the Complutense University of Madrid. Since 2015, he has been working as a Research Scientist specializing in optical research, specifically in spectacle optics and contributing to the development of innovative ophthalmic lenses and conducting clinical research in the field of ophthalmic optics. His PhD thesis investigated how eye movement patterns are influenced by progressive power lenses using eye-tracking technology.
Acceptez-vous nos cookies et nos politiques de confidentialité ?
Votre vie privée est importante pour nous. Par conséquent, nous vous informons que nous utilisons nos propres cookies et ceux de tiers pour effectuer une analyse de l'utilisation et de la mesure de notre site Web afin de personnaliser le contenu, ainsi que de fournir des fonctionnalités aux réseaux sociaux ou d'analyser notre trafic. Pour continuer acceptez ou modifiez la configuration de nos cookies.
Cookies are very small text files that are stored on your computer when you visit a website. We use cookies for a variety of purposes and to enhance your online experience on our website (for example, to remember your account login details).
You can change your preferences and decline certain types of cookies to be stored on your computer while browsing our website. You can also remove any cookies already stored on your computer, but keep in mind that deleting cookies may prevent you from using parts of our website.
Strictly necessary cookies
These cookies are essential to provide you with services available through our website and to enable you to use certain features of our website.
Without these cookies, we cannot provide you certain services on our website.
Preference or customization cookies
These cookies are used to provide you with a more personalized experience on our website and to remember choices you make when you use our website.
For example, we may use functionality cookies to remember your language preferences or remember your login details.
Analysis or measurement cookies
These cookies are used to collect information to analyze the traffic to our website and how visitors are using our website.
For example, these cookies may track things such as how long you spend on the website or the pages you visit which helps us to understand how we can improve our website site for you.
The information collected through these analysis or measurement cookies do not identify any individual visitor.
Cookies Policy
This cookie notice provides information about the types of cookies INDIZEN OPTICAL TECHNOLOGIES SL uses and why we use them. Your access to, and use of, the Site http://www.iotlenses.com. We inform you about our cookies Policy.
WEBSITE OWNER
Thank you for accessing the Site http://www.iotlenses.com which is owned and operated by:
Website Owner: INDIZEN OPTICAL TECHNOLOGIES SL - CIF B84465921- IOT Postal Address: C/Suero de Quiñones 34-36. 28002, Madrid (Madrid), España Contact: Phone: 91 833 3786 - Email: proteccion_datos@iot.es Activity: Innovation in lenses
WHAT ARE COOKIES?
Cookies are small files that web pages, online stores, intranets, online platforms or similar, store in the browser of the user who visits them and are necessary to provide innumerable advantages to web browsing in the provision of interactive services.
The following information on the possible types of cookies helps to better understand the functions they make possible:
Session cookies: these are temporary cookies that remain in the cookie space of your computer until you close the browser, so that none is recorded on the user's disk. The information obtained through these cookies serves to enable operational management with each of the users who are simultaneously accessing the web.
Persistent cookies: these are cookies that remain stored in the cookie space of your computer once the browser is closed, and that you will consult this web page again the next time you access it to remember information that facilitates navigation (directly access the service without need to do the login process) or the provision of a commercial service (offer those products or services related to previous visits).
The cookies exchanged when browsing a web page can be:
First-party or own cookies: these are cookies generated by the website that is being visited.
Third-party cookies: these are cookies that are received when browsing that web page, but that have been generated by a third service that is hosted on it. An example may be the cookie used by an advertisement or advertising banner found on the web page we visit. Another may be the cookie used by a visitor counter hired by the website we visit.
Cookies can be used to:
Technical purposes: they are also called "strictly necessary". They allow the user to navigate through a web page, platform or application and use the different options or services that exist in it, such as, for example, controlling traffic and data communication, identifying the session, access parts of restricted access, remember the elements that make up an order, carry out the process of purchasing an order, make the request for registration or participation in an event, use security elements while browsing, store content for the dissemination of videos or sound or share content through social networks .
Personalization: they make it possible for each user to configure aspects such as the language in which they want to view the web page, display formats, etc.
Analysis or performance: they allow us to measure the number of visits and navigation criteria of different areas of the web, application or platform and allow us to elaborate navigation profiles of the users of said sites, applications and platforms, in order to introduce improvements based on the analysis of the use data collected by users of the service.
Advertising: they allow the implementation of efficiency parameters in the advertising offered on the web pages.
Behavioral advertising: they allow the implementation of efficiency parameters in the advertising offered on the web pages, based on information about the behavior of the users obtained through the continuous observation of their browsing habits, which allows the development of a specific profile. {co to display advertising based on it.
WHICH COOKIES DO WE USE?
ANALYTICS COOKIES - Google Tag Manager
Description:
These allow us to recognize and count the number of users of our Sites and understand how such users navigate through our Sites.
Use:
We use Google Analytics, and you can see below for how to control the use of cookies by Google Analytics.
This helps to improve how our Sites works, for example, by ensuring that users can find what they are looking for easily.
ANALYTICS COOKIES - Hubspot
Description: HubSpot cookies are used to track visitors and understand their behavior on our Sites. This helps us to better engage with our users and improve their experience.
Use: We use HubSpot to analyze user interactions with our Sites and to optimize our marketing efforts. HubSpot cookies allow us to:
Track visitor activity and behavior on our Sites.
Identify repeat visitors and their preferences.
Enhance the user experience by providing personalized content.
Measure the effectiveness of our marketing campaigns.
SOCIAL NETWORK
Description:
Social network cookies to register are used to link the web profile in the aforementioned social network.
Use:
You can use this button to redirect to the profile of your account IOT on LinkedIn, YouTube, Instagram and Facebook.
THIRD PARTY COOKIE
Additionally, IOT has a presence in portals and third-party services for which, if you want to know the privacy conditions and use of cookies, you should consult the policies provided by them:
IOT offers information about its Cookies Policy at the bottom of the website.
With this information you can carry out the following actions:
Accept cookies: this notice will not be displayed again when you enter the website again.
Reject cookies: this notice will not be displayed again when entering the website again.
Cookie settings: you can obtain more information about the cookies we use, read the Cookies Policy of IOT and modify the configuration to block cookies from IOT at any time. In the case of blocking cookies, the functionality of the Web may be reduced.
HOW TO DISABLE COOKIES?
Non-mandatory cookies may be disabled by adjusting the settings of the Website.
Said settings are located at the bottom of the Website. Furthermore, all browsers may be modified to disable the cookies configuration.
This is why most browsers offer the possibility to administer cookies: in order to allow for a more accurate control of privacy. Said settings may be located in the “options” or “preferences” section of the browser’s menu.
Find below links to disable cookies on each browser:
You may configure privacy with a six-position cursor which enables you to control the cookies which will be installed: Block all cookies, High, Medium High, Medium (default level), Low and Accept all cookies.
Select the “Preferences” option in the settings menu.
Open the privacy tab.
Select the desired option in the “block cookies” section. ()
Remember that you may not be able to use certain functions of the Website after disabling cookies.
If you do not wish to be tracked by cookies, Google has developed a complement which may be installed on your browser. Find it here: http://goo.gl/up4ND.
COOKIES ON MOBILE DEVICES?
The holder of the Website http://www.iotlenses.com also uses cookies and other storage means on mobile devices.
Cookies which are not mandatory to navigate this Website http://www.iotlenses.com may be disabled by entering “Set cookies on the button below to the right”.
These settings are located at the bottom of the Website http://www.iotlenses.com. Furthermore, as in the case of computer browsers, it is possible to disable or eliminate cookies by changing the options or settings in mobile device browsers.
If you wish to change the privacy options, follow the instructions of the developer of your mobile device browser. Find below a few examples of links you may use to modify privacy options on your mobile device.
This Website http://www.iotlenses.com does not install cookies on the Users’ devices prior to acceptance thereof by the Users.
We hereby inform you that if you reject the installation of cookies or disable these in your browser settings, certain services may not be available to you and therefore you may not be able to gain access to certain services and/or make full use of this Website http://www.iotlenses.com.