## 1 Introduction  
Presbyopia is an age-related condition that prevents focusing on near objects; it is a natural part of the aging process and begins to develop around age 40 [1]. Progressive power lenses (PPLs) are a popular solution for presbyopes, as they provide a gradual transition of spherical power between distance and near vision, allowing wearers to see clearly at all distances by changing their gaze direction [2]. Due to the power variation along the vertical main meridian, usually an umbilical curve, unwanted astigmatic and spherical power variations appear in the lateral areas of the lens and affect the quality of vision [3; 4]. Some proposed methods to evaluate the quality of vision with PPLs are based on the representation of theoretical power distribution maps obtained with lens mappers [5; 6] or calculated using exact ray tracking to obtain user-perceived power distribution maps [7; 8]. They are based on geometrical magnitude calculations that estimate the theoretical fields of view [5; 6; 9]. Although theoretical representations could be useful to characterize PPLs, the quality of vision varies depending on the subjective visual perception of the user. In order to gain a better understanding of this topic, several studies have been carried out to evaluate the quality of vision with PPLs using different methods such as satisfaction questionnaires [10; 11; 12; 13], contrast sensitivity [14], reading performance [11; 15], skew distortion [16], or high contrast visual acuity (VA) [12; 17; 18; 19]. High-contrast VA is one of the main ways to assess the quality of vision with PPLs. VA refers to the ability to discern object details subtending a certain angle and is commonly employed in clinical practice to measure vision quality. It is also the standard measure to assess the quality of an optical correction [1]. The measurement of VA has been extensively used to evaluate the impact of lateral refractive errors in PPLs on visual performance. [PERSON] et al. [17] evaluated differences in VA with 2 different PPLs and reported worse VA values when viewing through the lateral regions of the lens in comparison with the central region. [PERSON] et al. [19] also evaluated the effect of off-axis refractive errors in a PPL and showed a reduction in VA at off-axis gaze directions in comparison with centered gaze directions. However, these studies have not found significant differences in VA scores between different types of PPLs. This could be because the VA score does not consider other factors that impact visual perception, such as the time needed to recognize the optotypes. For this reason, this work proposes the assessment of the visual quality provided by PPLs by means of parameters such as recognition speed or the number of eye fixations while recognizing the optotypes. Video-based ETs allow the monitoring and recording of gaze positions by sending infrared light to the subject's eye and recording with a camera the light reflected from it [20; 21]. The bright pupil and the corneal reflections are processed using advanced image-processing software to obtain the instantaneous gaze direction with high accuracy and to calculate eye movements as saccades and fixations [21; 22; 23]. Thanks to these systems, it is possible to study the influence of factors such as text characteristics [24] or blur on eye movements [25]. In the field of PPLs, this technology has been widely used to study how lateral refractive errors of PPLs affect eye fixations. [PERSON] et al. [26; 27] analyzed differences in eye fixations when reading with PPLs vs. single-vision lenses. [PERSON] et al. [28] studied differences in eye fixations while reading on a monitor screen with two different PPL designs. [PERSON] et al. [29] studied differences in eye fixations while driving between PPL users in comparison with non-PPL users. All of them demonstrated that lateral unwanted refractive errors of PPLs affect eye fixation characteristics.