This cross-sectional study estimated computer vision syndrome (CVS) prevalence and analysed its relationship with video display terminal (VDT) exposure, as well as sociodemographic, refractive, environmental, and ergonomic characteristics in 109 presbyopic VDT workers wearing progressive addition lenses (PALs). Usual spectacles were measured with a lens analyser, and subjective refraction was performed by an optometrist. CVS was measured with the CVS-Q©. VDT exposure was collected. Ergonomic evaluations were conducted in a normal working posture looking at the screen. Air temperature and relative humidity were measured (thermohygrometer), and illumination was measured (luxmeter). Descriptive analysis and differences in CVS prevalence, as a function of the explanatory variables, were performed (chi-square test). Multivariate logistic regression was used to identify factors associated with CVS (OR and 95% CI). The mean age was 54.0 ± 4.8 years, and 43.1% were women. The mean hours of VDT use at work was 6.5 ± 1.3 hours/day. The prevalence of CVS was 74.3%. CVS was significantly associated with women (OR 3.40; 95% CI, 1.12–10.33), non-neutral neck posture (OR 3.27; 95% CI, 1.03–10.41) and altered workplace lighting (OR 3.64; 95% CI, 1.22–10.81). Providing training and information to workers regarding the importance of adequate lighting and ergonomic postures during VDT use is advised to decrease CVS and increase workplace quality of life.

Purpose: To estimate the prevalence of computer vision syndrome (CVS) in presbyopic digital device workers using two ophthalmic progressive lens designs during the working day, and to analyse the association of CVS with sociodemographic, occupational, digital device exposure and refractive factors. Methods: This time series, quasi-experimental design study included 69 presbyopic digital device workers (age range: 46-69 years; mean AE SD = 54.7 AE 5.0). All used desktop computers at their workplace. Progressive addition lenses (PALs) and occupational lenses were used for three months each. CVS was measured with the CVS-Q © questionnaire before intervention (baseline) and at 1 week, 1 month and 3 months after wearing the lenses. A multivariate logistic regression model was used to identify the factors that were associated with an improved CVS-Q © score. Results: 37.7% of the subjects were female and 78.3% were ametropes; 65.2% had advanced presbyopia. 56.2% used digital devices at work >6 h day À1 . The prevalence of CVS at baseline, after wearing PALs for three months and after three months of occupational lens wear was 68.1%, 33.3% and 18.8%, respectively. The mean CVS-Q © score was lower with occupational lenses than with PALs (p = 0.001). 40.6% of the digital device workers improved their CVS-Q © score ≥2 points with the occupational lenses. Ametropes were less likely than emmetropes to improve with occupational lenses (OR = 0.27, p = 0.05). 89.8% of the sample workers were satisfied or very satisfied with the occupational lenses and 71% were similarly satisfied with the PALs. 73.9% chose the occupational lenses as their first choice of lens for digital device use, compared with 17.4% for PALs. Conclusions: Computer vision syndrome is reduced in presbyopic desktop computer workers wearing occupational lenses compared with PALs, especially in emmetropes.

The evaluation of eye blinking has been used for the diagnosis of neurological disorders and fatigue. Despite the extensive literature, no objective method has been found to analyze its kinematic and dynamic behavior. A non-contact technique based on the high-speed recording of the light reflected by the eyelid in the blinking process and the off-line processing of the sequence is presented. It allows for objectively determining the start and end of a blink, besides obtaining different physical magnitudes: position, speed, eyelid acceleration as well as the power, work and mechanical impulse developed by the muscles involved in the physiological process. The parameters derived from these magnitudes provide a unique set of features that can be used to biometric authentication. This possibility has been tested with a limited number of subjects with a correct identification rate of up to 99.7%, thus showing the potential application of the method.

A knowledge of the shape of the cornea is of major importance for the planning and monitoring of surgery, and for the correct diagnosis of corneal diseases. Many authors have studied the geometry of the second corneal surface in the central region and it has been stated that there is a high correlation between the central radii of curvature and asphericities of the two corneal surfaces. In this work we extend this study to a larger, central, 6-mm diameter of the cornea. Surface height data, obtained with an Oculus Pentacam from 42 eyes from 21 subjects, were analysed to yield surface power vectors. Corneal heights of both surfaces were also decomposed into low-order Zernike polynomials and the correlations between each of the power vectors and low-order Zernike coefficients for the two surfaces were studied. There was not only a strong correlation between spherical powers and Zernike defocus coefficients, but also between the astigmatic components. The correspondence between the astigmatisms in both surfaces found here can be of the utmost importance in planning optical surgery, since perfect spherical ablation of the first surface does not assure total correction of corneal astigmatism.

Purpose: The aim of this study is to determine the reliability of corneal thickness measurements derived from SOCT Copernicus HR (Fourier domain OCT). Methods: Thirty healthy eyes of 30 subjects were evaluated. One eye of each patient was chosen randomly. Images were obtained of the central (up to 2.0 mm from the corneal apex) and paracentral (2.0 to 4.0 mm) cornea. We assessed corneal thickness (central and paracentral) and epithelium thickness. The intra-observer repeatability data were analysed using the intra-class correlation coefficient (ICC) for a range of 95 per cent within-subject standard deviation (SW) and the within-subject coefficient of variation (CW). The level of agreement by Bland-Altman analysis was also represented for the study of the reproducibility between observers and agreement between methods of measurement (automatic versus manual). Results: The mean value of the central corneal thickness (CCT) was 542.4 Ϯ 30.1 mm (SD). There was a high intra-observer agreement, finding the best result in the central sector with an intra-class correlation coefficient of 0.99, 95 per cent CI (0.989 to 0.997) and the worst, in the minimum corneal thickness, with an intra-class correlation coefficient of 0.672, 95 per cent CI (0.417 to 0.829). Reproducibility between observers was very high. The best result was found in the central sector thickness obtained both manually and automatically with an intra-class correlation coefficient of 0.990 in both cases and the worst result in the maximum corneal thickness with an intra-class correlation coefficient of 0.827. The agreement between measurement methods was also very high with intra-class correlation coefficient greater than 0.91. On the other hand the repeatability and reproducibility for epithelial measurements was poor. Conclusion: Pachymetric mapping with SOCT Copernicus HR was found to be highly repeatable and reproducible. We found that the device lacks an appropriate ergonomic design as proper focusing of the laser beam onto the cornea for anterior segment scanning required that patients were positioned slightly farther away from the machine head-rest than in the setup for retinal imaging.