Sampling rate influences saccade detection in mobile eye tracking of a reading task

The purpose of this study was to compare saccade detection characteristics in two mobile eye trackers with different sampling rates in a natural task. Gaze data of 11 participants were recorded in one 60 Hz and one 120 Hz mobile eye tracker and compared directly to the saccades detected by a 1000 HZ stationary tracker while a reading task was performed. Saccades and fixations were detected using a velocity based algorithm and their properties analyzed. Results showed that there was no significant difference in the number of detected fixations but mean fixation durations differed between the 60 Hz mobile and the stationary eye tracker. The 120 Hz mobile eye tracker showed a significant increase in the detection rate of saccades and an improved estimation of the mean saccade duration, compared to the 60 Hz eye tracker. To conclude, for the detection and analysis of fast eye movements, such as saccades, it is better to use a 120 Hz mobile eye tracker

Depth of focus of the human eye - The transfer from objective data to subjective perception

Die vorliegende Arbeit umfasst Untersuchung der subjektiven und objektiven Sensitivität des visuellen Systems gegenüber verschiedenen optischen Aberrationen. Die Untersuchungen umfassten zum einen Messungen hinsichtlich der Auswirkungen des primären Astigmatismus auf die subjektive Schärfentiefe (sDoF). Zum anderen wurde die Bedeutung der individuellen neuronalen Übertragungsfunktion für die Vorhersagbarkeit der sDoF aus objektiven Defokuskurven, die aus Bildqualitätsmetriken berechnet wurden, behandelt. Des Weiteren wurden Untersuchungen zu möglichen Ursachen des Unterschiedes zwischen positivem und negativem sphärischem Defokus bezüglich der Reduktion der Sehschärfe durchgeführt

Peculiarities of structural-phase state of multi-layer coatings based on Zr-Y-O

Using high-resolution transmission electron microscopy it was established that the Zr-Y-O-based coating layers have a ZrO[2] phase in the tetragonal and monoclinic modifications in the initial state. When it is heated up to 900°C, the ZrO[2] phase in the cubic modification appears in the layer of the coating. With an annealing time of 20 minutes, the grains are crushed to a size of about 15-20 nm. The microdiffraction pattern is modified, the number of reflexes of the tetragonal and monoclinic phases first increases, and then changes without systemic

Accommodation lags are higher in myopia than in emmetropia:Measurement methods and metrics matter

Purpose: To determine whether accommodative errors in emmetropes and myopes are systematically different, and the effect of using different instruments and metrics. Methods: Seventy-six adults aged 18–27 years comprising 24 emmetropes (spherical equivalent refraction of the dominant eye +0.04 ± 0.03 D) and 52 myopes (−2.73 ± 0.22 D) were included. Accommodation responses were measured with a Grand Seiko WAM-5500 and a Hartmann–Shack Complete Ophthalmic Analysis System aberrometer, using pupil plane (Zernike and Seidel refraction) and retinal image plane (neural sharpness—NS; and visual Strehl ratio for modulation transfer function—VSMTF) metrics at 40, 33 and 25 cm. Accommodation stimuli were presented to the corrected dominant eye, and responses, referenced to the corneal plane, were determined in the fellow eye. Linear mixed-effects models were used to determine influence of the refractive group, the measurement method, accommodation stimulus, age, race, parental myopia, gender and binocular measures of heterophoria, accommodative convergence/accommodation and convergence accommodation/convergence ratios. Results: Lags of accommodation were affected significantly by the measurement method (p < 0.001), the refractive group (p = 0.003), near heterophoria (p = 0.002) and accommodative stimulus (p < 0.05), with significant interactions between some of these variables. Overall, emmetropes had smaller lags of accommodation than myopes with respective means ± standard errors of 0.31 ± 0.08 D and 0.61 ± 0.06 D (p = 0.003). Lags were largest for the Grand Seiko and Zernike defocus, intermediate for NS and VSMTF, and least for Seidel defocus. Conclusions: The mean lag of accommodation in emmetropes is approximately equal to the previously reported depth of focus. Myopes had larger (double) lags than emmetropes. Differences between methods and instruments could be as great as 0.50 D, and this must be considered when comparing studies and outcomes. Accommodative lag increased with the accommodation stimulus, but only for methods using a fixed small pupil diameter.</p

Imaginary systems? Conceptualizing hippocampal function beyond memory

Viewing the hippocampus as a structure specifically dedicated to memory is no longer viable. However, functional characterization of its structure and its involvement in learning and memory is still necessary. This review argues that the hippocampus principally processes specific spatial contexts. It highlights the hippocampal involvement in thinking about the future, rather than the past by discussing its role in episodic prospection and navigational planning. Finally, it argues that the hippocampus might also process non-spatial information by representing its components in a pseudo-Euclidean memory space.

Steps towards Smarter Solutions in Optometry and Ophthalmology—Inter-Device Agreement of Subjective Methods to Assess the Refractive Errors of the Eye

Purpose: To investigate the inter-device agreement and mean differences between a newly developed digital phoropter and the two standard methods (trial frame and manual phoropter). Methods: Refractive errors of two groups of participants were measured by two examiners (examiner 1 (E1): 36 subjects; examiner 2 (E2): 38 subjects). Refractive errors were assessed using a trial frame, a manual phoropter and a digital phoropter. Inter-device agreement regarding the measurement of refractive errors was analyzed for differences in terms of the power vector components (spherical equivalent (SE) and the cylindrical power vector components J0 and J45) between the used methods. Intraclass correlation coefficients (ICC’s) were calculated to evaluate correlations between the used methods. Results: Analyzing the variances between the three methods for SE, J0 and J45 using a two-way ANOVA showed no significant differences between the methods (SE: p = 0.13, J0: p = 0.58 and J45: p = 0.96) for examiner 1 and for examiner 2 (SE: p = 0.88, J0: p = 0.95 and J45: p = 1). Mean differences and ±95% Limits of Agreement for each pair of inter-device agreement regarding the SE for both examiners were as follows: Trial frame vs. digital phoropter: +0.10 D ± 0.56 D (E1) and +0.19 D ± 0.60 D (E2), manual phoropter vs. trial frame: −0.04 D ± 0.59 D (E1) and −0.12 D ± 0.49 D (E2) and for manual vs. digital phoropter: +0.06 D ± 0.65 D (E1) and +0.08 D ± 0.45 D (E2). ICCs revealed high correlations between all methods for both examiner (p &lt; 0.001). The time to assess the subjective refraction was significantly smaller with the digital phoropter (examiner 1: p &lt; 0.001; examiner 2: p &lt; 0.001). Conclusion: “All used subjective methods show a good agreement between each other terms of ICC (&gt;0.9). Assessing refractive errors using different subjective methods, results in similar mean differences and 95% limits of agreement, when compared to those reported in studies comparing subjective refraction non-cylcoplegic retinoscopy or autorefraction”