Biomedical subjects

Manuel Melgosa

Publications and source records attributed to Manuel Melgosa.

4 recordsLinked to original sources

PubMed2006

Disinfecting solutions for soft contact lenses using different color indicators.

PURPOSE: The color change reached in two commercial disinfecting solutions for soft contact lenses using new color indicators has been analyzed, and its relationship with the temporal evolution of the hydrogen peroxide concentration, responsible for the disinfection process, has been examined. The results are compared with another commercial solution using a different color indicator. METHODS: Color measurements of the disinfecting solutions were performed at 2-minute intervals for over 2 hours using a Photo-Research PR-704 spectroradiometer with horizontal optical axis. Samples were placed at the floor of a VeriVide CAC 120 light booth with a Munsell gray mask behind them. Two different standard light sources, representative of outdoor and indoor illumination, were used. The hydrogen peroxide concentration during the disinfection process was measured for each commercial solution using a Beckman DU-7 spectrophotometer. RESULTS: The temporal evolutions of color for the two new disinfecting solutions were qualitatively different. CIELAB color differences induced in these two new disinfecting solutions were 1.5 and 2.2 times greater than that measured in the earlier comparative solution and occur in a more appropriate direction of color space for users with defective color vision. Although the earlier solution generated color changes close to the deutan confusion line, the changes produced by the new solutions are close to the tritan confusion line. After 2 hours, the hydrogen peroxide concentration for the two new solutions was approximately one-third the one reached by the earlier solution. There are statistically significant correlations (p < 0.01) between color change and hydrogen peroxide concentration for the two new solutions (r = -0.878 and r = -0.990). CONCLUSIONS: Color changes in these hydrogen peroxide systems can be used as a safe and useful tool by contact lens wearers. The two new disinfecting solutions analyzed in this article show noteworthy improvements over the earlier solution.

Color↗

PubMed2006

Influence of random-dot textures on perception of suprathreshold color differences.

We have analyzed the way in which simulated textures made of random dots influence visual suprathreshold color tolerances. We considered 32 textures created by a systematic variation of the following variables: size, number, and color of the dots. Each texture was mapped on the five centers recommended by the International Commission on Illumination (CIE) in 1978 [Color Res. Appl.3, 149 (1978)]. A panel of five experienced observers determined the experimental tolerances using a CRT color monitor by the method of adjustment. At our observation distance, neither small differences in dot size (1 or 4 pixels) nor sparse number of dots (less than 20% of the surface of the sample) changed the tolerances found for homogeneous samples. For the textures that led to statistically significant differences with respect to homogeneous samples, the parametric factors of CIEDE2000 and CIE94 color-difference formulas were fitted. These simulated textures consistently reduced the color difference perceived in a pair or, equivalently, increased the tolerances, mainly (but not only) lightness tolerance. The results demonstrate that it is not simple to provide a unique set of parametric factors for all the potential textures.

Color↗

PubMed2006

Performance of a color-difference formula based on OSA-UCS space using small-medium color differences.

An investigation of the color metrics and the complexity of the CIEDE2000 formula shows that CIELAB space is inadequate to represent small-medium color differences. The OSA-UCS (Uniform Color Space) Committee has shown that no space with uniform scale for large color differences exists. Therefore the practical way for color-difference specification is a color-difference formula in a nonuniform space. First, the BFD (Bradford University) ellipses are considered in the OSA-UCS space, and their very high regularity suggests a new and very simple color-difference formula at constant luminance. Then the COM (combined) data set used for the development of the CIEDE2000 formula is considered in the OSA-UCS space, and the color-difference formula is extended to sample pairs with a different luminance factor. The value of the performance factor PF/3 for the proposed OSA-UCS-based formula shows that the formula performs like the more complex CIEDE2000 formula for small-medium color differences.

Algorithms↗

PubMed2004

Relative significance of the terms in the CIEDE2000 and CIE94 color-difference formulas.

CIELAB-based color-difference formulas are used to improve the prediction of visually perceived color differences through the introduction of various corrections to CIELAB. In our study we analyze the relative importance of these corrections. From the combined dataset employed for the development of CIEDE2000, we found that the improvement of CIE94 over CIELAB was considerably greater than that of CIEDE2000 over CIE94. Chroma-difference correction was the most important correction in both CIE94 and CIEDE2000. With an arbitrary value of 100 assigned to this correction, the score of the hue-difference correction in CIE94 was 21, and the scores of the four remaining corrections in CIEDE2000 were as follows: hue difference, 29; rotation term, 8; lightness difference, 8; and gray correction, 6. At 95% confidence level each of the corrections introduced in CIEDE2000 or CIE94 was statistically significant for the whole combined dataset, in agreement with the results reported by CIE TC 1-47 and 1-29. For the combined dataset, the differences between CMC and CIEDE2000 were found to be statistically significant at 95% confidence level, but the differences between CMC and CIE94 were not. From subsets of the combined dataset it was concluded that further analyses of the lightness-difference and gray corrections proposed by CIEDE2000 would be desirable, using new experimental data.

Journal Article↗